Commit graph

2096 commits

Author SHA1 Message Date
Linus Torvalds
f5f59336a9 Updates for timekeeping, timers and related drivers:
Core:
 
   - Early boot support for the NMI safe timekeeper by utilizing
     local_clock() up to the point where timekeeping is initialized. This
     allows printk() to store multiple timestamps in the ringbuffer which is
     useful for coordinating dmesg information across a fleet of machines.
 
   - Provide a multi-timestamp accessor for printk()
 
   - Make timer init more robust by checking for invalid timer flags.
 
   - Comma vs. semicolon fixes
 
  Drivers:
 
   - Support for new platforms in existing drivers (SP804 and Renesas CMT)
 
   - Comma vs. semicolon fixes
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Merge tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping updates from Thomas Gleixner:
 "Updates for timekeeping, timers and related drivers:

  Core:

   - Early boot support for the NMI safe timekeeper by utilizing
     local_clock() up to the point where timekeeping is initialized.
     This allows printk() to store multiple timestamps in the ringbuffer
     which is useful for coordinating dmesg information across a fleet
     of machines.

   - Provide a multi-timestamp accessor for printk()

   - Make timer init more robust by checking for invalid timer flags.

   - Comma vs semicolon fixes

  Drivers:

   - Support for new platforms in existing drivers (SP804 and Renesas
     CMT)

   - Comma vs semicolon fixes

* tag 'timers-core-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource/drivers/armada-370-xp: Use semicolons rather than commas to separate statements
  clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements
  timers: Mask invalid flags in do_init_timer()
  clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode
  clocksource/drivers/sp804: Add support for Hisilicon sp804 timer
  clocksource/drivers/sp804: Support non-standard register offset
  clocksource/drivers/sp804: Prepare for support non-standard register offset
  clocksource/drivers/sp804: Remove a mismatched comment
  clocksource/drivers/sp804: Delete the leading "__" of some functions
  clocksource/drivers/sp804: Remove unused sp804_timer_disable() and timer-sp804.h
  clocksource/drivers/sp804: Cleanup clk_get_sys()
  dt-bindings: timer: renesas,cmt: Document r8a774e1 CMT support
  dt-bindings: timer: renesas,cmt: Document r8a7742 CMT support
  alarmtimer: Convert comma to semicolon
  timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
  timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
2020-10-12 11:27:54 -07:00
Ingo Molnar
e705d39796 Merge branch 'locking/urgent' into locking/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-10-09 08:55:17 +02:00
Ingo Molnar
b36c830f8c Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull v5.10 RCU changes from Paul E. McKenney:

- Debugging for smp_call_function().

- Strict grace periods for KASAN.  The point of this series is to find
  RCU-usage bugs, so the corresponding new RCU_STRICT_GRACE_PERIOD
  Kconfig option depends on both DEBUG_KERNEL and RCU_EXPERT, and is
  further disabled by dfefault.  Finally, the help text includes
  a goodly list of scary caveats.

- New smp_call_function() torture test.

- Torture-test updates.

- Documentation updates.

- Miscellaneous fixes.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-10-09 08:21:56 +02:00
Qianli Zhao
b952caf2d5 timers: Mask invalid flags in do_init_timer()
do_init_timer() accepts any combination of timer flags handed in by the
caller without a sanity check, but only TIMER_DEFFERABLE, TIMER_PINNED and
TIMER_IRQSAFE are valid.

If the supplied flags have other bits set, this could result in
malfunction. If bits are set in TIMER_CPUMASK the first timer usage could
deference a cpu base which is outside the range of possible CPUs. If
TIMER_MIGRATION is set, then the switch_timer_base() will live lock.

Prevent that with a sanity check which warns when invalid flags are
supplied and masks them out.

[ tglx: Made it WARN_ON_ONCE() and added context to the changelog ]

Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/9d79a8aa4eb56713af7379f99f062dedabcde140.1597326756.git.zhaoqianli@xiaomi.com
2020-09-24 22:12:18 +02:00
Stephen Boyd
f9e62f318f treewide: Make all debug_obj_descriptors const
This should make it harder for the kernel to corrupt the debug object
descriptor, used to call functions to fixup state and track debug objects,
by moving the structure to read-only memory.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20200815004027.2046113-3-swboyd@chromium.org
2020-09-24 21:56:25 +02:00
Ahmed S. Darwish
249d053835 timekeeping: Use seqcount_latch_t
Latch sequence counters are a multiversion concurrency control mechanism
where the seqcount_t counter even/odd value is used to switch between
two data storage copies. This allows the seqcount_t read path to safely
interrupt its write side critical section (e.g. from NMIs).

Initially, latch sequence counters were implemented as a single write
function, raw_write_seqcount_latch(), above plain seqcount_t. The read
path was expected to use plain seqcount_t raw_read_seqcount().

A specialized read function was later added, raw_read_seqcount_latch(),
and became the standardized way for latch read paths. Having unique read
and write APIs meant that latch sequence counters are basically a data
type of their own -- just inappropriately overloading plain seqcount_t.
The seqcount_latch_t data type was thus introduced at seqlock.h.

Use that new data type instead of seqcount_raw_spinlock_t. This ensures
that only latch-safe APIs are to be used with the sequence counter.

Note that the use of seqcount_raw_spinlock_t was not very useful in the
first place. Only the "raw_" subset of seqcount_t APIs were used at
timekeeping.c. This subset was created for contexts where lockdep cannot
be used. seqcount_LOCKTYPE_t's raison d'être -- verifying that the
seqcount_t writer serialization lock is held -- cannot thus be done.

References: 0c3351d451 ("seqlock: Use raw_ prefix instead of _no_lockdep")
References: 55f3560df9 ("seqlock: Extend seqcount API with associated locks")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-6-a.darwish@linutronix.de
2020-09-10 11:19:29 +02:00
Ahmed S. Darwish
a690ed0735 time/sched_clock: Use seqcount_latch_t
Latch sequence counters have unique read and write APIs, and thus
seqcount_latch_t was recently introduced at seqlock.h.

Use that new data type instead of plain seqcount_t. This adds the
necessary type-safety and ensures only latching-safe seqcount APIs are
to be used.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200827114044.11173-5-a.darwish@linutronix.de
2020-09-10 11:19:29 +02:00
Ahmed S. Darwish
58faf20a08 time/sched_clock: Use raw_read_seqcount_latch() during suspend
sched_clock uses seqcount_t latching to switch between two storage
places protected by the sequence counter. This allows it to have
interruptible, NMI-safe, seqcount_t write side critical sections.

Since 7fc26327b7 ("seqlock: Introduce raw_read_seqcount_latch()"),
raw_read_seqcount_latch() became the standardized way for seqcount_t
latch read paths. Due to the dependent load, it has one read memory
barrier less than the currently used raw_read_seqcount() API.

Use raw_read_seqcount_latch() for the suspend path.

Commit aadd6e5caa ("time/sched_clock: Use raw_read_seqcount_latch()")
missed changing that instance of raw_read_seqcount().

References: 1809bfa44e ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
2020-09-10 11:19:28 +02:00
Xu Wang
ec02821c1d alarmtimer: Convert comma to semicolon
Replace a comma between expression statements by a semicolon.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lore.kernel.org/r/20200818062651.21680-1-vulab@iscas.ac.cn
2020-08-25 12:45:53 +02:00
Paul E. McKenney
bca37119c5 tick-sched: Clarify "NOHZ: local_softirq_pending" warning
Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH"
(where "HH" is the hexadecimal softirq vector number) when one or more
non-RCU softirq handlers are still enabled when checking to stop the
scheduler-tick interrupt.  This message is not as enlightening as one
might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU
local softirq work is pending, handler #HH".

Reported-by: Andy Lutomirski <luto@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24 18:38:32 -07:00
Gustavo A. R. Silva
df561f6688 treewide: Use fallthrough pseudo-keyword
Replace the existing /* fall through */ comments and its variants with
the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary
fall-through markings when it is the case.

[1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
2020-08-23 17:36:59 -05:00
Thomas Gleixner
e2d977c9f1 timekeeping: Provide multi-timestamp accessor to NMI safe timekeeper
printk wants to store various timestamps (MONOTONIC, REALTIME, BOOTTIME) to
make correlation of dmesg from several systems easier.

Provide an interface to retrieve all three timestamps in one go.

There are some caveats:

1) Boot time and late sleep time injection

  Boot time is a racy access on 32bit systems if the sleep time injection
  happens late during resume and not in timekeeping_resume(). That could be
  avoided by expanding struct tk_read_base with boot offset for 32bit and
  adding more overhead to the update. As this is a hard to observe once per
  resume event which can be filtered with reasonable effort using the
  accurate mono/real timestamps, it's probably not worth the trouble.

  Aside of that it might be possible on 32 and 64 bit to observe the
  following when the sleep time injection happens late:

  CPU 0				         CPU 1
  timekeeping_resume()
  ktime_get_fast_timestamps()
    mono, real = __ktime_get_real_fast()
  					 inject_sleep_time()
  					   update boot offset
  	boot = mono + bootoffset;
  
  That means that boot time already has the sleep time adjustment, but
  real time does not. On the next readout both are in sync again.
  
  Preventing this for 64bit is not really feasible without destroying the
  careful cache layout of the timekeeper because the sequence count and
  struct tk_read_base would then need two cache lines instead of one.

2) Suspend/resume timestamps

   Access to the time keeper clock source is disabled accross the innermost
   steps of suspend/resume. The accessors still work, but the timestamps
   are frozen until time keeping is resumed which happens very early.

   For regular suspend/resume there is no observable difference vs. sched
   clock, but it might affect some of the nasty low level debug printks.

   OTOH, access to sched clock is not guaranteed accross suspend/resume on
   all systems either so it depends on the hardware in use.

   If that turns out to be a real problem then this could be mitigated by
   using sched clock in a similar way as during early boot. But it's not as
   trivial as on early boot because it needs some careful protection
   against the clock monotonic timestamp jumping backwards on resume.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>                                                                                                                                                                                                                                      
Link: https://lore.kernel.org/r/20200814115512.159981360@linutronix.de
2020-08-23 10:38:24 +02:00
Thomas Gleixner
71419b30ca timekeeping: Utilize local_clock() for NMI safe timekeeper during early boot
During early boot the NMI safe timekeeper returns 0 until the first
clocksource becomes available.

This prevents it from being used for printk or other facilities which today
use sched clock. sched clock can be available way before timekeeping is
initialized.

The obvious workaround for this is to utilize the early sched clock in the
default dummy clock read function until a clocksource becomes available.

After switching to the clocksource clock MONOTONIC and BOOTTIME will not
jump because the timekeeping_init() bases clock MONOTONIC on sched clock
and the offset between clock MONOTONIC and BOOTTIME is zero during boot.

Clock REALTIME cannot provide useful timestamps during early boot up to
the point where a persistent clock becomes available, which is either in
timekeeping_init() or later when the RTC driver which might depend on I2C
or other subsystems is initialized.

There is a minor difference to sched_clock() vs. suspend/resume. As the
timekeeper clock source might not be accessible during suspend, after
timekeeping_suspend() timestamps freeze up to the point where
timekeeping_resume() is invoked. OTOH this is true for some sched clock
implementations as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Petr Mladek <pmladek@suse.com>                                                                                                                                                                                                                                      
Link: https://lore.kernel.org/r/20200814115512.041422402@linutronix.de
2020-08-23 10:38:24 +02:00
Kirill Tkhai
28c41efd08
time: Use generic ns_common::count
Switch over time namespaces to use the newly introduced common lifetime
counter.

Currently every namespace type has its own lifetime counter which is stored
in the specific namespace struct. The lifetime counters are used
identically for all namespaces types. Namespaces may of course have
additional unrelated counters and these are not altered.

This introduces a common lifetime counter into struct ns_common. The
ns_common struct encompasses information that all namespaces share. That
should include the lifetime counter since its common for all of them.

It also allows us to unify the type of the counters across all namespaces.
Most of them use refcount_t but one uses atomic_t and at least one uses
kref. Especially the last one doesn't make much sense since it's just a
wrapper around refcount_t since 2016 and actually complicates cleanup
operations by having to use container_of() to cast the correct namespace
struct out of struct ns_common.

Having the lifetime counter for the namespaces in one place reduces
maintenance cost. Not just because after switching all namespaces over we
will have removed more code than we added but also because the logic is
more easily understandable and we indicate to the user that the basic
lifetime requirements for all namespaces are currently identical.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/159644982033.604812.9406853013011123238.stgit@localhost.localdomain
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
2020-08-19 14:14:35 +02:00
Linus Torvalds
b923f1247b A set oftimekeeping/VDSO updates:
- Preparatory work to allow S390 to switch over to the generic VDSO
    implementation.
 
    S390 requires that the VDSO data pointer is handed in to the counter
    read function when time namespace support is enabled. Adding the pointer
    is a NOOP for all other architectures because the compiler is supposed
    to optimize that out when it is unused in the architecture specific
    inline. The change also solved a similar problem for MIPS which
    fortunately has time namespaces not yet enabled.
 
    S390 needs to update clock related VDSO data independent of the
    timekeeping updates. This was solved so far with yet another sequence
    counter in the S390 implementation. A better solution is to utilize the
    already existing VDSO sequence count for this. The core code now exposes
    helper functions which allow to serialize against the timekeeper code
    and against concurrent readers.
 
    S390 needs extra data for their clock readout function. The initial
    common VDSO data structure did not provide a way to add that. It now has
    an embedded architecture specific struct embedded which defaults to an
    empty struct.
 
    Doing this now avoids tree dependencies and conflicts post rc1 and
    allows all other architectures which work on generic VDSO support to
    work from a common upstream base.
 
  - A trivial comment fix.
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Merge tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping updates from Thomas Gleixner:
 "A set of timekeeping/VDSO updates:

   - Preparatory work to allow S390 to switch over to the generic VDSO
     implementation.

     S390 requires that the VDSO data pointer is handed in to the
     counter read function when time namespace support is enabled.
     Adding the pointer is a NOOP for all other architectures because
     the compiler is supposed to optimize that out when it is unused in
     the architecture specific inline. The change also solved a similar
     problem for MIPS which fortunately has time namespaces not yet
     enabled.

     S390 needs to update clock related VDSO data independent of the
     timekeeping updates. This was solved so far with yet another
     sequence counter in the S390 implementation. A better solution is
     to utilize the already existing VDSO sequence count for this. The
     core code now exposes helper functions which allow to serialize
     against the timekeeper code and against concurrent readers.

     S390 needs extra data for their clock readout function. The initial
     common VDSO data structure did not provide a way to add that. It
     now has an embedded architecture specific struct embedded which
     defaults to an empty struct.

     Doing this now avoids tree dependencies and conflicts post rc1 and
     allows all other architectures which work on generic VDSO support
     to work from a common upstream base.

   - A trivial comment fix"

* tag 'timers-urgent-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  time: Delete repeated words in comments
  lib/vdso: Allow to add architecture-specific vdso data
  timekeeping/vsyscall: Provide vdso_update_begin/end()
  vdso/treewide: Add vdso_data pointer argument to __arch_get_hw_counter()
2020-08-14 14:26:08 -07:00
Linus Torvalds
b6b178e38f A set of posix CPU timer changes which allows to defer the heavy work of
posix CPU timers into task work context. The tick interrupt is reduced to a
 quick check which queues the work which is doing the heavy lifting before
 returning to user space or going back to guest mode. Moving this out is
 deferring the signal delivery slightly but posix CPU timers are inaccurate
 by nature as they depend on the tick so there is no real damage. The
 relevant test cases all passed.
 
 This lifts the last offender for RT out of the hard interrupt context tick
 handler, but it also has the general benefit that the actual heavy work is
 accounted to the task/process and not to the tick interrupt itself.
 
 Further optimizations are possible to break long sighand lock hold and
 interrupt disabled (on !RT kernels) times when a massive amount of posix
 CPU timers (which are unpriviledged) is armed for a task/process.
 
 This is currently only enabled for x86 because the architecture has to
 ensure that task work is handled in KVM before entering a guest, which was
 just established for x86 with the new common entry/exit code which got
 merged post 5.8 and is not the case for other KVM architectures.
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Merge tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more timer updates from Thomas Gleixner:
 "A set of posix CPU timer changes which allows to defer the heavy work
  of posix CPU timers into task work context. The tick interrupt is
  reduced to a quick check which queues the work which is doing the
  heavy lifting before returning to user space or going back to guest
  mode. Moving this out is deferring the signal delivery slightly but
  posix CPU timers are inaccurate by nature as they depend on the tick
  so there is no real damage. The relevant test cases all passed.

  This lifts the last offender for RT out of the hard interrupt context
  tick handler, but it also has the general benefit that the actual
  heavy work is accounted to the task/process and not to the tick
  interrupt itself.

  Further optimizations are possible to break long sighand lock hold and
  interrupt disabled (on !RT kernels) times when a massive amount of
  posix CPU timers (which are unpriviledged) is armed for a
  task/process.

  This is currently only enabled for x86 because the architecture has to
  ensure that task work is handled in KVM before entering a guest, which
  was just established for x86 with the new common entry/exit code which
  got merged post 5.8 and is not the case for other KVM architectures"

* tag 'timers-core-2020-08-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86: Select POSIX_CPU_TIMERS_TASK_WORK
  posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
  posix-cpu-timers: Split run_posix_cpu_timers()
2020-08-14 14:17:51 -07:00
Linus Torvalds
97d052ea3f A set of locking fixes and updates:
- Untangle the header spaghetti which causes build failures in various
     situations caused by the lockdep additions to seqcount to validate that
     the write side critical sections are non-preemptible.
 
   - The seqcount associated lock debug addons which were blocked by the
     above fallout.
 
     seqcount writers contrary to seqlock writers must be externally
     serialized, which usually happens via locking - except for strict per
     CPU seqcounts. As the lock is not part of the seqcount, lockdep cannot
     validate that the lock is held.
 
     This new debug mechanism adds the concept of associated locks.
     sequence count has now lock type variants and corresponding
     initializers which take a pointer to the associated lock used for
     writer serialization. If lockdep is enabled the pointer is stored and
     write_seqcount_begin() has a lockdep assertion to validate that the
     lock is held.
 
     Aside of the type and the initializer no other code changes are
     required at the seqcount usage sites. The rest of the seqcount API is
     unchanged and determines the type at compile time with the help of
     _Generic which is possible now that the minimal GCC version has been
     moved up.
 
     Adding this lockdep coverage unearthed a handful of seqcount bugs which
     have been addressed already independent of this.
 
     While generaly useful this comes with a Trojan Horse twist: On RT
     kernels the write side critical section can become preemtible if the
     writers are serialized by an associated lock, which leads to the well
     known reader preempts writer livelock. RT prevents this by storing the
     associated lock pointer independent of lockdep in the seqcount and
     changing the reader side to block on the lock when a reader detects
     that a writer is in the write side critical section.
 
  - Conversion of seqcount usage sites to associated types and initializers.
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Merge tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Thomas Gleixner:
 "A set of locking fixes and updates:

   - Untangle the header spaghetti which causes build failures in
     various situations caused by the lockdep additions to seqcount to
     validate that the write side critical sections are non-preemptible.

   - The seqcount associated lock debug addons which were blocked by the
     above fallout.

     seqcount writers contrary to seqlock writers must be externally
     serialized, which usually happens via locking - except for strict
     per CPU seqcounts. As the lock is not part of the seqcount, lockdep
     cannot validate that the lock is held.

     This new debug mechanism adds the concept of associated locks.
     sequence count has now lock type variants and corresponding
     initializers which take a pointer to the associated lock used for
     writer serialization. If lockdep is enabled the pointer is stored
     and write_seqcount_begin() has a lockdep assertion to validate that
     the lock is held.

     Aside of the type and the initializer no other code changes are
     required at the seqcount usage sites. The rest of the seqcount API
     is unchanged and determines the type at compile time with the help
     of _Generic which is possible now that the minimal GCC version has
     been moved up.

     Adding this lockdep coverage unearthed a handful of seqcount bugs
     which have been addressed already independent of this.

     While generally useful this comes with a Trojan Horse twist: On RT
     kernels the write side critical section can become preemtible if
     the writers are serialized by an associated lock, which leads to
     the well known reader preempts writer livelock. RT prevents this by
     storing the associated lock pointer independent of lockdep in the
     seqcount and changing the reader side to block on the lock when a
     reader detects that a writer is in the write side critical section.

   - Conversion of seqcount usage sites to associated types and
     initializers"

* tag 'locking-urgent-2020-08-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  locking/seqlock, headers: Untangle the spaghetti monster
  locking, arch/ia64: Reduce <asm/smp.h> header dependencies by moving XTP bits into the new <asm/xtp.h> header
  x86/headers: Remove APIC headers from <asm/smp.h>
  seqcount: More consistent seqprop names
  seqcount: Compress SEQCNT_LOCKNAME_ZERO()
  seqlock: Fold seqcount_LOCKNAME_init() definition
  seqlock: Fold seqcount_LOCKNAME_t definition
  seqlock: s/__SEQ_LOCKDEP/__SEQ_LOCK/g
  hrtimer: Use sequence counter with associated raw spinlock
  kvm/eventfd: Use sequence counter with associated spinlock
  userfaultfd: Use sequence counter with associated spinlock
  NFSv4: Use sequence counter with associated spinlock
  iocost: Use sequence counter with associated spinlock
  raid5: Use sequence counter with associated spinlock
  vfs: Use sequence counter with associated spinlock
  timekeeping: Use sequence counter with associated raw spinlock
  xfrm: policy: Use sequence counters with associated lock
  netfilter: nft_set_rbtree: Use sequence counter with associated rwlock
  netfilter: conntrack: Use sequence counter with associated spinlock
  sched: tasks: Use sequence counter with associated spinlock
  ...
2020-08-10 19:07:44 -07:00
Randy Dunlap
b0294f3025 time: Delete repeated words in comments
Drop repeated words in kernel/time/.  {when, one, into}

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Link: https://lore.kernel.org/r/20200807033248.8452-1-rdunlap@infradead.org
2020-08-10 22:14:07 +02:00
Thomas Gleixner
1fb497dd00 posix-cpu-timers: Provide mechanisms to defer timer handling to task_work
Running posix CPU timers in hard interrupt context has a few downsides:

 - For PREEMPT_RT it cannot work as the expiry code needs to take
   sighand lock, which is a 'sleeping spinlock' in RT. The original RT
   approach of offloading the posix CPU timer handling into a high
   priority thread was clumsy and provided no real benefit in general.

 - For fine grained accounting it's just wrong to run this in context of
   the timer interrupt because that way a process specific CPU time is
   accounted to the timer interrupt.

 - Long running timer interrupts caused by a large amount of expiring
   timers which can be created and armed by unpriviledged user space.

There is no hard requirement to expire them in interrupt context.

If the signal is targeted at the task itself then it won't be delivered
before the task returns to user space anyway. If the signal is targeted at
a supervisor process then it might be slightly delayed, but posix CPU
timers are inaccurate anyway due to the fact that they are tied to the
tick.

Provide infrastructure to schedule task work which allows splitting the
posix CPU timer code into a quick check in interrupt context and a thread
context expiry and signal delivery function. This has to be enabled by
architectures as it requires that the architecture specific KVM
implementation handles pending task work before exiting to guest mode.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.783470146@linutronix.de
2020-08-06 16:50:59 +02:00
Thomas Gleixner
820903c784 posix-cpu-timers: Split run_posix_cpu_timers()
Split it up as a preparatory step to move the heavy lifting out of
interrupt context.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200730102337.677439437@linutronix.de
2020-08-06 16:50:59 +02:00
Thomas Gleixner
19d0070a27 timekeeping/vsyscall: Provide vdso_update_begin/end()
Architectures can have the requirement to add additional architecture
specific data to the VDSO data page which needs to be updated independent
of the timekeeper updates.

To protect these updates vs. concurrent readers and a conflicting update
through timekeeping, provide helper functions to make such updates safe.

vdso_update_begin() takes the timekeeper_lock to protect against a
potential update from timekeeper code and increments the VDSO sequence
count to signal data inconsistency to concurrent readers. vdso_update_end()
makes the sequence count even again to signal data consistency and drops
the timekeeper lock.

[ Sven: Add interrupt disable handling to the functions ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200804150124.41692-3-svens@linux.ibm.com
2020-08-06 10:57:30 +02:00
Linus Torvalds
442489c219 Time, timers and related driver updates:
- Prevent unnecessary timer softirq invocations by extending the tracking
    of the next expiring timer in the timer wheel beyond the existing NOHZ
    functionality. The tracking overhead at enqueue time is within the
    noise, but on sensitive workloads the avoidance of the soft interrupt
    invocation is a measurable improvement.
 
  - The obligatory new clocksource driver for Ingenic X100 OST
 
  - The usual fixes, improvements, cleanups and extensions for newer chip
    variants all over the driver space.
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Merge tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer updates from Thomas Gleixner:
 "Time, timers and related driver updates:

   - Prevent unnecessary timer softirq invocations by extending the
     tracking of the next expiring timer in the timer wheel beyond the
     existing NOHZ functionality.

     The tracking overhead at enqueue time is within the noise, but on
     sensitive workloads the avoidance of the soft interrupt invocation
     is a measurable improvement.

   - The obligatory new clocksource driver for Ingenic X100 OST

   - The usual fixes, improvements, cleanups and extensions for newer
     chip variants all over the driver space"

* tag 'timers-core-2020-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (28 commits)
  timers: Recalculate next timer interrupt only when necessary
  clocksource/drivers/ingenic: Add support for the Ingenic X1000 OST.
  dt-bindings: timer: Add Ingenic X1000 OST bindings.
  clocksource/drivers: Replace HTTP links with HTTPS ones
  clocksource/drivers/nomadik-mtu: Handle 32kHz clock
  clocksource/drivers/sh_cmt: Use "kHz" for kilohertz
  clocksource/drivers/imx: Add support for i.MX TPM driver with ARM64
  clocksource/drivers/ingenic: Add high resolution timer support for SMP/SMT.
  timers: Lower base clock forwarding threshold
  timers: Remove must_forward_clk
  timers: Spare timer softirq until next expiry
  timers: Expand clk forward logic beyond nohz
  timers: Reuse next expiry cache after nohz exit
  timers: Always keep track of next expiry
  timers: Optimize _next_timer_interrupt() level iteration
  timers: Add comments about calc_index() ceiling work
  timers: Move trigger_dyntick_cpu() to enqueue_timer()
  timers: Use only bucket expiry for base->next_expiry value
  timers: Preserve higher bits of expiration on index calculation
  clocksource/drivers/timer-atmel-tcb: Add sama5d2 support
  ...
2020-08-04 18:17:37 -07:00
Linus Torvalds
0a72761b27 threads-v5.9
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Merge tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux

Pull thread updates from Christian Brauner:
 "This contains the changes to add the missing support for attaching to
  time namespaces via pidfds.

  Last cycle setns() was changed to support attaching to multiple
  namespaces atomically. This requires all namespaces to have a point of
  no return where they can't fail anymore.

  Specifically, <namespace-type>_install() is allowed to perform
  permission checks and install the namespace into the new struct nsset
  that it has been given but it is not allowed to make visible changes
  to the affected task. Once <namespace-type>_install() returns,
  anything that the given namespace type additionally requires to be
  setup needs to ideally be done in a function that can't fail or if it
  fails the failure must be non-fatal.

  For time namespaces the relevant functions that fell into this
  category were timens_set_vvar_page() and vdso_join_timens(). The
  latter could still fail although it didn't need to. This function is
  only implemented for vdso_join_timens() in current mainline. As
  discussed on-list (cf. [1]), in order to make setns() support time
  namespaces when attaching to multiple namespaces at once properly we
  changed vdso_join_timens() to always succeed. So vdso_join_timens()
  replaces the mmap_write_lock_killable() with mmap_read_lock().

  Please note that arm is about to grow vdso support for time namespaces
  (possibly this merge window). We've synced on this change and arm64
  also uses mmap_read_lock(), i.e. makes vdso_join_timens() a function
  that can't fail. Once the changes here and the arm64 changes have
  landed, vdso_join_timens() should be turned into a void function so
  it's obvious to callers and implementers on other architectures that
  the expectation is that it can't fail.

  We didn't do this right away because it would've introduced
  unnecessary merge conflicts between the two trees for no major gain.

  As always, tests included"

[1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein

* tag 'threads-v5.9' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  tests: add CLONE_NEWTIME setns tests
  nsproxy: support CLONE_NEWTIME with setns()
  timens: add timens_commit() helper
  timens: make vdso_join_timens() always succeed
2020-08-04 14:40:07 -07:00
Linus Torvalds
e4cbce4d13 The main changes in this cycle were:
- Improve uclamp performance by using a static key for the fast path
 
  - Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
    better power efficiency of RT tasks on battery powered devices.
    (The default is to maximize performance & reduce RT latencies.)
 
  - Improve utime and stime tracking accuracy, which had a fixed boundary
    of error, which created larger and larger relative errors as the values
    become larger. This is now replaced with more precise arithmetics,
    using the new mul_u64_u64_div_u64() helper in math64.h.
 
  - Improve the deadline scheduler, such as making it capacity aware
 
  - Improve frequency-invariant scheduling
 
  - Misc cleanups in energy/power aware scheduling
 
  - Add sched_update_nr_running tracepoint to track changes to nr_running
 
  - Documentation additions and updates
 
  - Misc cleanups and smaller fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:

 - Improve uclamp performance by using a static key for the fast path

 - Add the "sched_util_clamp_min_rt_default" sysctl, to optimize for
   better power efficiency of RT tasks on battery powered devices.
   (The default is to maximize performance & reduce RT latencies.)

 - Improve utime and stime tracking accuracy, which had a fixed boundary
   of error, which created larger and larger relative errors as the
   values become larger. This is now replaced with more precise
   arithmetics, using the new mul_u64_u64_div_u64() helper in math64.h.

 - Improve the deadline scheduler, such as making it capacity aware

 - Improve frequency-invariant scheduling

 - Misc cleanups in energy/power aware scheduling

 - Add sched_update_nr_running tracepoint to track changes to nr_running

 - Documentation additions and updates

 - Misc cleanups and smaller fixes

* tag 'sched-core-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst
  sched/doc: Document capacity aware scheduling
  sched: Document arch_scale_*_capacity()
  arm, arm64: Fix selection of CONFIG_SCHED_THERMAL_PRESSURE
  Documentation/sysctl: Document uclamp sysctl knobs
  sched/uclamp: Add a new sysctl to control RT default boost value
  sched/uclamp: Fix a deadlock when enabling uclamp static key
  sched: Remove duplicated tick_nohz_full_enabled() check
  sched: Fix a typo in a comment
  sched/uclamp: Remove unnecessary mutex_init()
  arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE
  sched: Cleanup SCHED_THERMAL_PRESSURE kconfig entry
  arch_topology, sched/core: Cleanup thermal pressure definition
  trace/events/sched.h: fix duplicated word
  linux/sched/mm.h: drop duplicated words in comments
  smp: Fix a potential usage of stale nr_cpus
  sched/fair: update_pick_idlest() Select group with lowest group_util when idle_cpus are equal
  sched: nohz: stop passing around unused "ticks" parameter.
  sched: Better document ttwu()
  sched: Add a tracepoint to track rq->nr_running
  ...
2020-08-03 14:58:38 -07:00
Linus Torvalds
8f0cb6660a These are the latest RCU bits for v5.9:
- kfree_rcu updates
   - RCU tasks updates
   - Read-side scalability tests
   - SRCU updates
   - Torture-test updates
   - Documentation updates
   - Miscellaneous fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU updates from Ingo Molnar:

 - kfree_rcu updates

 - RCU tasks updates

 - Read-side scalability tests

 - SRCU updates

 - Torture-test updates

 - Documentation updates

 - Miscellaneous fixes

* tag 'core-rcu-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (109 commits)
  torture: Remove obsolete "cd $KVM"
  torture: Avoid duplicate specification of qemu command
  torture: Dump ftrace at shutdown only if requested
  torture: Add kvm-tranform.sh script for qemu-cmd files
  torture: Add more tracing crib notes to kvm.sh
  torture: Improve diagnostic for KCSAN-incapable compilers
  torture: Correctly summarize build-only runs
  torture: Pass --kmake-arg to all make invocations
  rcutorture: Check for unwatched readers
  torture: Abstract out console-log error detection
  torture: Add a stop-run capability
  torture: Create qemu-cmd in --buildonly runs
  rcu/rcutorture: Replace 0 with false
  torture: Add --allcpus argument to the kvm.sh script
  torture: Remove whitespace from identify_qemu_vcpus output
  rcutorture: NULL rcu_torture_current earlier in cleanup code
  rcutorture: Handle non-statistic bang-string error messages
  torture: Set configfile variable to current scenario
  rcutorture: Add races with task-exit processing
  locktorture: Use true and false to assign to bool variables
  ...
2020-08-03 14:31:33 -07:00
Linus Torvalds
145ff1ec09 arm64 and cross-arch updates for 5.9:
- Removal of the tremendously unpopular read_barrier_depends() barrier,
   which is a NOP on all architectures apart from Alpha, in favour of
   allowing architectures to override READ_ONCE() and do whatever dance
   they need to do to ensure address dependencies provide LOAD ->
   LOAD/STORE ordering. This work also offers a potential solution if
   compilers are shown to convert LOAD -> LOAD address dependencies into
   control dependencies (e.g. under LTO), as weakly ordered architectures
   will effectively be able to upgrade READ_ONCE() to smp_load_acquire().
   The latter case is not used yet, but will be discussed further at LPC.
 
 - Make the MSI/IOMMU input/output ID translation PCI agnostic, augment
   the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
   bus-specific parameter and apply the resulting changes to the device
   ID space provided by the Freescale FSL bus.
 
 - arm64 support for TLBI range operations and translation table level
   hints (part of the ARMv8.4 architecture version).
 
 - Time namespace support for arm64.
 
 - Export the virtual and physical address sizes in vmcoreinfo for
   makedumpfile and crash utilities.
 
 - CPU feature handling cleanups and checks for programmer errors
   (overlapping bit-fields).
 
 - ACPI updates for arm64: disallow AML accesses to EFI code regions and
   kernel memory.
 
 - perf updates for arm64.
 
 - Miscellaneous fixes and cleanups, most notably PLT counting
   optimisation for module loading, recordmcount fix to ignore
   relocations other than R_AARCH64_CALL26, CMA areas reserved for
   gigantic pages on 16K and 64K configurations.
 
 - Trivial typos, duplicate words.
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Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 and cross-arch updates from Catalin Marinas:
 "Here's a slightly wider-spread set of updates for 5.9.

  Going outside the usual arch/arm64/ area is the removal of
  read_barrier_depends() series from Will and the MSI/IOMMU ID
  translation series from Lorenzo.

  The notable arm64 updates include ARMv8.4 TLBI range operations and
  translation level hint, time namespace support, and perf.

  Summary:

   - Removal of the tremendously unpopular read_barrier_depends()
     barrier, which is a NOP on all architectures apart from Alpha, in
     favour of allowing architectures to override READ_ONCE() and do
     whatever dance they need to do to ensure address dependencies
     provide LOAD -> LOAD/STORE ordering.

     This work also offers a potential solution if compilers are shown
     to convert LOAD -> LOAD address dependencies into control
     dependencies (e.g. under LTO), as weakly ordered architectures will
     effectively be able to upgrade READ_ONCE() to smp_load_acquire().
     The latter case is not used yet, but will be discussed further at
     LPC.

   - Make the MSI/IOMMU input/output ID translation PCI agnostic,
     augment the MSI/IOMMU ACPI/OF ID mapping APIs to accept an input ID
     bus-specific parameter and apply the resulting changes to the
     device ID space provided by the Freescale FSL bus.

   - arm64 support for TLBI range operations and translation table level
     hints (part of the ARMv8.4 architecture version).

   - Time namespace support for arm64.

   - Export the virtual and physical address sizes in vmcoreinfo for
     makedumpfile and crash utilities.

   - CPU feature handling cleanups and checks for programmer errors
     (overlapping bit-fields).

   - ACPI updates for arm64: disallow AML accesses to EFI code regions
     and kernel memory.

   - perf updates for arm64.

   - Miscellaneous fixes and cleanups, most notably PLT counting
     optimisation for module loading, recordmcount fix to ignore
     relocations other than R_AARCH64_CALL26, CMA areas reserved for
     gigantic pages on 16K and 64K configurations.

   - Trivial typos, duplicate words"

Link: http://lkml.kernel.org/r/20200710165203.31284-1-will@kernel.org
Link: http://lkml.kernel.org/r/20200619082013.13661-1-lorenzo.pieralisi@arm.com

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (82 commits)
  arm64: use IRQ_STACK_SIZE instead of THREAD_SIZE for irq stack
  arm64/mm: save memory access in check_and_switch_context() fast switch path
  arm64: sigcontext.h: delete duplicated word
  arm64: ptrace.h: delete duplicated word
  arm64: pgtable-hwdef.h: delete duplicated words
  bus: fsl-mc: Add ACPI support for fsl-mc
  bus/fsl-mc: Refactor the MSI domain creation in the DPRC driver
  of/irq: Make of_msi_map_rid() PCI bus agnostic
  of/irq: make of_msi_map_get_device_domain() bus agnostic
  dt-bindings: arm: fsl: Add msi-map device-tree binding for fsl-mc bus
  of/device: Add input id to of_dma_configure()
  of/iommu: Make of_map_rid() PCI agnostic
  ACPI/IORT: Add an input ID to acpi_dma_configure()
  ACPI/IORT: Remove useless PCI bus walk
  ACPI/IORT: Make iort_msi_map_rid() PCI agnostic
  ACPI/IORT: Make iort_get_device_domain IRQ domain agnostic
  ACPI/IORT: Make iort_match_node_callback walk the ACPI namespace for NC
  arm64: enable time namespace support
  arm64/vdso: Restrict splitting VVAR VMA
  arm64/vdso: Handle faults on timens page
  ...
2020-08-03 14:11:08 -07:00
Ingo Molnar
c1cc4784ce Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull the v5.9 RCU bits from Paul E. McKenney:

 - Documentation updates
 - Miscellaneous fixes
 - kfree_rcu updates
 - RCU tasks updates
 - Read-side scalability tests
 - SRCU updates
 - Torture-test updates

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-07-31 00:15:53 +02:00
Willy Tarreau
f227e3ec3b random32: update the net random state on interrupt and activity
This modifies the first 32 bits out of the 128 bits of a random CPU's
net_rand_state on interrupt or CPU activity to complicate remote
observations that could lead to guessing the network RNG's internal
state.

Note that depending on some network devices' interrupt rate moderation
or binding, this re-seeding might happen on every packet or even almost
never.

In addition, with NOHZ some CPUs might not even get timer interrupts,
leaving their local state rarely updated, while they are running
networked processes making use of the random state.  For this reason, we
also perform this update in update_process_times() in order to at least
update the state when there is user or system activity, since it's the
only case we care about.

Reported-by: Amit Klein <aksecurity@gmail.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-07-29 10:35:37 -07:00
Ahmed S. Darwish
af5a06b582 hrtimer: Use sequence counter with associated raw spinlock
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_raw_spinlock_t data type, which allows to associate
a raw spinlock with the sequence counter. This enables lockdep to verify
that the raw spinlock used for writer serialization is held when the
write side critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-25-a.darwish@linutronix.de
2020-07-29 16:14:29 +02:00
Ahmed S. Darwish
025e82bcbc timekeeping: Use sequence counter with associated raw spinlock
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_raw_spinlock_t data type, which allows to associate
a raw spinlock with the sequence counter. This enables lockdep to verify
that the raw spinlock used for writer serialization is held when the
write side critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-18-a.darwish@linutronix.de
2020-07-29 16:14:27 +02:00
Frederic Weisbecker
31cd0e119d timers: Recalculate next timer interrupt only when necessary
The nohz tick code recalculates the timer wheel's next expiry on each idle
loop iteration.

On the other hand, the base next expiry is now always cached and updated
upon timer enqueue and execution. Only timer dequeue may leave
base->next_expiry out of date (but then its stale value won't ever go past
the actual next expiry to be recalculated).

Since recalculating the next_expiry isn't a free operation, especially when
the last wheel level is reached to find out that no timer has been enqueued
at all, reuse the next expiry cache when it is known to be reliable, which
it is most of the time.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200723151641.12236-1-frederic@kernel.org
2020-07-24 12:49:40 +02:00
Paul Gortmaker
46132e3ac5 sched: nohz: stop passing around unused "ticks" parameter.
The "ticks" parameter was added in commit 0f004f5a69 ("sched: Cure more
NO_HZ load average woes") since calc_global_nohz() was called and needed
the "ticks" argument.

But in commit c308b56b53 ("sched: Fix nohz load accounting -- again!")
it became unused as the function calc_global_nohz() dropped using "ticks".

Fixes: c308b56b53 ("sched: Fix nohz load accounting -- again!")
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/1593628458-32290-1-git-send-email-paul.gortmaker@windriver.com
2020-07-22 10:22:04 +02:00
Ahmed S. Darwish
aadd6e5caa time/sched_clock: Use raw_read_seqcount_latch()
sched_clock uses seqcount_t latching to switch between two storage
places protected by the sequence counter. This allows it to have
interruptible, NMI-safe, seqcount_t write side critical sections.

Since 7fc26327b7 ("seqlock: Introduce raw_read_seqcount_latch()"),
raw_read_seqcount_latch() became the standardized way for seqcount_t
latch read paths. Due to the dependent load, it also has one read
memory barrier less than the currently used raw_read_seqcount() API.

Use raw_read_seqcount_latch() for the seqcount_t latch read path.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lkml.kernel.org/r/20200625085745.GD117543@hirez.programming.kicks-ass.net
Link: https://lkml.kernel.org/r/20200715092345.GA231464@debian-buster-darwi.lab.linutronix.de
Link: https://lore.kernel.org/r/20200716051130.4359-3-leo.yan@linaro.org
References: 1809bfa44e ("timers, sched/clock: Avoid deadlock during read from NMI")
Signed-off-by: Will Deacon <will@kernel.org>
2020-07-20 11:50:47 +01:00
Peter Zijlstra
1b86abc1c6 sched_clock: Expose struct clock_read_data
In order to support perf_event_mmap_page::cap_time features, an
architecture needs, aside from a userspace readable counter register,
to expose the exact clock data so that userspace can convert the
counter register into a correct timestamp.

Provide struct clock_read_data and two (seqcount) helpers so that
architectures (arm64 in specific) can expose the numbers to userspace.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Link: https://lore.kernel.org/r/20200716051130.4359-2-leo.yan@linaro.org
Signed-off-by: Will Deacon <will@kernel.org>
2020-07-20 11:50:47 +01:00
Frederic Weisbecker
36cd28a4cd timers: Lower base clock forwarding threshold
There is nothing that prevents from forwarding the base clock if it's one
jiffy off. The reason for this arbitrary limit of two jiffies is historical
and does not longer exist.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-13-frederic@kernel.org
2020-07-17 21:55:25 +02:00
Frederic Weisbecker
0975fb565b timers: Remove must_forward_clk
There is no reason to keep this guard around. The code makes sure that
base->clk remains sane and won't be forwarded beyond jiffies nor set
backward.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-12-frederic@kernel.org
2020-07-17 21:55:25 +02:00
Frederic Weisbecker
d4f7dae870 timers: Spare timer softirq until next expiry
Now that the core timer infrastructure doesn't depend anymore on
periodic base->clk increments, even when the CPU is not in NO_HZ mode,
timer softirqs can be skipped until there are timers to expire.

Some spurious softirqs can still remain since base->next_expiry doesn't
keep track of canceled timers but this still reduces the number of softirqs
significantly: ~15 times less for HZ=1000 and ~5 times less for HZ=100.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-11-frederic@kernel.org
2020-07-17 21:55:24 +02:00
Frederic Weisbecker
1f8a4212dc timers: Expand clk forward logic beyond nohz
As for next_expiry, the base->clk catch up logic will be expanded beyond
NOHZ in order to avoid triggering useless softirqs.

If softirqs should only fire to expire pending timers, periodic base->clk
increments must be skippable for random amounts of time.  Therefore prepare
to catch-up with missing updates whenever an up-to-date base clock is
needed.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-10-frederic@kernel.org
2020-07-17 21:55:24 +02:00
Frederic Weisbecker
90d52f65f3 timers: Reuse next expiry cache after nohz exit
Now that the next expiry it tracked unconditionally when a timer is added,
this information can be reused on a tick firing after exiting nohz.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-9-frederic@kernel.org
2020-07-17 21:55:23 +02:00
Frederic Weisbecker
dc2a0f1fb2 timers: Always keep track of next expiry
So far next expiry was only tracked while the CPU was in nohz_idle mode
in order to cope with missing ticks that can't increment the base->clk
periodically anymore.

This logic is going to be expanded beyond nohz in order to spare timer
softirqs so do it unconditionally.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-8-frederic@kernel.org
2020-07-17 21:55:23 +02:00
Frederic Weisbecker
001ec1b392 timers: Optimize _next_timer_interrupt() level iteration
If a level has a timer that expires before reaching the next level, there
is no need to iterate further.

The next level is reached when the 3 lower bits of the current level are
cleared. If the next event happens before/during that, the next levels
won't provide an earlier expiration.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-7-frederic@kernel.org
2020-07-17 21:55:22 +02:00
Frederic Weisbecker
4468897211 timers: Add comments about calc_index() ceiling work
calc_index() adds 1 unit of the level granularity to the expiry passed
in parameter to ensure that the timer doesn't expire too early. Add a
comment to explain that and the resulting layout in the wheel.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-6-frederic@kernel.org
2020-07-17 21:55:22 +02:00
Frederic Weisbecker
9a2b764b06 timers: Move trigger_dyntick_cpu() to enqueue_timer()
Consolidate the code by calling trigger_dyntick_cpu() from
enqueue_timer() instead of calling it from all its callers.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lkml.kernel.org/r/20200717140551.29076-5-frederic@kernel.org
2020-07-17 21:55:22 +02:00
Anna-Maria Behnsen
1f32cab0db timers: Use only bucket expiry for base->next_expiry value
The bucket expiry time is the effective expriy time of timers and is
greater than or equal to the requested timer expiry time. This is due
to the guarantee that timers never expire early and the reduced expiry
granularity in the secondary wheel levels.

When a timer is enqueued, trigger_dyntick_cpu() checks whether the
timer is the new first timer. This check compares next_expiry with
the requested timer expiry value and not with the effective expiry
value of the bucket into which the timer was queued.

Storing the requested timer expiry value in base->next_expiry can lead
to base->clk going backwards if the requested timer expiry value is
smaller than base->clk. Commit 30c66fc30e ("timer: Prevent base->clk
from moving backward") worked around this by preventing the store when
timer->expiry is before base->clk, but did not fix the underlying
problem.

Use the expiry value of the bucket into which the timer is queued to
do the new first timer check. This fixes the base->clk going backward
problem.

The workaround of commit 30c66fc30e ("timer: Prevent base->clk from
moving backward") in trigger_dyntick_cpu() is not longer necessary as the
timers bucket expiry is guaranteed to be greater than or equal base->clk.

Signed-off-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200717140551.29076-4-frederic@kernel.org
2020-07-17 21:55:21 +02:00
Frederic Weisbecker
3d2e83a2a6 timers: Preserve higher bits of expiration on index calculation
The higher bits of the timer expiration are cropped while calling
calc_index() due to the implicit cast from unsigned long to unsigned int.

This loss shouldn't have consequences on the current code since all the
computation to calculate the index is done on the lower 32 bits.

However to prepare for returning the actual bucket expiration from
calc_index() in order to properly fix base->next_expiry updates, the higher
bits need to be preserved.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200717140551.29076-3-frederic@kernel.org
2020-07-17 21:55:21 +02:00
Frederic Weisbecker
e2a71bdea8 timer: Fix wheel index calculation on last level
When an expiration delta falls into the last level of the wheel, that delta
has be compared against the maximum possible delay and reduced to fit in if
necessary.

However instead of comparing the delta against the maximum, the code
compares the actual expiry against the maximum. Then instead of fixing the
delta to fit in, it sets the maximum delta as the expiry value.

This can result in various undesired outcomes, the worst possible one
being a timer expiring 15 days ahead to fire immediately.

Fixes: 500462a9de ("timers: Switch to a non-cascading wheel")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200717140551.29076-2-frederic@kernel.org
2020-07-17 21:44:05 +02:00
Frederic Weisbecker
30c66fc30e timer: Prevent base->clk from moving backward
When a timer is enqueued with a negative delta (ie: expiry is below
base->clk), it gets added to the wheel as expiring now (base->clk).

Yet the value that gets stored in base->next_expiry, while calling
trigger_dyntick_cpu(), is the initial timer->expires value. The
resulting state becomes:

	base->next_expiry < base->clk

On the next timer enqueue, forward_timer_base() may accidentally
rewind base->clk. As a possible outcome, timers may expire way too
early, the worst case being that the highest wheel levels get spuriously
processed again.

To prevent from that, make sure that base->next_expiry doesn't get below
base->clk.

Fixes: a683f390b9 ("timers: Forward the wheel clock whenever possible")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200703010657.2302-1-frederic@kernel.org
2020-07-09 11:56:57 +02:00
Christian Brauner
76c12881a3
nsproxy: support CLONE_NEWTIME with setns()
So far setns() was missing time namespace support. This was partially due
to it simply not being implemented but also because vdso_join_timens()
could still fail which made switching to multiple namespaces atomically
problematic. This is now fixed so support CLONE_NEWTIME with setns()

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Dmitry Safonov <dima@arista.com>
Link: https://lore.kernel.org/r/20200706154912.3248030-4-christian.brauner@ubuntu.com
2020-07-08 11:14:22 +02:00
Christian Brauner
5cfea9a106
timens: add timens_commit() helper
Wrap the calls to timens_set_vvar_page() and vdso_join_timens() in
timens_on_fork() and timens_install() in a new timens_commit() helper.
We'll use this helper in a follow-up patch in nsproxy too.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Dmitry Safonov <dima@arista.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20200706154912.3248030-3-christian.brauner@ubuntu.com
2020-07-08 11:14:21 +02:00
Christian Brauner
42815808f1
timens: make vdso_join_timens() always succeed
As discussed on-list (cf. [1]), in order to make setns() support time
namespaces when attaching to multiple namespaces at once properly we
need to tweak vdso_join_timens() to always succeed. So switch
vdso_join_timens() to using a read lock and replacing
mmap_write_lock_killable() to mmap_read_lock() as we discussed.

Last cycle setns() was changed to support attaching to multiple namespaces
atomically. This requires all namespaces to have a point of no return where
they can't fail anymore. Specifically, <namespace-type>_install() is
allowed to perform permission checks and install the namespace into the new
struct nsset that it has been given but it is not allowed to make visible
changes to the affected task. Once <namespace-type>_install() returns
anything that the given namespace type requires to be setup in addition
needs to ideally be done in a function that can't fail or if it fails the
failure is not fatal. For time namespaces the relevant functions that fall
into this category are timens_set_vvar_page() and vdso_join_timens().
Currently the latter can fail but doesn't need to. With this we can go on
to implement a timens_commit() helper in a follow up patch to be used by
setns().

[1]: https://lore.kernel.org/lkml/20200611110221.pgd3r5qkjrjmfqa2@wittgenstein

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Dmitry Safonov <dima@arista.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: https://lore.kernel.org/r/20200706154912.3248030-2-christian.brauner@ubuntu.com
2020-07-08 11:14:21 +02:00
Frederic Weisbecker
3c8920e2db tick/nohz: Narrow down noise while setting current task's tick dependency
Setting a tick dependency on any task, including the case where a task
sets that dependency on itself, triggers an IPI to all CPUs.  That is
of course suboptimal but it had previously not been an issue because it
was only used by POSIX CPU timers on nohz_full, which apparently never
occurs in latency-sensitive workloads in production.  (Or users of such
systems are suffering in silence on the one hand or venting their ire
on the wrong people on the other.)

But RCU now sets a task tick dependency on the current task in order
to fix stall issues that can occur during RCU callback processing.
Thus, RCU callback processing triggers frequent system-wide IPIs from
nohz_full CPUs.  This is quite counter-productive, after all, avoiding
IPIs is what nohz_full is supposed to be all about.

This commit therefore optimizes tasks' self-setting of a task tick
dependency by using tick_nohz_full_kick() to avoid the system-wide IPI.
Instead, only the execution of the one task is disturbed, which is
acceptable given that this disturbance is well down into the noise
compared to the degree to which the RCU callback processing itself
disturbs execution.

Fixes: 6a949b7af8 (rcu: Force on tick when invoking lots of callbacks)
Reported-by: Matt Fleming <matt@codeblueprint.co.uk>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: stable@kernel.org
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29 11:58:50 -07:00
Linus Torvalds
076f14be7f The X86 entry, exception and interrupt code rework
This all started about 6 month ago with the attempt to move the Posix CPU
 timer heavy lifting out of the timer interrupt code and just have lockless
 quick checks in that code path. Trivial 5 patches.
 
 This unearthed an inconsistency in the KVM handling of task work and the
 review requested to move all of this into generic code so other
 architectures can share.
 
 Valid request and solved with another 25 patches but those unearthed
 inconsistencies vs. RCU and instrumentation.
 
 Digging into this made it obvious that there are quite some inconsistencies
 vs. instrumentation in general. The int3 text poke handling in particular
 was completely unprotected and with the batched update of trace events even
 more likely to expose to endless int3 recursion.
 
 In parallel the RCU implications of instrumenting fragile entry code came
 up in several discussions.
 
 The conclusion of the X86 maintainer team was to go all the way and make
 the protection against any form of instrumentation of fragile and dangerous
 code pathes enforcable and verifiable by tooling.
 
 A first batch of preparatory work hit mainline with commit d5f744f9a2.
 
 The (almost) full solution introduced a new code section '.noinstr.text'
 into which all code which needs to be protected from instrumentation of all
 sorts goes into. Any call into instrumentable code out of this section has
 to be annotated. objtool has support to validate this. Kprobes now excludes
 this section fully which also prevents BPF from fiddling with it and all
 'noinstr' annotated functions also keep ftrace off. The section, kprobes
 and objtool changes are already merged.
 
 The major changes coming with this are:
 
     - Preparatory cleanups
 
     - Annotating of relevant functions to move them into the noinstr.text
       section or enforcing inlining by marking them __always_inline so the
       compiler cannot misplace or instrument them.
 
     - Splitting and simplifying the idtentry macro maze so that it is now
       clearly separated into simple exception entries and the more
       interesting ones which use interrupt stacks and have the paranoid
       handling vs. CR3 and GS.
 
     - Move quite some of the low level ASM functionality into C code:
 
        - enter_from and exit to user space handling. The ASM code now calls
          into C after doing the really necessary ASM handling and the return
 	 path goes back out without bells and whistels in ASM.
 
        - exception entry/exit got the equivivalent treatment
 
        - move all IRQ tracepoints from ASM to C so they can be placed as
          appropriate which is especially important for the int3 recursion
          issue.
 
     - Consolidate the declaration and definition of entry points between 32
       and 64 bit. They share a common header and macros now.
 
     - Remove the extra device interrupt entry maze and just use the regular
       exception entry code.
 
     - All ASM entry points except NMI are now generated from the shared header
       file and the corresponding macros in the 32 and 64 bit entry ASM.
 
     - The C code entry points are consolidated as well with the help of
       DEFINE_IDTENTRY*() macros. This allows to ensure at one central point
       that all corresponding entry points share the same semantics. The
       actual function body for most entry points is in an instrumentable
       and sane state.
 
       There are special macros for the more sensitive entry points,
       e.g. INT3 and of course the nasty paranoid #NMI, #MCE, #DB and #DF.
       They allow to put the whole entry instrumentation and RCU handling
       into safe places instead of the previous pray that it is correct
       approach.
 
     - The INT3 text poke handling is now completely isolated and the
       recursion issue banned. Aside of the entry rework this required other
       isolation work, e.g. the ability to force inline bsearch.
 
     - Prevent #DB on fragile entry code, entry relevant memory and disable
       it on NMI, #MC entry, which allowed to get rid of the nested #DB IST
       stack shifting hackery.
 
     - A few other cleanups and enhancements which have been made possible
       through this and already merged changes, e.g. consolidating and
       further restricting the IDT code so the IDT table becomes RO after
       init which removes yet another popular attack vector
 
     - About 680 lines of ASM maze are gone.
 
 There are a few open issues:
 
    - An escape out of the noinstr section in the MCE handler which needs
      some more thought but under the aspect that MCE is a complete
      trainwreck by design and the propability to survive it is low, this was
      not high on the priority list.
 
    - Paravirtualization
 
      When PV is enabled then objtool complains about a bunch of indirect
      calls out of the noinstr section. There are a few straight forward
      ways to fix this, but the other issues vs. general correctness were
      more pressing than parawitz.
 
    - KVM
 
      KVM is inconsistent as well. Patches have been posted, but they have
      not yet been commented on or picked up by the KVM folks.
 
    - IDLE
 
      Pretty much the same problems can be found in the low level idle code
      especially the parts where RCU stopped watching. This was beyond the
      scope of the more obvious and exposable problems and is on the todo
      list.
 
 The lesson learned from this brain melting exercise to morph the evolved
 code base into something which can be validated and understood is that once
 again the violation of the most important engineering principle
 "correctness first" has caused quite a few people to spend valuable time on
 problems which could have been avoided in the first place. The "features
 first" tinkering mindset really has to stop.
 
 With that I want to say thanks to everyone involved in contributing to this
 effort. Special thanks go to the following people (alphabetical order):
 
    Alexandre Chartre
    Andy Lutomirski
    Borislav Petkov
    Brian Gerst
    Frederic Weisbecker
    Josh Poimboeuf
    Juergen Gross
    Lai Jiangshan
    Macro Elver
    Paolo Bonzini
    Paul McKenney
    Peter Zijlstra
    Vitaly Kuznetsov
    Will Deacon
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Merge tag 'x86-entry-2020-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 entry updates from Thomas Gleixner:
 "The x86 entry, exception and interrupt code rework

  This all started about 6 month ago with the attempt to move the Posix
  CPU timer heavy lifting out of the timer interrupt code and just have
  lockless quick checks in that code path. Trivial 5 patches.

  This unearthed an inconsistency in the KVM handling of task work and
  the review requested to move all of this into generic code so other
  architectures can share.

  Valid request and solved with another 25 patches but those unearthed
  inconsistencies vs. RCU and instrumentation.

  Digging into this made it obvious that there are quite some
  inconsistencies vs. instrumentation in general. The int3 text poke
  handling in particular was completely unprotected and with the batched
  update of trace events even more likely to expose to endless int3
  recursion.

  In parallel the RCU implications of instrumenting fragile entry code
  came up in several discussions.

  The conclusion of the x86 maintainer team was to go all the way and
  make the protection against any form of instrumentation of fragile and
  dangerous code pathes enforcable and verifiable by tooling.

  A first batch of preparatory work hit mainline with commit
  d5f744f9a2 ("Pull x86 entry code updates from Thomas Gleixner")

  That (almost) full solution introduced a new code section
  '.noinstr.text' into which all code which needs to be protected from
  instrumentation of all sorts goes into. Any call into instrumentable
  code out of this section has to be annotated. objtool has support to
  validate this.

  Kprobes now excludes this section fully which also prevents BPF from
  fiddling with it and all 'noinstr' annotated functions also keep
  ftrace off. The section, kprobes and objtool changes are already
  merged.

  The major changes coming with this are:

    - Preparatory cleanups

    - Annotating of relevant functions to move them into the
      noinstr.text section or enforcing inlining by marking them
      __always_inline so the compiler cannot misplace or instrument
      them.

    - Splitting and simplifying the idtentry macro maze so that it is
      now clearly separated into simple exception entries and the more
      interesting ones which use interrupt stacks and have the paranoid
      handling vs. CR3 and GS.

    - Move quite some of the low level ASM functionality into C code:

       - enter_from and exit to user space handling. The ASM code now
         calls into C after doing the really necessary ASM handling and
         the return path goes back out without bells and whistels in
         ASM.

       - exception entry/exit got the equivivalent treatment

       - move all IRQ tracepoints from ASM to C so they can be placed as
         appropriate which is especially important for the int3
         recursion issue.

    - Consolidate the declaration and definition of entry points between
      32 and 64 bit. They share a common header and macros now.

    - Remove the extra device interrupt entry maze and just use the
      regular exception entry code.

    - All ASM entry points except NMI are now generated from the shared
      header file and the corresponding macros in the 32 and 64 bit
      entry ASM.

    - The C code entry points are consolidated as well with the help of
      DEFINE_IDTENTRY*() macros. This allows to ensure at one central
      point that all corresponding entry points share the same
      semantics. The actual function body for most entry points is in an
      instrumentable and sane state.

      There are special macros for the more sensitive entry points, e.g.
      INT3 and of course the nasty paranoid #NMI, #MCE, #DB and #DF.
      They allow to put the whole entry instrumentation and RCU handling
      into safe places instead of the previous pray that it is correct
      approach.

    - The INT3 text poke handling is now completely isolated and the
      recursion issue banned. Aside of the entry rework this required
      other isolation work, e.g. the ability to force inline bsearch.

    - Prevent #DB on fragile entry code, entry relevant memory and
      disable it on NMI, #MC entry, which allowed to get rid of the
      nested #DB IST stack shifting hackery.

    - A few other cleanups and enhancements which have been made
      possible through this and already merged changes, e.g.
      consolidating and further restricting the IDT code so the IDT
      table becomes RO after init which removes yet another popular
      attack vector

    - About 680 lines of ASM maze are gone.

  There are a few open issues:

   - An escape out of the noinstr section in the MCE handler which needs
     some more thought but under the aspect that MCE is a complete
     trainwreck by design and the propability to survive it is low, this
     was not high on the priority list.

   - Paravirtualization

     When PV is enabled then objtool complains about a bunch of indirect
     calls out of the noinstr section. There are a few straight forward
     ways to fix this, but the other issues vs. general correctness were
     more pressing than parawitz.

   - KVM

     KVM is inconsistent as well. Patches have been posted, but they
     have not yet been commented on or picked up by the KVM folks.

   - IDLE

     Pretty much the same problems can be found in the low level idle
     code especially the parts where RCU stopped watching. This was
     beyond the scope of the more obvious and exposable problems and is
     on the todo list.

  The lesson learned from this brain melting exercise to morph the
  evolved code base into something which can be validated and understood
  is that once again the violation of the most important engineering
  principle "correctness first" has caused quite a few people to spend
  valuable time on problems which could have been avoided in the first
  place. The "features first" tinkering mindset really has to stop.

  With that I want to say thanks to everyone involved in contributing to
  this effort. Special thanks go to the following people (alphabetical
  order): Alexandre Chartre, Andy Lutomirski, Borislav Petkov, Brian
  Gerst, Frederic Weisbecker, Josh Poimboeuf, Juergen Gross, Lai
  Jiangshan, Macro Elver, Paolo Bonzin,i Paul McKenney, Peter Zijlstra,
  Vitaly Kuznetsov, and Will Deacon"

* tag 'x86-entry-2020-06-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (142 commits)
  x86/entry: Force rcu_irq_enter() when in idle task
  x86/entry: Make NMI use IDTENTRY_RAW
  x86/entry: Treat BUG/WARN as NMI-like entries
  x86/entry: Unbreak __irqentry_text_start/end magic
  x86/entry: __always_inline CR2 for noinstr
  lockdep: __always_inline more for noinstr
  x86/entry: Re-order #DB handler to avoid *SAN instrumentation
  x86/entry: __always_inline arch_atomic_* for noinstr
  x86/entry: __always_inline irqflags for noinstr
  x86/entry: __always_inline debugreg for noinstr
  x86/idt: Consolidate idt functionality
  x86/idt: Cleanup trap_init()
  x86/idt: Use proper constants for table size
  x86/idt: Add comments about early #PF handling
  x86/idt: Mark init only functions __init
  x86/entry: Rename trace_hardirqs_off_prepare()
  x86/entry: Clarify irq_{enter,exit}_rcu()
  x86/entry: Remove DBn stacks
  x86/entry: Remove debug IDT frobbing
  x86/entry: Optimize local_db_save() for virt
  ...
2020-06-13 10:05:47 -07:00
Linus Torvalds
6a45a65888 A set of fixes and updates for x86:
- Unbreak paravirt VDSO clocks. While the VDSO code was moved into lib
     for sharing a subtle check for the validity of paravirt clocks got
     replaced. While the replacement works perfectly fine for bare metal as
     the update of the VDSO clock mode is synchronous, it fails for paravirt
     clocks because the hypervisor can invalidate them asynchronous. Bring
     it back as an optional function so it does not inflict this on
     architectures which are free of PV damage.
 
   - Fix the jiffies to jiffies64 mapping on 64bit so it does not trigger
     an ODR violation on newer compilers
 
   - Three fixes for the SSBD and *IB* speculation mitigation maze to ensure
     consistency, not disabling of some *IB* variants wrongly and to prevent
     a rogue cross process shutdown of SSBD. All marked for stable.
 
   - Add yet more CPU models to the splitlock detection capable list !@#%$!
 
   - Bring the pr_info() back which tells that TSC deadline timer is enabled.
 
   - Reboot quirk for MacBook6,1
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Merge tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull more x86 updates from Thomas Gleixner:
 "A set of fixes and updates for x86:

   - Unbreak paravirt VDSO clocks.

     While the VDSO code was moved into lib for sharing a subtle check
     for the validity of paravirt clocks got replaced. While the
     replacement works perfectly fine for bare metal as the update of
     the VDSO clock mode is synchronous, it fails for paravirt clocks
     because the hypervisor can invalidate them asynchronously.

     Bring it back as an optional function so it does not inflict this
     on architectures which are free of PV damage.

   - Fix the jiffies to jiffies64 mapping on 64bit so it does not
     trigger an ODR violation on newer compilers

   - Three fixes for the SSBD and *IB* speculation mitigation maze to
     ensure consistency, not disabling of some *IB* variants wrongly and
     to prevent a rogue cross process shutdown of SSBD. All marked for
     stable.

   - Add yet more CPU models to the splitlock detection capable list
     !@#%$!

   - Bring the pr_info() back which tells that TSC deadline timer is
     enabled.

   - Reboot quirk for MacBook6,1"

* tag 'x86-urgent-2020-06-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/vdso: Unbreak paravirt VDSO clocks
  lib/vdso: Provide sanity check for cycles (again)
  clocksource: Remove obsolete ifdef
  x86_64: Fix jiffies ODR violation
  x86/speculation: PR_SPEC_FORCE_DISABLE enforcement for indirect branches.
  x86/speculation: Prevent rogue cross-process SSBD shutdown
  x86/speculation: Avoid force-disabling IBPB based on STIBP and enhanced IBRS.
  x86/cpu: Add Sapphire Rapids CPU model number
  x86/split_lock: Add Icelake microserver and Tigerlake CPU models
  x86/apic: Make TSC deadline timer detection message visible
  x86/reboot/quirks: Add MacBook6,1 reboot quirk
2020-06-11 15:54:31 -07:00
Thomas Gleixner
865d3a9afe x86/mce: Address objtools noinstr complaints
Mark the relevant functions noinstr, use the plain non-instrumented MSR
accessors. The only odd part is the instrumentation_begin()/end() pair around the
indirect machine_check_vector() call as objtool can't figure that out. The
possible invoked functions are annotated correctly.

Also use notrace variant of nmi_enter/exit(). If MCEs happen then hardware
latency tracing is the least of the worries.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.476734898@linutronix.de
2020-06-11 15:15:02 +02:00
Thomas Gleixner
c7f3d43b62 clocksource: Remove obsolete ifdef
CONFIG_GENERIC_VDSO_CLOCK_MODE was a transitional config switch which got
removed after all architectures got converted to the new storage model.

But the removal forgot to remove the #ifdef which guards the
vdso_clock_mode sanity check, which effectively disables the sanity check.

Remove it now.

Fixes: f86fd32db7 ("lib/vdso: Cleanup clock mode storage leftovers")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200606221531.845475036@linutronix.de
2020-06-09 16:36:47 +02:00
Linus Torvalds
9ff7258575 Merge branch 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull proc updates from Eric Biederman:
 "This has four sets of changes:

   - modernize proc to support multiple private instances

   - ensure we see the exit of each process tid exactly

   - remove has_group_leader_pid

   - use pids not tasks in posix-cpu-timers lookup

  Alexey updated proc so each mount of proc uses a new superblock. This
  allows people to actually use mount options with proc with no fear of
  messing up another mount of proc. Given the kernel's internal mounts
  of proc for things like uml this was a real problem, and resulted in
  Android's hidepid mount options being ignored and introducing security
  issues.

  The rest of the changes are small cleanups and fixes that came out of
  my work to allow this change to proc. In essence it is swapping the
  pids in de_thread during exec which removes a special case the code
  had to handle. Then updating the code to stop handling that special
  case"

* 'proc-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  proc: proc_pid_ns takes super_block as an argument
  remove the no longer needed pid_alive() check in __task_pid_nr_ns()
  posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock
  posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type
  posix-cpu-timers: Extend rcu_read_lock removing task_struct references
  signal: Remove has_group_leader_pid
  exec: Remove BUG_ON(has_group_leader_pid)
  posix-cpu-timer:  Unify the now redundant code in lookup_task
  posix-cpu-timer: Tidy up group_leader logic in lookup_task
  proc: Ensure we see the exit of each process tid exactly once
  rculist: Add hlists_swap_heads_rcu
  proc: Use PIDTYPE_TGID in next_tgid
  Use proc_pid_ns() to get pid_namespace from the proc superblock
  proc: use named enums for better readability
  proc: use human-readable values for hidepid
  docs: proc: add documentation for "hidepid=4" and "subset=pid" options and new mount behavior
  proc: add option to mount only a pids subset
  proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option
  proc: allow to mount many instances of proc in one pid namespace
  proc: rename struct proc_fs_info to proc_fs_opts
2020-06-04 13:54:34 -07:00
Linus Torvalds
cb8e59cc87 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from David Miller:

 1) Allow setting bluetooth L2CAP modes via socket option, from Luiz
    Augusto von Dentz.

 2) Add GSO partial support to igc, from Sasha Neftin.

 3) Several cleanups and improvements to r8169 from Heiner Kallweit.

 4) Add IF_OPER_TESTING link state and use it when ethtool triggers a
    device self-test. From Andrew Lunn.

 5) Start moving away from custom driver versions, use the globally
    defined kernel version instead, from Leon Romanovsky.

 6) Support GRO vis gro_cells in DSA layer, from Alexander Lobakin.

 7) Allow hard IRQ deferral during NAPI, from Eric Dumazet.

 8) Add sriov and vf support to hinic, from Luo bin.

 9) Support Media Redundancy Protocol (MRP) in the bridging code, from
    Horatiu Vultur.

10) Support netmap in the nft_nat code, from Pablo Neira Ayuso.

11) Allow UDPv6 encapsulation of ESP in the ipsec code, from Sabrina
    Dubroca. Also add ipv6 support for espintcp.

12) Lots of ReST conversions of the networking documentation, from Mauro
    Carvalho Chehab.

13) Support configuration of ethtool rxnfc flows in bcmgenet driver,
    from Doug Berger.

14) Allow to dump cgroup id and filter by it in inet_diag code, from
    Dmitry Yakunin.

15) Add infrastructure to export netlink attribute policies to
    userspace, from Johannes Berg.

16) Several optimizations to sch_fq scheduler, from Eric Dumazet.

17) Fallback to the default qdisc if qdisc init fails because otherwise
    a packet scheduler init failure will make a device inoperative. From
    Jesper Dangaard Brouer.

18) Several RISCV bpf jit optimizations, from Luke Nelson.

19) Correct the return type of the ->ndo_start_xmit() method in several
    drivers, it's netdev_tx_t but many drivers were using
    'int'. From Yunjian Wang.

20) Add an ethtool interface for PHY master/slave config, from Oleksij
    Rempel.

21) Add BPF iterators, from Yonghang Song.

22) Add cable test infrastructure, including ethool interfaces, from
    Andrew Lunn. Marvell PHY driver is the first to support this
    facility.

23) Remove zero-length arrays all over, from Gustavo A. R. Silva.

24) Calculate and maintain an explicit frame size in XDP, from Jesper
    Dangaard Brouer.

25) Add CAP_BPF, from Alexei Starovoitov.

26) Support terse dumps in the packet scheduler, from Vlad Buslov.

27) Support XDP_TX bulking in dpaa2 driver, from Ioana Ciornei.

28) Add devm_register_netdev(), from Bartosz Golaszewski.

29) Minimize qdisc resets, from Cong Wang.

30) Get rid of kernel_getsockopt and kernel_setsockopt in order to
    eliminate set_fs/get_fs calls. From Christoph Hellwig.

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2517 commits)
  selftests: net: ip_defrag: ignore EPERM
  net_failover: fixed rollback in net_failover_open()
  Revert "tipc: Fix potential tipc_aead refcnt leak in tipc_crypto_rcv"
  Revert "tipc: Fix potential tipc_node refcnt leak in tipc_rcv"
  vmxnet3: allow rx flow hash ops only when rss is enabled
  hinic: add set_channels ethtool_ops support
  selftests/bpf: Add a default $(CXX) value
  tools/bpf: Don't use $(COMPILE.c)
  bpf, selftests: Use bpf_probe_read_kernel
  s390/bpf: Use bcr 0,%0 as tail call nop filler
  s390/bpf: Maintain 8-byte stack alignment
  selftests/bpf: Fix verifier test
  selftests/bpf: Fix sample_cnt shared between two threads
  bpf, selftests: Adapt cls_redirect to call csum_level helper
  bpf: Add csum_level helper for fixing up csum levels
  bpf: Fix up bpf_skb_adjust_room helper's skb csum setting
  sfc: add missing annotation for efx_ef10_try_update_nic_stats_vf()
  crypto/chtls: IPv6 support for inline TLS
  Crypto/chcr: Fixes a coccinile check error
  Crypto/chcr: Fixes compilations warnings
  ...
2020-06-03 16:27:18 -07:00
Christian Brauner
f2a8d52e0a
nsproxy: add struct nsset
Add a simple struct nsset. It holds all necessary pieces to switch to a new
set of namespaces without leaving a task in a half-switched state which we
will make use of in the next patch. This patch switches the existing setns
logic over without causing a change in setns() behavior. This brings
setns() closer to how unshare() works(). The prepare_ns() function is
responsible to prepare all necessary information. This has two reasons.
First it minimizes dependencies between individual namespaces, i.e. all
install handler can expect that all fields are properly initialized
independent in what order they are called in. Second, this makes the code
easier to maintain and easier to follow if it needs to be changed.

The prepare_ns() helper will only be switched over to use a flags argument
in the next patch. Here it will still use nstype as a simple integer
argument which was argued would be clearer. I'm not particularly
opinionated about this if it really helps or not. The struct nsset itself
already contains the flags field since its name already indicates that it
can contain information required by different namespaces. None of this
should have functional consequences.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Jann Horn <jannh@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Link: https://lore.kernel.org/r/20200505140432.181565-2-christian.brauner@ubuntu.com
2020-05-09 13:57:12 +02:00
Eric W. Biederman
964987738b posix-cpu-timers: Replace __get_task_for_clock with pid_for_clock
Now that the codes store references to pids instead of referendes to
tasks.  Looking up a task for a clock instead of looking up a struct
pid makes the code more difficult to verify it is correct than
necessary.

In posix_cpu_timers_create get_task_pid can race with release_task for
threads and return a NULL pid.  As put_pid and cpu_timer_task_rcu
handle NULL pids just fine the code works without problems but it is
an extra case to consider and keep in mind while verifying and
modifying the code.

There are races with de_thread to consider that only don't apply
because thread clocks are only allowed for threads in the same
thread_group.

So instead of leaving a burden for people making modification to the
code in the future return a rcu protected struct pid for the clock
instead.

The logic for __get_task_for_pid and lookup_task has been folded into
the new function pid_for_clock with the only change being the logic
has been modified from working on a task to working on a pid that
will be returned.

In posix_cpu_clock_get instead of calling pid_for_clock checking the
result and then calling pid_task to get the task.  The result of
pid_for_clock is fed directly into pid_task.  This is safe because
pid_task handles NULL pids.  As such an extra error check was
unnecessary.

Instead of hiding the flag that enables the special clock_gettime
handling, I have made the 3 callers just pass the flag in themselves.
That is less code and seems just as simple to work with as the
wrapper functions.

Historically the clock_gettime special case of allowing a process
clock to be found by the thread id did not even exist [33ab0fec33]
but Thomas Gleixner reports that he has found code that uses that
functionality [55e8c8eb2c].

Link: https://lkml.kernel.org/r/87zhaxqkwa.fsf@nanos.tec.linutronix.de/
Ref: 33ab0fec33 ("posix-timers: Consolidate posix_cpu_clock_get()")
Ref: 55e8c8eb2c ("posix-cpu-timers: Store a reference to a pid not a task")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-04-29 08:14:41 -05:00
Eric W. Biederman
fece98260f posix-cpu-timers: Replace cpu_timer_pid_type with clock_pid_type
Taking a clock and returning a pid_type is a more general and
a superset of taking a timer and returning a pid_type.

Perform this generalization so that future changes may use
this code on clocks as well as timers.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-04-29 07:14:51 -05:00
Eric W. Biederman
9bf7c32409 posix-cpu-timers: Extend rcu_read_lock removing task_struct references
Now that the code stores of pid references it is no longer necessary
or desirable to take a reference on task_struct in __get_task_for_clock.

Instead extend the scope of rcu_read_lock and remove the reference
counting on struct task_struct entirely.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-04-29 07:14:12 -05:00
Eric W. Biederman
c7f5194054 posix-cpu-timer: Unify the now redundant code in lookup_task
Now that both !thread paths through lookup_task call
thread_group_leader, unify them into the single test at the end of
lookup_task.

This unification just makes it clear what is happening in the gettime
special case of lookup_task.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-04-28 16:46:04 -05:00
Eric W. Biederman
8feebc6713 posix-cpu-timer: Tidy up group_leader logic in lookup_task
Replace has_group_leader_pid with thread_group_leader.  Years ago Oleg
suggested changing thread_group_leader to has_group_leader_pid to handle
races.  Looking at the code then and now I don't see how it ever helped.
Especially as then the code really did need to be the
thread_group_leader.

Today it doesn't make a difference if thread_group_leader races with
de_thread as the task returned from lookup_task in the non-thread case is
just used to find values in task->signal.

Since the races with de_thread have never been handled revert
has_group_header_pid to thread_group_leader for clarity.

Update the comment in lookup_task to remove implementation details that
are no longer true and to mention task->signal instead of task->sighand,
as the relevant cpu timer details are all in task->signal.

Ref: 55e8c8eb2c ("posix-cpu-timers: Store a reference to a pid not a task")
Ref: c0deae8c95 ("posix-cpu-timers: Rcu_read_lock/unlock protect find_task_by_vpid call")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2020-04-28 16:42:03 -05:00
Daniel Borkmann
0b54142e4b Merge branch 'work.sysctl' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull in Christoph Hellwig's series that changes the sysctl's ->proc_handler
methods to take kernel pointers instead. It gets rid of the set_fs address
space overrides used by BPF. As per discussion, pull in the feature branch
into bpf-next as it relates to BPF sysctl progs.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200427071508.GV23230@ZenIV.linux.org.uk/T/
2020-04-28 21:23:38 +02:00
Christoph Hellwig
32927393dc sysctl: pass kernel pointers to ->proc_handler
Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2020-04-27 02:07:40 -04:00
Andrei Vagin
94d440d618 proc, time/namespace: Show clock symbolic names in /proc/pid/timens_offsets
Michael Kerrisk suggested to replace numeric clock IDs with symbolic names.

Now the content of these files looks like this:
$ cat /proc/774/timens_offsets
monotonic      864000         0
boottime      1728000         0

For setting offsets, both representations of clocks (numeric and symbolic)
can be used.

As for compatibility, it is acceptable to change things as long as
userspace doesn't care. The format of timens_offsets files is very new and
there are no userspace tools yet which rely on this format.

But three projects crun, util-linux and criu rely on the interface of
setting time offsets and this is why it's required to continue supporting
the numeric clock IDs on write.

Fixes: 04a8682a71 ("fs/proc: Introduce /proc/pid/timens_offsets")
Suggested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20200411154031.642557-1-avagin@gmail.com
2020-04-16 12:10:54 +02:00
Michael Kerrisk (man-pages)
b801f1e22c time/namespace: Fix time_for_children symlink
Looking at the contents of the /proc/PID/ns/time_for_children symlink shows
an anomaly:

$ ls -l /proc/self/ns/* |awk '{print $9, $10, $11}'
...
/proc/self/ns/pid -> pid:[4026531836]
/proc/self/ns/pid_for_children -> pid:[4026531836]
/proc/self/ns/time -> time:[4026531834]
/proc/self/ns/time_for_children -> time_for_children:[4026531834]
/proc/self/ns/user -> user:[4026531837]
...

The reference for 'time_for_children' should be a 'time' namespace, just as
the reference for 'pid_for_children' is a 'pid' namespace.  In other words,
the above time_for_children link should read:

/proc/self/ns/time_for_children -> time:[4026531834]

Fixes: 769071ac9f ("ns: Introduce Time Namespace")
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: Andrei Vagin <avagin@gmail.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/a2418c48-ed80-3afe-116e-6611cb799557@gmail.com
2020-04-07 12:37:21 +02:00
Sebastian Andrzej Siewior
73d20564e0 hrtimer: Don't dereference the hrtimer pointer after the callback
A hrtimer can be released in its callback, but lockdep_hrtimer_exit()
dereferences the pointer after the callback returns, i.e. a potential use
after free.

Retrieve the context in which the hrtimer expires before the callback is
invoked and use it in lockdep_hrtimer_exit().

Fixes: 40db173965 ("lockdep: Add hrtimer context tracing bits")
Reported-by: syzbot+62c155c276e580cfb606@syzkaller.appspotmail.com
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200331201849.fkp2siy3vcdqvqlz@linutronix.de
2020-04-01 13:20:14 +02:00
Linus Torvalds
dbb381b619 timekeeping and timer updates:
Core:
 
   - Consolidation of the vDSO build infrastructure to address the
     difficulties of cross-builds for ARM64 compat vDSO libraries by
     restricting the exposure of header content to the vDSO build.
 
     This is achieved by splitting out header content into separate
     headers. which contain only the minimaly required information which is
     necessary to build the vDSO. These new headers are included from the
     kernel headers and the vDSO specific files.
 
   - Enhancements to the generic vDSO library allowing more fine grained
     control over the compiled in code, further reducing architecture
     specific storage and preparing for adopting the generic library by PPC.
 
   - Cleanup and consolidation of the exit related code in posix CPU timers.
 
   - Small cleanups and enhancements here and there
 
  Drivers:
 
   - The obligatory new drivers: Ingenic JZ47xx and X1000 TCU support
 
   - Correct the clock rate of PIT64b global clock
 
   - setup_irq() cleanup
 
   - Preparation for PWM and suspend support for the TI DM timer
 
   - Expand the fttmr010 driver to support ast2600 systems
 
   - The usual small fixes, enhancements and cleanups all over the place
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Merge tag 'timers-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timekeeping and timer updates from Thomas Gleixner:
 "Core:

   - Consolidation of the vDSO build infrastructure to address the
     difficulties of cross-builds for ARM64 compat vDSO libraries by
     restricting the exposure of header content to the vDSO build.

     This is achieved by splitting out header content into separate
     headers. which contain only the minimaly required information which
     is necessary to build the vDSO. These new headers are included from
     the kernel headers and the vDSO specific files.

   - Enhancements to the generic vDSO library allowing more fine grained
     control over the compiled in code, further reducing architecture
     specific storage and preparing for adopting the generic library by
     PPC.

   - Cleanup and consolidation of the exit related code in posix CPU
     timers.

   - Small cleanups and enhancements here and there

  Drivers:

   - The obligatory new drivers: Ingenic JZ47xx and X1000 TCU support

   - Correct the clock rate of PIT64b global clock

   - setup_irq() cleanup

   - Preparation for PWM and suspend support for the TI DM timer

   - Expand the fttmr010 driver to support ast2600 systems

   - The usual small fixes, enhancements and cleanups all over the
     place"

* tag 'timers-core-2020-03-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
  Revert "clocksource/drivers/timer-probe: Avoid creating dead devices"
  vdso: Fix clocksource.h macro detection
  um: Fix header inclusion
  arm64: vdso32: Enable Clang Compilation
  lib/vdso: Enable common headers
  arm: vdso: Enable arm to use common headers
  x86/vdso: Enable x86 to use common headers
  mips: vdso: Enable mips to use common headers
  arm64: vdso32: Include common headers in the vdso library
  arm64: vdso: Include common headers in the vdso library
  arm64: Introduce asm/vdso/processor.h
  arm64: vdso32: Code clean up
  linux/elfnote.h: Replace elf.h with UAPI equivalent
  scripts: Fix the inclusion order in modpost
  common: Introduce processor.h
  linux/ktime.h: Extract common header for vDSO
  linux/jiffies.h: Extract common header for vDSO
  linux/time64.h: Extract common header for vDSO
  linux/time32.h: Extract common header for vDSO
  linux/time.h: Extract common header for vDSO
  ...
2020-03-30 18:51:47 -07:00
Linus Torvalds
4b9fd8a829 Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Continued user-access cleanups in the futex code.

   - percpu-rwsem rewrite that uses its own waitqueue and atomic_t
     instead of an embedded rwsem. This addresses a couple of
     weaknesses, but the primary motivation was complications on the -rt
     kernel.

   - Introduce raw lock nesting detection on lockdep
     (CONFIG_PROVE_RAW_LOCK_NESTING=y), document the raw_lock vs. normal
     lock differences. This too originates from -rt.

   - Reuse lockdep zapped chain_hlocks entries, to conserve RAM
     footprint on distro-ish kernels running into the "BUG:
     MAX_LOCKDEP_CHAIN_HLOCKS too low!" depletion of the lockdep
     chain-entries pool.

   - Misc cleanups, smaller fixes and enhancements - see the changelog
     for details"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (55 commits)
  fs/buffer: Make BH_Uptodate_Lock bit_spin_lock a regular spinlock_t
  thermal/x86_pkg_temp: Make pkg_temp_lock a raw_spinlock_t
  Documentation/locking/locktypes: Minor copy editor fixes
  Documentation/locking/locktypes: Further clarifications and wordsmithing
  m68knommu: Remove mm.h include from uaccess_no.h
  x86: get rid of user_atomic_cmpxchg_inatomic()
  generic arch_futex_atomic_op_inuser() doesn't need access_ok()
  x86: don't reload after cmpxchg in unsafe_atomic_op2() loop
  x86: convert arch_futex_atomic_op_inuser() to user_access_begin/user_access_end()
  objtool: whitelist __sanitizer_cov_trace_switch()
  [parisc, s390, sparc64] no need for access_ok() in futex handling
  sh: no need of access_ok() in arch_futex_atomic_op_inuser()
  futex: arch_futex_atomic_op_inuser() calling conventions change
  completion: Use lockdep_assert_RT_in_threaded_ctx() in complete_all()
  lockdep: Add posixtimer context tracing bits
  lockdep: Annotate irq_work
  lockdep: Add hrtimer context tracing bits
  lockdep: Introduce wait-type checks
  completion: Use simple wait queues
  sched/swait: Prepare usage in completions
  ...
2020-03-30 16:17:15 -07:00
Ingo Molnar
baf5fe7618 Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull RCU changes from Paul E. McKenney:

 - Make kfree_rcu() use kfree_bulk() for added performance
 - RCU updates
 - Callback-overload handling updates
 - Tasks-RCU KCSAN and sparse updates
 - Locking torture test and RCU torture test updates
 - Documentation updates
 - Miscellaneous fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-24 10:10:09 +01:00
Sebastian Andrzej Siewior
d53f2b62fc lockdep: Add posixtimer context tracing bits
Splitting run_posix_cpu_timers() into two parts is work in progress which
is stuck on other entry code related problems. The heavy lifting which
involves locking of sighand lock will be moved into task context so the
necessary execution time is burdened on the task and not on interrupt
context.

Until this work completes lockdep with the spinlock nesting rules enabled
would emit warnings for this known context.

Prevent it by setting "->irq_config = 1" for the invocation of
run_posix_cpu_timers() so lockdep does not complain when sighand lock is
acquried. This will be removed once the split is completed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.751182723@linutronix.de
2020-03-21 16:00:25 +01:00
Sebastian Andrzej Siewior
49915ac35c lockdep: Annotate irq_work
Mark irq_work items with IRQ_WORK_HARD_IRQ which should be invoked in
hardirq context even on PREEMPT_RT. IRQ_WORK without this flag will be
invoked in softirq context on PREEMPT_RT.

Set ->irq_config to 1 for the IRQ_WORK items which are invoked in softirq
context so lockdep knows that these can safely acquire a spinlock_t.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.643576700@linutronix.de
2020-03-21 16:00:24 +01:00
Sebastian Andrzej Siewior
40db173965 lockdep: Add hrtimer context tracing bits
Set current->irq_config = 1 for hrtimers which are not marked to expire in
hard interrupt context during hrtimer_init(). These timers will expire in
softirq context on PREEMPT_RT.

Setting this allows lockdep to differentiate these timers. If a timer is
marked to expire in hard interrupt context then the timer callback is not
supposed to acquire a regular spinlock instead of a raw_spinlock in the
expiry callback.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.534508206@linutronix.de
2020-03-21 16:00:24 +01:00
Thomas Gleixner
e5d4d1756b timekeeping: Split jiffies seqlock
seqlock consists of a sequence counter and a spinlock_t which is used to
serialize the writers. spinlock_t is substituted by a "sleeping" spinlock
on PREEMPT_RT enabled kernels which breaks the usage in the timekeeping
code as the writers are executed in hard interrupt and therefore
non-preemptible context even on PREEMPT_RT.

The spinlock in seqlock cannot be unconditionally replaced by a
raw_spinlock_t as many seqlock users have nesting spinlock sections or
other code which is not suitable to run in truly atomic context on RT.

Instead of providing a raw_seqlock API for a single use case, open code the
seqlock for the jiffies use case and implement it with a raw_spinlock_t and
a sequence counter.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200321113242.120587764@linutronix.de
2020-03-21 16:00:23 +01:00
Thomas Gleixner
52da479a9a Revert "tick/common: Make tick_periodic() check for missing ticks"
This reverts commit d441dceb5d due to
boot failures.

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
2020-03-19 19:47:48 +01:00
Ahmed S. Darwish
2c8bd58812 time/sched_clock: Expire timer in hardirq context
To minimize latency, PREEMPT_RT kernels expires hrtimers in preemptible
softirq context by default. This can be overriden by marking the timer's
expiry with HRTIMER_MODE_HARD.

sched_clock_timer is missing this annotation: if its callback is preempted
and the duration of the preemption exceeds the wrap around time of the
underlying clocksource, sched clock will get out of sync.

Mark the sched_clock_timer for expiry in hard interrupt context.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200309181529.26558-1-a.darwish@linutronix.de
2020-03-19 09:45:08 +01:00
Waiman Long
d441dceb5d tick/common: Make tick_periodic() check for missing ticks
The tick_periodic() function is used at the beginning part of the
bootup process for time keeping while the other clock sources are
being initialized.

The current code assumes that all the timer interrupts are handled in
a timely manner with no missing ticks. That is not actually true. Some
ticks are missed and there are some discrepancies between the tick time
(jiffies) and the timestamp reported in the kernel log.  Some systems,
however, are more prone to missing ticks than the others.  In the extreme
case, the discrepancy can actually cause a soft lockup message to be
printed by the watchdog kthread. For example, on a Cavium ThunderX2
Sabre arm64 system:

 [   25.496379] watchdog: BUG: soft lockup - CPU#14 stuck for 22s!

On that system, the missing ticks are especially prevalent during the
smp_init() phase of the boot process. With an instrumented kernel,
it was found that it took about 24s as reported by the timestamp for
the tick to accumulate 4s of time.

Investigation and bisection done by others seemed to point to the
commit 73f3816609 ("arm64: Advertise mitigation of Spectre-v2, or
lack thereof") as the culprit. It could also be a firmware issue as
new firmware was promised that would fix the issue.

To properly address this problem, stop assuming that there will be no
missing tick in tick_periodic(). Modify it to follow the example of
tick_do_update_jiffies64() by using another reference clock to check for
missing ticks. Since the watchdog timer uses running_clock(), it is used
here as the reference. With this applied, the soft lockup problem in the
affected arm64 system is gone and tick time tracks much more closely to the
timestamp time.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200207193929.27308-1-longman@redhat.com
2020-03-04 10:18:11 +01:00
Wen Yang
38f7b0b131 hrtimer: Cast explicitely to u32t in __ktime_divns()
do_div() does a 64-by-32 division at least on 32bit platforms, while the
divisor 'div' is explicitly casted to unsigned long, thus 64-bit on 64-bit
platforms.

The code already ensures that the divisor is less than 2^32. Hence the
proper cast type is u32.

Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200130130851.29204-1-wenyang@linux.alibaba.com
2020-03-04 10:17:51 +01:00
Wen Yang
4cbbc3a0ee timekeeping: Prevent 32bit truncation in scale64_check_overflow()
While unlikely the divisor in scale64_check_overflow() could be >= 32bit in
scale64_check_overflow(). do_div() truncates the divisor to 32bit at least
on 32bit platforms.

Use div64_u64() instead to avoid the truncation to 32-bit.

[ tglx: Massaged changelog ]

Signed-off-by: Wen Yang <wenyang@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200120100523.45656-1-wenyang@linux.alibaba.com
2020-03-04 10:17:51 +01:00
Eric W. Biederman
55e8c8eb2c posix-cpu-timers: Store a reference to a pid not a task
posix cpu timers do not handle the death of a process well.

This is most clearly seen when a multi-threaded process calls exec from a
thread that is not the leader of the thread group.  The posix cpu timer code
continues to pin the old thread group leader and is unable to find the
siglock from there.

This results in posix_cpu_timer_del being unable to delete a timer,
posix_cpu_timer_set being unable to set a timer.  Further to compensate for
the problems in posix_cpu_timer_del on a multi-threaded exec all timers
that point at the multi-threaded task are stopped.

The code for the timers fundamentally needs to check if the target
process/thread is alive.  This needs an extra level of indirection. This
level of indirection is already available in struct pid.

So replace cpu.task with cpu.pid to get the needed extra layer of
indirection.

In addition to handling things more cleanly this reduces the amount of
memory a timer can pin when a process exits and then is reaped from
a task_struct to the vastly smaller struct pid.

Fixes: e0a7021710 ("posix-cpu-timers: workaround to suppress the problems with mt exec")
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87wo86tz6d.fsf@x220.int.ebiederm.org
2020-03-04 09:54:55 +01:00
Eric W. Biederman
beb41d9cbe posix-cpu-timers: Pass the task into arm_timer()
The task has been already computed to take siglock before calling
arm_timer. So pass the benefit of that labor into arm_timer().

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/8736auvdt1.fsf@x220.int.ebiederm.org
2020-03-01 11:21:44 +01:00
Eric W. Biederman
60f2ceaa81 posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group
As of e78c349679 ("time, signal: Protect resource use statistics
with seqlock") cpu_clock_sample_group no longers needs siglock
protection.  Unfortunately no one realized it at the time.

Remove the extra locking that is for cpu_clock_sample_group and not
for cpu_clock_sample.  This significantly simplifies the code.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/878skmvdts.fsf@x220.int.ebiederm.org
2020-03-01 11:21:44 +01:00
Eric W. Biederman
a2efdbf4fc posix-cpu-timers: cpu_clock_sample_group() no longer needs siglock
As of e78c349679 ("time, signal: Protect resource use statistics with
seqlock") cpu_clock_sample_group() no longer needs siglock protection so
remove the stale comment.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87eeuevduq.fsf@x220.int.ebiederm.org
2020-03-01 11:21:43 +01:00
Arnd Bergmann
412c53a680 y2038: remove unused time32 interfaces
No users remain, so kill these off before we grow new ones.

Link: http://lkml.kernel.org/r/20200110154232.4104492-3-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-02-21 11:22:15 -08:00
Eric Dumazet
90c018942c timer: Use hlist_unhashed_lockless() in timer_pending()
The timer_pending() function is mostly used in lockless contexts, so
Without proper annotations, KCSAN might detect a data-race [1].

Using hlist_unhashed_lockless() instead of hand-coding it seems
appropriate (as suggested by Paul E. McKenney).

[1]

BUG: KCSAN: data-race in del_timer / detach_if_pending

write to 0xffff88808697d870 of 8 bytes by task 10 on cpu 0:
 __hlist_del include/linux/list.h:764 [inline]
 detach_timer kernel/time/timer.c:815 [inline]
 detach_if_pending+0xcd/0x2d0 kernel/time/timer.c:832
 try_to_del_timer_sync+0x60/0xb0 kernel/time/timer.c:1226
 del_timer_sync+0x6b/0xa0 kernel/time/timer.c:1365
 schedule_timeout+0x2d2/0x6e0 kernel/time/timer.c:1896
 rcu_gp_fqs_loop+0x37c/0x580 kernel/rcu/tree.c:1639
 rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff88808697d870 of 8 bytes by task 12060 on cpu 1:
 del_timer+0x3b/0xb0 kernel/time/timer.c:1198
 sk_stop_timer+0x25/0x60 net/core/sock.c:2845
 inet_csk_clear_xmit_timers+0x69/0xa0 net/ipv4/inet_connection_sock.c:523
 tcp_clear_xmit_timers include/net/tcp.h:606 [inline]
 tcp_v4_destroy_sock+0xa3/0x3f0 net/ipv4/tcp_ipv4.c:2096
 inet_csk_destroy_sock+0xf4/0x250 net/ipv4/inet_connection_sock.c:836
 tcp_close+0x6f3/0x970 net/ipv4/tcp.c:2497
 inet_release+0x86/0x100 net/ipv4/af_inet.c:427
 __sock_release+0x85/0x160 net/socket.c:590
 sock_close+0x24/0x30 net/socket.c:1268
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:163

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12060 Comm: syz-executor.5 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine,

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ paulmck: Pulled in Eric's later amendments. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-02-20 15:58:22 -08:00
Amol Grover
5fb1c2a5bb posix-timers: Pass lockdep expression to RCU lists
head is traversed using hlist_for_each_entry_rcu outside an RCU read-side
critical section but under the protection of hash_lock.

Hence, add corresponding lockdep expression to silence false-positive
lockdep warnings, and harden RCU lists.

[ tglx: Removed the macro and put the condition right where it's used ]

Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200216074330.GA14025@workstation-portable
2020-02-17 20:12:19 +01:00
Alexander Popov
6e317c32fd timer: Improve the comment describing schedule_timeout()
When working commit 6dcd5d7a7a, a mistake was noticed by Linus:
schedule_timeout() was called without setting the task state to anything
particular.

It calls the scheduler, but doesn't delay anything, because the task stays
runnable. That happens because sched_submit_work() does nothing for tasks
in TASK_RUNNING state.

That turned out to be the intended behavior. Adding a WARN() is not useful
as the task could be woken up right after setting the state and before
reaching schedule_timeout().

Improve the comment about schedule_timeout() and describe that more
explicitly.

Signed-off-by: Alexander Popov <alex.popov@linux.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200117225900.16340-1-alex.popov@linux.com
2020-02-17 20:12:19 +01:00
Thomas Gleixner
2d6b01bd88 lib/vdso: Move VCLOCK_TIMENS to vdso_clock_modes
Move the time namespace indicator clock mode to the other ones for
consistency sake.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200207124403.656097274@linutronix.de
2020-02-17 20:12:17 +01:00
Thomas Gleixner
c7a18100bd lib/vdso: Avoid highres update if clocksource is not VDSO capable
If the current clocksource is not VDSO capable there is no point in
updating the high resolution parts of the VDSO data.

Replace the architecture specific check with a check for a VDSO capable
clocksource and skip the update if there is none.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200207124403.563379423@linutronix.de
2020-02-17 20:12:17 +01:00
Thomas Gleixner
f86fd32db7 lib/vdso: Cleanup clock mode storage leftovers
Now that all architectures are converted to use the generic storage the
helpers and conditionals can be removed.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200207124403.470699892@linutronix.de
2020-02-17 20:12:17 +01:00
Thomas Gleixner
5d51bee725 clocksource: Add common vdso clock mode storage
All architectures which use the generic VDSO code have their own storage
for the VDSO clock mode. That's pointless and just requires duplicate code.

Provide generic storage for it. The new Kconfig symbol is intermediate and
will be removed once all architectures are converted over.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lkml.kernel.org/r/20200207124403.028046322@linutronix.de
2020-02-17 14:40:23 +01:00
Linus Torvalds
2fbc23c738 Two small fixes for the time(r) subsystem:
- Handle a subtle race between the clocksource watchdog and a concurrent
     clocksource watchdog stop/start sequence correctly to prevent a timer
     double add bug.
 
   - Fix the file path for the core time namespace file.
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Merge tag 'timers-urgent-2020-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "Two small fixes for the time(r) subsystem:

   - Handle a subtle race between the clocksource watchdog and a
     concurrent clocksource watchdog stop/start sequence correctly to
     prevent a timer double add bug.

   - Fix the file path for the core time namespace file"

* tag 'timers-urgent-2020-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource: Prevent double add_timer_on() for watchdog_timer
  MAINTAINERS: Correct path to time namespace source file
2020-02-09 12:00:12 -08:00
Konstantin Khlebnikov
febac332a8 clocksource: Prevent double add_timer_on() for watchdog_timer
Kernel crashes inside QEMU/KVM are observed:

  kernel BUG at kernel/time/timer.c:1154!
  BUG_ON(timer_pending(timer) || !timer->function) in add_timer_on().

At the same time another cpu got:

  general protection fault: 0000 [#1] SMP PTI of poinson pointer 0xdead000000000200 in:

  __hlist_del at include/linux/list.h:681
  (inlined by) detach_timer at kernel/time/timer.c:818
  (inlined by) expire_timers at kernel/time/timer.c:1355
  (inlined by) __run_timers at kernel/time/timer.c:1686
  (inlined by) run_timer_softirq at kernel/time/timer.c:1699

Unfortunately kernel logs are badly scrambled, stacktraces are lost.

Printing the timer->function before the BUG_ON() pointed to
clocksource_watchdog().

The execution of clocksource_watchdog() can race with a sequence of
clocksource_stop_watchdog() .. clocksource_start_watchdog():

expire_timers()
 detach_timer(timer, true);
  timer->entry.pprev = NULL;
 raw_spin_unlock_irq(&base->lock);
 call_timer_fn
  clocksource_watchdog()

					clocksource_watchdog_kthread() or
					clocksource_unbind()

					spin_lock_irqsave(&watchdog_lock, flags);
					clocksource_stop_watchdog();
					 del_timer(&watchdog_timer);
					 watchdog_running = 0;
					spin_unlock_irqrestore(&watchdog_lock, flags);

					spin_lock_irqsave(&watchdog_lock, flags);
					clocksource_start_watchdog();
					 add_timer_on(&watchdog_timer, ...);
					 watchdog_running = 1;
					spin_unlock_irqrestore(&watchdog_lock, flags);

  spin_lock(&watchdog_lock);
  add_timer_on(&watchdog_timer, ...);
   BUG_ON(timer_pending(timer) || !timer->function);
    timer_pending() -> true
    BUG()

I.e. inside clocksource_watchdog() watchdog_timer could be already armed.

Check timer_pending() before calling add_timer_on(). This is sufficient as
all operations are synchronized by watchdog_lock.

Fixes: 75c5158f70 ("timekeeping: Update clocksource with stop_machine")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/158048693917.4378.13823603769948933793.stgit@buzz
2020-02-01 11:07:56 +01:00
Linus Torvalds
22b17db4ea y2038: core, driver and file system changes
These are updates to device drivers and file systems that for some reason
 or another were not included in the kernel in the previous y2038 series.
 
 I've gone through all users of time_t again to make sure the kernel is
 in a long-term maintainable state, replacing all remaining references
 to time_t with safe alternatives.
 
 Some related parts of the series were picked up into the nfsd, xfs,
 alsa and v4l2 trees. A final set of patches in linux-mm removes the now
 unused time_t/timeval/timespec types and helper functions after all five
 branches are merged for linux-5.6, ensuring that no new users get merged.
 
 As a result, linux-5.6, or my backport of the patches to 5.4 [1], should
 be the first release that can serve as a base for a 32-bit system designed
 to run beyond year 2038, with a few remaining caveats:
 
 - All user space must be compiled with a 64-bit time_t, which will be
   supported in the coming musl-1.2 and glibc-2.32 releases, along with
   installed kernel headers from linux-5.6 or higher.
 
 - Applications that use the system call interfaces directly need to be
   ported to use the time64 syscalls added in linux-5.1 in place of the
   existing system calls. This impacts most users of futex() and seccomp()
   as well as programming languages that have their own runtime environment
   not based on libc.
 
 - Applications that use a private copy of kernel uapi header files or
   their contents may need to update to the linux-5.6 version, in
   particular for sound/asound.h, xfs/xfs_fs.h, linux/input.h,
   linux/elfcore.h, linux/sockios.h, linux/timex.h and linux/can/bcm.h.
 
 - A few remaining interfaces cannot be changed to pass a 64-bit time_t
   in a compatible way, so they must be configured to use CLOCK_MONOTONIC
   times or (with a y2106 problem) unsigned 32-bit timestamps. Most
   importantly this impacts all users of 'struct input_event'.
 
 - All y2038 problems that are present on 64-bit machines also apply to
   32-bit machines. In particular this affects file systems with on-disk
   timestamps using signed 32-bit seconds: ext4 with ext3-style small
   inodes, ext2, xfs (to be fixed soon) and ufs.
 
 Changes since v1 [2]:
 
 - Add Acks I received
 - Rebase to v5.5-rc1, dropping patches that got merged already
 - Add NFS, XFS and the final three patches from another series
 - Rewrite etnaviv patches
 - Add one late revert to avoid an etnaviv regression
 
 [1] https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/log/?h=y2038-endgame
 [2] https://lore.kernel.org/lkml/20191108213257.3097633-1-arnd@arndb.de/
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Merge tag 'y2038-drivers-for-v5.6-signed' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground

Pull y2038 updates from Arnd Bergmann:
 "Core, driver and file system changes

  These are updates to device drivers and file systems that for some
  reason or another were not included in the kernel in the previous
  y2038 series.

  I've gone through all users of time_t again to make sure the kernel is
  in a long-term maintainable state, replacing all remaining references
  to time_t with safe alternatives.

  Some related parts of the series were picked up into the nfsd, xfs,
  alsa and v4l2 trees. A final set of patches in linux-mm removes the
  now unused time_t/timeval/timespec types and helper functions after
  all five branches are merged for linux-5.6, ensuring that no new users
  get merged.

  As a result, linux-5.6, or my backport of the patches to 5.4 [1],
  should be the first release that can serve as a base for a 32-bit
  system designed to run beyond year 2038, with a few remaining caveats:

   - All user space must be compiled with a 64-bit time_t, which will be
     supported in the coming musl-1.2 and glibc-2.32 releases, along
     with installed kernel headers from linux-5.6 or higher.

   - Applications that use the system call interfaces directly need to
     be ported to use the time64 syscalls added in linux-5.1 in place of
     the existing system calls. This impacts most users of futex() and
     seccomp() as well as programming languages that have their own
     runtime environment not based on libc.

   - Applications that use a private copy of kernel uapi header files or
     their contents may need to update to the linux-5.6 version, in
     particular for sound/asound.h, xfs/xfs_fs.h, linux/input.h,
     linux/elfcore.h, linux/sockios.h, linux/timex.h and
     linux/can/bcm.h.

   - A few remaining interfaces cannot be changed to pass a 64-bit
     time_t in a compatible way, so they must be configured to use
     CLOCK_MONOTONIC times or (with a y2106 problem) unsigned 32-bit
     timestamps. Most importantly this impacts all users of 'struct
     input_event'.

   - All y2038 problems that are present on 64-bit machines also apply
     to 32-bit machines. In particular this affects file systems with
     on-disk timestamps using signed 32-bit seconds: ext4 with
     ext3-style small inodes, ext2, xfs (to be fixed soon) and ufs"

[1] https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/log/?h=y2038-endgame

* tag 'y2038-drivers-for-v5.6-signed' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground: (21 commits)
  Revert "drm/etnaviv: reject timeouts with tv_nsec >= NSEC_PER_SEC"
  y2038: sh: remove timeval/timespec usage from headers
  y2038: sparc: remove use of struct timex
  y2038: rename itimerval to __kernel_old_itimerval
  y2038: remove obsolete jiffies conversion functions
  nfs: fscache: use timespec64 in inode auxdata
  nfs: fix timstamp debug prints
  nfs: use time64_t internally
  sunrpc: convert to time64_t for expiry
  drm/etnaviv: avoid deprecated timespec
  drm/etnaviv: reject timeouts with tv_nsec >= NSEC_PER_SEC
  drm/msm: avoid using 'timespec'
  hfs/hfsplus: use 64-bit inode timestamps
  hostfs: pass 64-bit timestamps to/from user space
  packet: clarify timestamp overflow
  tsacct: add 64-bit btime field
  acct: stop using get_seconds()
  um: ubd: use 64-bit time_t where possible
  xtensa: ISS: avoid struct timeval
  dlm: use SO_SNDTIMEO_NEW instead of SO_SNDTIMEO_OLD
  ...
2020-01-29 14:55:47 -08:00
Linus Torvalds
e279160f49 The timekeeping and timers departement provides:
- Time namespace support:
 
     If a container migrates from one host to another then it expects that
     clocks based on MONOTONIC and BOOTTIME are not subject to
     disruption. Due to different boot time and non-suspended runtime these
     clocks can differ significantly on two hosts, in the worst case time
     goes backwards which is a violation of the POSIX requirements.
 
     The time namespace addresses this problem. It allows to set offsets for
     clock MONOTONIC and BOOTTIME once after creation and before tasks are
     associated with the namespace. These offsets are taken into account by
     timers and timekeeping including the VDSO.
 
     Offsets for wall clock based clocks (REALTIME/TAI) are not provided by
     this mechanism. While in theory possible, the overhead and code
     complexity would be immense and not justified by the esoteric potential
     use cases which were discussed at Plumbers '18.
 
     The overhead for tasks in the root namespace (host time offsets = 0) is
     in the noise and great effort was made to ensure that especially in the
     VDSO. If time namespace is disabled in the kernel configuration the
     code is compiled out.
 
     Kudos to Andrei Vagin and Dmitry Sofanov who implemented this feature
     and kept on for more than a year addressing review comments, finding
     better solutions. A pleasant experience.
 
   - Overhaul of the alarmtimer device dependency handling to ensure that
     the init/suspend/resume ordering is correct.
 
   - A new clocksource/event driver for Microchip PIT64
 
   - Suspend/resume support for the Hyper-V clocksource
 
   - The usual pile of fixes, updates and improvements mostly in the
     driver code.
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Merge tag 'timers-core-2020-01-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer updates from Thomas Gleixner:
 "The timekeeping and timers departement provides:

   - Time namespace support:

     If a container migrates from one host to another then it expects
     that clocks based on MONOTONIC and BOOTTIME are not subject to
     disruption. Due to different boot time and non-suspended runtime
     these clocks can differ significantly on two hosts, in the worst
     case time goes backwards which is a violation of the POSIX
     requirements.

     The time namespace addresses this problem. It allows to set offsets
     for clock MONOTONIC and BOOTTIME once after creation and before
     tasks are associated with the namespace. These offsets are taken
     into account by timers and timekeeping including the VDSO.

     Offsets for wall clock based clocks (REALTIME/TAI) are not provided
     by this mechanism. While in theory possible, the overhead and code
     complexity would be immense and not justified by the esoteric
     potential use cases which were discussed at Plumbers '18.

     The overhead for tasks in the root namespace (ie where host time
     offsets = 0) is in the noise and great effort was made to ensure
     that especially in the VDSO. If time namespace is disabled in the
     kernel configuration the code is compiled out.

     Kudos to Andrei Vagin and Dmitry Sofanov who implemented this
     feature and kept on for more than a year addressing review
     comments, finding better solutions. A pleasant experience.

   - Overhaul of the alarmtimer device dependency handling to ensure
     that the init/suspend/resume ordering is correct.

   - A new clocksource/event driver for Microchip PIT64

   - Suspend/resume support for the Hyper-V clocksource

   - The usual pile of fixes, updates and improvements mostly in the
     driver code"

* tag 'timers-core-2020-01-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (71 commits)
  alarmtimer: Make alarmtimer_get_rtcdev() a stub when CONFIG_RTC_CLASS=n
  alarmtimer: Use wakeup source from alarmtimer platform device
  alarmtimer: Make alarmtimer platform device child of RTC device
  alarmtimer: Update alarmtimer_get_rtcdev() docs to reflect reality
  hrtimer: Add missing sparse annotation for __run_timer()
  lib/vdso: Only read hrtimer_res when needed in __cvdso_clock_getres()
  MIPS: vdso: Define BUILD_VDSO32 when building a 32bit kernel
  clocksource/drivers/hyper-v: Set TSC clocksource as default w/ InvariantTSC
  clocksource/drivers/hyper-v: Untangle stimers and timesync from clocksources
  clocksource/drivers/timer-microchip-pit64b: Fix sparse warning
  clocksource/drivers/exynos_mct: Rename Exynos to lowercase
  clocksource/drivers/timer-ti-dm: Fix uninitialized pointer access
  clocksource/drivers/timer-ti-dm: Switch to platform_get_irq
  clocksource/drivers/timer-ti-dm: Convert to devm_platform_ioremap_resource
  clocksource/drivers/em_sti: Fix variable declaration in em_sti_probe
  clocksource/drivers/em_sti: Convert to devm_platform_ioremap_resource
  clocksource/drivers/bcm2835_timer: Fix memory leak of timer
  clocksource/drivers/cadence-ttc: Use ttc driver as platform driver
  clocksource/drivers/timer-microchip-pit64b: Add Microchip PIT64B support
  clocksource/drivers/hyper-v: Reserve PAGE_SIZE space for tsc page
  ...
2020-01-27 16:47:05 -08:00
Stephen Boyd
fd928f3e32 alarmtimer: Make alarmtimer_get_rtcdev() a stub when CONFIG_RTC_CLASS=n
The stubbed version of alarmtimer_get_rtcdev() is not exported.
so this won't work if this function is used in a module when
CONFIG_RTC_CLASS=n.

Move the stub function to the header file and make it inline so that
callers don't have to worry about linking against this symbol.

rtcdev isn't used outside of this ifdef so it's not required to be
redefined to NULL. Drop that while touching this area.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200124055849.154411-4-swboyd@chromium.org
2020-01-24 21:03:53 +01:00
Stephen Boyd
7c94caca87 alarmtimer: Use wakeup source from alarmtimer platform device
Use the wakeup source that can be associated with the 'alarmtimer'
platform device instead of registering another one by hand.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200124055849.154411-3-swboyd@chromium.org
2020-01-24 21:00:21 +01:00
Stephen Boyd
c79108bd19 alarmtimer: Make alarmtimer platform device child of RTC device
The alarmtimer_suspend() function will fail if an RTC device is on a bus
such as SPI or i2c and that RTC device registers and probes after
alarmtimer_init() registers and probes the 'alarmtimer' platform device.

This is because system wide suspend suspends devices in the reverse order
of their probe. When alarmtimer_suspend() attempts to program the RTC for a
wakeup it will try to program an RTC device on a bus that has already been
suspended.

Move the alarmtimer device registration to happen when the RTC which is
used for wakeup is registered. Register the 'alarmtimer' platform device as
a child of the RTC device too, so that it can be guaranteed that the RTC
device won't be suspended when alarmtimer_suspend() is called.

Reported-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200124055849.154411-2-swboyd@chromium.org
2020-01-24 21:00:20 +01:00
Stephen Boyd
6b088cefbe alarmtimer: Update alarmtimer_get_rtcdev() docs to reflect reality
This function doesn't do anything like this comment says when an RTC device
hasn't been chosen. It looks like we used to do something like that before
commit 8bc0dafb5c ("alarmtimers: Rework RTC device selection using class
interface") but that's long gone now. Remove this sentence to avoid
confusing the reader.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20200124055849.154411-5-swboyd@chromium.org
2020-01-24 21:00:20 +01:00