Commit graph

358 commits

Author SHA1 Message Date
Chun-Hung Tseng
24ba53017e rcu: Replace ________p1 and _________p1 with __UNIQUE_ID(rcu)
This commit replaces both ________p1 and _________p1 with __UNIQUE_ID(rcu),
and also adjusts the callers of the affected macros.

__UNIQUE_ID(rcu) will generate unique variable names during compilation,
which eliminates the need of ________p1 and _________p1 (both having 4
occurrences prior to the code change).  This also avoids the variable
name shadowing issue, or at least makes those wishing to cause shadowing
problems work much harder to do so.

The same idea is used for the min/max macros (commit 589a978 and commit
e9092d0).

Signed-off-by: Jim Huang <jserv@ccns.ncku.edu.tw>
Signed-off-by: Chun-Hung Tseng <henrybear327@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-11-30 17:25:20 -08:00
Waiman Long
925da92ba5 rcu: Avoid unneeded function call in rcu_read_unlock()
Since commit aa40c138cc ("rcu: Report QS for outermost PREEMPT=n
rcu_read_unlock() for strict GPs") the function rcu_read_unlock_strict()
is invoked by the inlined rcu_read_unlock() function.  However,
rcu_read_unlock_strict() is an empty function in production kernels,
which are built with CONFIG_RCU_STRICT_GRACE_PERIOD=n.

There is a mention of rcu_read_unlock_strict() in the BPF verifier,
but this is in a deny-list, meaning that BPF does not care whether
rcu_read_unlock_strict() is ever called.

This commit therefore provides a slight performance improvement
by hoisting the check of CONFIG_RCU_STRICT_GRACE_PERIOD from
rcu_read_unlock_strict() into rcu_read_unlock(), thus avoiding the
pointless call to an empty function.

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-09-16 10:24:05 -07:00
Paul E. McKenney
b770efc460 Merge branches 'doc.2021.07.20c', 'fixes.2021.08.06a', 'nocb.2021.07.20c', 'nolibc.2021.07.20c', 'tasks.2021.07.20c', 'torture.2021.07.27a' and 'torturescript.2021.07.27a' into HEAD
doc.2021.07.20c: Documentation updates.
fixes.2021.08.06a: Miscellaneous fixes.
nocb.2021.07.20c: Callback-offloading (NOCB CPU) updates.
nolibc.2021.07.20c: Tiny userspace library updates.
tasks.2021.07.20c: Tasks RCU updates.
torture.2021.07.27a: In-kernel torture-test updates.
torturescript.2021.07.27a: Torture-test scripting updates.
2021-08-10 11:00:53 -07:00
Paul E. McKenney
5fcb3a5f04 rcu: Mark accesses to ->rcu_read_lock_nesting
KCSAN flags accesses to ->rcu_read_lock_nesting as data races, but
in the past, the overhead of marked accesses was excessive.  However,
that was long ago, and much has changed since then, both in terms of
hardware and of compilers.  Here is data taken on an eight-core laptop
using Intel(R) Core(TM) i9-10885H CPU @ 2.40GHz with a kernel built
using gcc version 9.3.0, with all data in nanoseconds.

Unmarked accesses (status quo), measured by three refscale runs:

	Minimum reader duration:  3.286  2.851  3.395
	Median reader duration:   3.698  3.531  3.4695
	Maximum reader duration:  4.481  5.215  5.157

Marked accesses, also measured by three refscale runs:

	Minimum reader duration:  3.501  3.677  3.580
	Median reader duration:   4.053  3.723  3.895
	Maximum reader duration:  7.307  4.999  5.511

This focused microbenhmark shows only sub-nanosecond differences which
are unlikely to be visible at the system level.  This commit therefore
marks data-racing accesses to ->rcu_read_lock_nesting.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-08-06 13:41:48 -07:00
Zhouyi Zhou
fed31a4dd3 rcu: Fix macro name CONFIG_TASKS_RCU_TRACE
This commit fixes several typos where CONFIG_TASKS_RCU_TRACE should
instead be CONFIG_TASKS_TRACE_RCU.  Among other things, these typos
could cause CONFIG_TASKS_TRACE_RCU_READ_MB=y kernels to suffer from
memory-ordering bugs that could result in false-positive quiescent
states and too-short grace periods.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-07-20 13:43:44 -07:00
Paul E. McKenney
0223846010 rcu: Remove obsolete rcu_read_unlock() deadlock commentary
The deferred quiescent states resulting from the consolidation of RCU-bh
and RCU-sched into RCU means that rcu_read_unlock() will no longer attempt
to acquire scheduler locks if interrupts were disabled across that call
to rcu_read_unlock().  The cautions in the rcu_read_unlock() header
comment are therefore obsolete.  This commit therefore removes them.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-13 09:13:23 -07:00
Paul E. McKenney
1893afd634 rcu: Improve comments describing RCU read-side critical sections
There are a number of places that call out the fact that preempt-disable
regions of code now act as RCU read-side critical sections, where
preempt-disable regions of code include irq-disable regions of code,
bh-disable regions of code, hardirq handlers, and NMI handlers.  However,
someone relying solely on (for example) the call_rcu() header comment
might well have no idea that preempt-disable regions of code have RCU
semantics.

This commit therefore updates the header comments for
call_rcu(), synchronize_rcu(), rcu_dereference_bh_check(), and
rcu_dereference_sched_check() to call out these new(ish) forms of RCU
readers.

Reported-by: Michel Lespinasse <michel@lespinasse.org>
[ paulmck: Apply Matthew Wilcox and Michel Lespinasse feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-13 09:13:23 -07:00
Paul E. McKenney
76c8eaafe4 rcu: Create an unrcu_pointer() to remove __rcu from a pointer
The xchg() and cmpxchg() functions are sometimes used to carry out RCU
updates.  Unfortunately, this can result in sparse warnings for both
the old-value and new-value arguments, as well as for the return value.
The arguments can be dealt with using RCU_INITIALIZER():

	old_p = xchg(&p, RCU_INITIALIZER(new_p));

But a sparse warning still remains due to assigning the __rcu pointer
returned from xchg to the (most likely) non-__rcu pointer old_p.

This commit therefore provides an unrcu_pointer() macro that strips
the __rcu.  This macro can be used as follows:

	old_p = unrcu_pointer(xchg(&p, RCU_INITIALIZER(new_p)));

Reported-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-13 09:13:23 -07:00
Paul E. McKenney
3066820034 rcu: Reject RCU_LOCKDEP_WARN() false positives
If another lockdep report runs concurrently with an RCU lockdep report
from RCU_LOCKDEP_WARN(), the following sequence of events can occur:

1.	debug_lockdep_rcu_enabled() sees that lockdep is enabled
	when called from (say) synchronize_rcu().

2.	Lockdep is disabled by a concurrent lockdep report.

3.	debug_lockdep_rcu_enabled() evaluates its lockdep-expression
	argument, for example, lock_is_held(&rcu_bh_lock_map).

4.	Because lockdep is now disabled, lock_is_held() plays it safe and
	returns the constant 1.

5.	But in this case, the constant 1 is not safe, because invoking
	synchronize_rcu() under rcu_read_lock_bh() is disallowed.

6.	debug_lockdep_rcu_enabled() wrongly invokes lockdep_rcu_suspicious(),
	resulting in a false-positive splat.

This commit therefore changes RCU_LOCKDEP_WARN() to check
debug_lockdep_rcu_enabled() after checking the lockdep expression,
so that any "safe" returns from lock_is_held() are rejected by
debug_lockdep_rcu_enabled().  This requires memory ordering, which is
supplied by READ_ONCE(debug_locks).  The resulting volatile accesses
prevent the compiler from reordering and the fact that only one variable
is being accessed prevents the underlying hardware from reordering.
The combination works for IA64, which can reorder reads to the same
location, but this is defeated by the volatile accesses, which compile
to load instructions that provide ordering.

Reported-by: syzbot+dde0cc33951735441301@syzkaller.appspotmail.com
Reported-by: Matthew Wilcox <willy@infradead.org>
Reported-by: syzbot+88e4f02896967fe1ab0d@syzkaller.appspotmail.com
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-05-10 16:22:54 -07:00
Linus Torvalds
9a45da9270 RCU changes for this cycle were:
- Bitmap support for "N" as alias for last bit
  - kvfree_rcu updates
  - mm_dump_obj() updates.  (One of these is to mm, but was suggested by Andrew Morton.)
  - RCU callback offloading update
  - Polling RCU grace-period interfaces
  - Realtime-related RCU updates
  - Tasks-RCU updates
  - Torture-test updates
  - Torture-test scripting updates
  - Miscellaneous fixes
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'core-rcu-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull RCU updates from Ingo Molnar:

 - Support for "N" as alias for last bit in bitmap parsing library (eg
   using syntax like "nohz_full=2-N")

 - kvfree_rcu updates

 - mm_dump_obj() updates. (One of these is to mm, but was suggested by
   Andrew Morton.)

 - RCU callback offloading update

 - Polling RCU grace-period interfaces

 - Realtime-related RCU updates

 - Tasks-RCU updates

 - Torture-test updates

 - Torture-test scripting updates

 - Miscellaneous fixes

* tag 'core-rcu-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (77 commits)
  rcutorture: Test start_poll_synchronize_rcu() and poll_state_synchronize_rcu()
  rcu: Provide polling interfaces for Tiny RCU grace periods
  torture: Fix kvm.sh --datestamp regex check
  torture: Consolidate qemu-cmd duration editing into kvm-transform.sh
  torture: Print proper vmlinux path for kvm-again.sh runs
  torture: Make TORTURE_TRUST_MAKE available in kvm-again.sh environment
  torture: Make kvm-transform.sh update jitter commands
  torture: Add --duration argument to kvm-again.sh
  torture: Add kvm-again.sh to rerun a previous torture-test
  torture: Create a "batches" file for build reuse
  torture: De-capitalize TORTURE_SUITE
  torture: Make upper-case-only no-dot no-slash scenario names official
  torture: Rename SRCU-t and SRCU-u to avoid lowercase characters
  torture: Remove no-mpstat error message
  torture: Record kvm-test-1-run.sh and kvm-test-1-run-qemu.sh PIDs
  torture: Record jitter start/stop commands
  torture: Extract kvm-test-1-run-qemu.sh from kvm-test-1-run.sh
  torture: Record TORTURE_KCONFIG_GDB_ARG in qemu-cmd
  torture: Abstract jitter.sh start/stop into scripts
  rcu: Provide polling interfaces for Tree RCU grace periods
  ...
2021-04-28 12:00:13 -07:00
Thomas Gleixner
ba9e6cab49 rcu: Prevent false positive softirq warning on RT
Soft interrupt disabled sections can legitimately be preempted or schedule
out when blocking on a lock on RT enabled kernels so the RCU preempt check
warning has to be disabled for RT kernels.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210309085727.626304079@linutronix.de
2021-03-17 16:34:12 +01:00
Mauro Carvalho Chehab
e75956bd00 rcu: Fix kfree_rcu() docbook errors
After commit 5130b8fd06 ("rcu: Introduce kfree_rcu() single-argument macro"),
kernel-doc now emits two warnings:

	./include/linux/rcupdate.h:884: warning: Excess function parameter 'ptr' description in 'kfree_rcu'
	./include/linux/rcupdate.h:884: warning: Excess function parameter 'rhf' description in 'kfree_rcu'

This commit added some macro magic in order to call two different versions
of kfree_rcu(), the first having just one argument and the second having
two arguments.  That makes it difficult to document the kfree_rcu() arguments
in the docboook header.

In order to make clearer that this macro accepts optional arguments,
this commit uses macro concatenation so that this macro changes from:
	#define kfree_rcu kvfree_rcu

to:
	#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)

That not only helps kernel-doc understand the macro arguments, but also
provides a better C definition that makes clearer that the first argument
is mandatory and the second one is optional.

Fixes: 5130b8fd06 ("rcu: Introduce kfree_rcu() single-argument macro")
Tested-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-03-08 14:17:35 -08:00
Linus Torvalds
657bd90c93 Scheduler updates for v5.12:
[ NOTE: unfortunately this tree had to be freshly rebased today,
         it's a same-content tree of 82891be90f3c (-next published)
         merged with v5.11.
 
         The main reason for the rebase was an authorship misattribution
         problem with a new commit, which we noticed in the last minute,
         and which we didn't want to be merged upstream. The offending
         commit was deep in the tree, and dependent commits had to be
         rebased as well. ]
 
 - Core scheduler updates:
 
   - Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the
     preempt=none/voluntary/full boot options (default: full),
     to allow distros to build a PREEMPT kernel but fall back to
     close to PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling
     behavior via a boot time selection.
 
     There's also the /debug/sched_debug switch to do this runtime.
 
     This feature is implemented via runtime patching (a new variant of static calls).
 
     The scope of the runtime patching can be best reviewed by looking
     at the sched_dynamic_update() function in kernel/sched/core.c.
 
     ( Note that the dynamic none/voluntary mode isn't 100% identical,
       for example preempt-RCU is available in all cases, plus the
       preempt count is maintained in all models, which has runtime
       overhead even with the code patching. )
 
     The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast majority
     of distributions, are supposed to be unaffected.
 
   - Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that
     was found via rcutorture triggering a hang. The bug is that
     rcu_idle_enter() may wake up a NOCB kthread, but this happens after
     the last generic need_resched() check. Some cpuidle drivers fix it
     by chance but many others don't.
 
     In true 2020 fashion the original bug fix has grown into a 5-patch
     scheduler/RCU fix series plus another 16 RCU patches to address
     the underlying issue of missed preemption events. These are the
     initial fixes that should fix current incarnations of the bug.
 
   - Clean up rbtree usage in the scheduler, by providing & using the following
     consistent set of rbtree APIs:
 
      partial-order; less() based:
        - rb_add(): add a new entry to the rbtree
        - rb_add_cached(): like rb_add(), but for a rb_root_cached
 
      total-order; cmp() based:
        - rb_find(): find an entry in an rbtree
        - rb_find_add(): find an entry, and add if not found
 
        - rb_find_first(): find the first (leftmost) matching entry
        - rb_next_match(): continue from rb_find_first()
        - rb_for_each(): iterate a sub-tree using the previous two
 
   - Improve the SMP/NUMA load-balancer: scan for an idle sibling in a single pass.
     This is a 4-commit series where each commit improves one aspect of the idle
     sibling scan logic.
 
   - Improve the cpufreq cooling driver by getting the effective CPU utilization
     metrics from the scheduler
 
   - Improve the fair scheduler's active load-balancing logic by reducing the number
     of active LB attempts & lengthen the load-balancing interval. This improves
     stress-ng mmapfork performance.
 
   - Fix CFS's estimated utilization (util_est) calculation bug that can result in
     too high utilization values
 
 - Misc updates & fixes:
 
    - Fix the HRTICK reprogramming & optimization feature
    - Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code
    - Reduce dl_add_task_root_domain() overhead
    - Fix uprobes refcount bug
    - Process pending softirqs in flush_smp_call_function_from_idle()
    - Clean up task priority related defines, remove *USER_*PRIO and
      USER_PRIO()
    - Simplify the sched_init_numa() deduplication sort
    - Documentation updates
    - Fix EAS bug in update_misfit_status(), which degraded the quality
      of energy-balancing
    - Smaller cleanups
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Merge tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler updates from Ingo Molnar:
 "Core scheduler updates:

   - Add CONFIG_PREEMPT_DYNAMIC: this in its current form adds the
     preempt=none/voluntary/full boot options (default: full), to allow
     distros to build a PREEMPT kernel but fall back to close to
     PREEMPT_VOLUNTARY (or PREEMPT_NONE) runtime scheduling behavior via
     a boot time selection.

     There's also the /debug/sched_debug switch to do this runtime.

     This feature is implemented via runtime patching (a new variant of
     static calls).

     The scope of the runtime patching can be best reviewed by looking
     at the sched_dynamic_update() function in kernel/sched/core.c.

     ( Note that the dynamic none/voluntary mode isn't 100% identical,
       for example preempt-RCU is available in all cases, plus the
       preempt count is maintained in all models, which has runtime
       overhead even with the code patching. )

     The PREEMPT_VOLUNTARY/PREEMPT_NONE models, used by the vast
     majority of distributions, are supposed to be unaffected.

   - Fix ignored rescheduling after rcu_eqs_enter(). This is a bug that
     was found via rcutorture triggering a hang. The bug is that
     rcu_idle_enter() may wake up a NOCB kthread, but this happens after
     the last generic need_resched() check. Some cpuidle drivers fix it
     by chance but many others don't.

     In true 2020 fashion the original bug fix has grown into a 5-patch
     scheduler/RCU fix series plus another 16 RCU patches to address the
     underlying issue of missed preemption events. These are the initial
     fixes that should fix current incarnations of the bug.

   - Clean up rbtree usage in the scheduler, by providing & using the
     following consistent set of rbtree APIs:

       partial-order; less() based:
         - rb_add(): add a new entry to the rbtree
         - rb_add_cached(): like rb_add(), but for a rb_root_cached

       total-order; cmp() based:
         - rb_find(): find an entry in an rbtree
         - rb_find_add(): find an entry, and add if not found

         - rb_find_first(): find the first (leftmost) matching entry
         - rb_next_match(): continue from rb_find_first()
         - rb_for_each(): iterate a sub-tree using the previous two

   - Improve the SMP/NUMA load-balancer: scan for an idle sibling in a
     single pass. This is a 4-commit series where each commit improves
     one aspect of the idle sibling scan logic.

   - Improve the cpufreq cooling driver by getting the effective CPU
     utilization metrics from the scheduler

   - Improve the fair scheduler's active load-balancing logic by
     reducing the number of active LB attempts & lengthen the
     load-balancing interval. This improves stress-ng mmapfork
     performance.

   - Fix CFS's estimated utilization (util_est) calculation bug that can
     result in too high utilization values

  Misc updates & fixes:

   - Fix the HRTICK reprogramming & optimization feature

   - Fix SCHED_SOFTIRQ raising race & warning in the CPU offlining code

   - Reduce dl_add_task_root_domain() overhead

   - Fix uprobes refcount bug

   - Process pending softirqs in flush_smp_call_function_from_idle()

   - Clean up task priority related defines, remove *USER_*PRIO and
     USER_PRIO()

   - Simplify the sched_init_numa() deduplication sort

   - Documentation updates

   - Fix EAS bug in update_misfit_status(), which degraded the quality
     of energy-balancing

   - Smaller cleanups"

* tag 'sched-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits)
  sched,x86: Allow !PREEMPT_DYNAMIC
  entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point
  entry: Explicitly flush pending rcuog wakeup before last rescheduling point
  rcu/nocb: Trigger self-IPI on late deferred wake up before user resume
  rcu/nocb: Perform deferred wake up before last idle's need_resched() check
  rcu: Pull deferred rcuog wake up to rcu_eqs_enter() callers
  sched/features: Distinguish between NORMAL and DEADLINE hrtick
  sched/features: Fix hrtick reprogramming
  sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
  uprobes: (Re)add missing get_uprobe() in __find_uprobe()
  smp: Process pending softirqs in flush_smp_call_function_from_idle()
  sched: Harden PREEMPT_DYNAMIC
  static_call: Allow module use without exposing static_call_key
  sched: Add /debug/sched_preempt
  preempt/dynamic: Support dynamic preempt with preempt= boot option
  preempt/dynamic: Provide irqentry_exit_cond_resched() static call
  preempt/dynamic: Provide preempt_schedule[_notrace]() static calls
  preempt/dynamic: Provide cond_resched() and might_resched() static calls
  preempt: Introduce CONFIG_PREEMPT_DYNAMIC
  static_call: Provide DEFINE_STATIC_CALL_RET0()
  ...
2021-02-21 12:35:04 -08:00
Frederic Weisbecker
43789ef3f7 rcu/nocb: Perform deferred wake up before last idle's need_resched() check
Entering RCU idle mode may cause a deferred wake up of an RCU NOCB_GP
kthread (rcuog) to be serviced.

Usually a local wake up happening while running the idle task is handled
in one of the need_resched() checks carefully placed within the idle
loop that can break to the scheduler.

Unfortunately the call to rcu_idle_enter() is already beyond the last
generic need_resched() check and we may halt the CPU with a resched
request unhandled, leaving the task hanging.

Fix this with splitting the rcuog wakeup handling from rcu_idle_enter()
and place it before the last generic need_resched() check in the idle
loop. It is then assumed that no call to call_rcu() will be performed
after that in the idle loop until the CPU is put in low power mode.

Fixes: 96d3fd0d31 (rcu: Break call_rcu() deadlock involving scheduler and perf)
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210131230548.32970-3-frederic@kernel.org
2021-02-17 14:12:43 +01:00
Paul E. McKenney
0d2460ba61 Merge branches 'doc.2021.01.06a', 'fixes.2021.01.04b', 'kfree_rcu.2021.01.04a', 'mmdumpobj.2021.01.22a', 'nocb.2021.01.06a', 'rt.2021.01.04a', 'stall.2021.01.06a', 'torture.2021.01.12a' and 'tortureall.2021.01.06a' into HEAD
doc.2021.01.06a: Documentation updates.
fixes.2021.01.04b: Miscellaneous fixes.
kfree_rcu.2021.01.04a: kfree_rcu() updates.
mmdumpobj.2021.01.22a: Dump allocation point for memory blocks.
nocb.2021.01.06a: RCU callback offload updates and cblist segment lengths.
rt.2021.01.04a: Real-time updates.
stall.2021.01.06a: RCU CPU stall warning updates.
torture.2021.01.12a: Torture-test updates and polling SRCU grace-period API.
tortureall.2021.01.06a: Torture-test script updates.
2021-01-22 15:26:44 -08:00
Frederic Weisbecker
254e11efde rcu/nocb: Re-offload support
To re-offload the callback processing off of a CPU, it is necessary to
clear SEGCBLIST_SOFTIRQ_ONLY, set SEGCBLIST_OFFLOADED, and then notify
both the CB and GP kthreads so that they both set their own bit flag and
start processing the callbacks remotely.  The re-offloading worker is
then notified that it can stop the RCU_SOFTIRQ handler (or rcuc kthread,
as the case may be) from processing the callbacks locally.

Ordering must be carefully enforced so that the callbacks that used to be
processed locally without locking will have the same ordering properties
when they are invoked by the nocb CB and GP kthreads.

This commit makes this change.

Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
[ paulmck: Export rcu_nocb_cpu_offload(). ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-06 16:24:25 -08:00
Frederic Weisbecker
d97b078182 rcu/nocb: De-offloading CB kthread
To de-offload callback processing back onto a CPU, it is necessary to
clear SEGCBLIST_OFFLOAD and notify the nocb CB kthread, which will then
clear its own bit flag and go to sleep to stop handling callbacks.  This
commit makes that change.  It will also be necessary to notify the nocb
GP kthread in this same way, which is the subject of a follow-on commit.

Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
[ paulmck: Add export per kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-06 16:24:19 -08:00
Paul E. McKenney
8b5bd67cf6 srcu: Provide polling interfaces for Tiny SRCU grace periods
There is a need for a polling interface for SRCU grace
periods, so this commit supplies get_state_synchronize_srcu(),
start_poll_synchronize_srcu(), and poll_state_synchronize_srcu() for this
purpose.  The first can be used if future grace periods are inevitable
(perhaps due to a later call_srcu() invocation), the second if future
grace periods might not otherwise happen, and the third to check if a
grace period has elapsed since the corresponding call to either of the
first two.

As with get_state_synchronize_rcu() and cond_synchronize_rcu(),
the return value from either get_state_synchronize_srcu() or
start_poll_synchronize_srcu() must be passed in to a later call to
poll_state_synchronize_srcu().

Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
[ paulmck: Add EXPORT_SYMBOL_GPL() per kernel test robot feedback. ]
[ paulmck: Apply feedback from Neeraj Upadhyay. ]
Link: https://lore.kernel.org/lkml/20201117004017.GA7444@paulmck-ThinkPad-P72/
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04 13:53:38 -08:00
Uladzislau Rezki (Sony)
5ea5d1ed57 rcu: Eliminate the __kvfree_rcu() macro
This commit open-codes the __kvfree_rcu() macro, thus saving a
few lines of code and improving readability.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04 13:42:04 -08:00
Uladzislau Rezki (Sony)
5130b8fd06 rcu: Introduce kfree_rcu() single-argument macro
There is a kvfree_rcu() single argument macro that handles pointers
returned by kvmalloc(). Even though it also handles pointer returned by
kmalloc(), readability suffers.

This commit therefore updates the kfree_rcu() macro to explicitly pair
with kmalloc(), thus improving readability.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2021-01-04 13:42:04 -08:00
Linus Torvalds
36bbbd0e23 Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU fix from Paul McKenney:
 "This is a fix for a regression in the v5.10 merge window, but it was
  reported quite late in the v5.10 process, plus generating and testing
  the fix took some time.

  The regression is due to commit 36dadef23f ("kprobes: Init kprobes
  in early_initcall") which on powerpc can use RCU Tasks before
  initialization, resulting in boot failures.

  The fix is straightforward, simply moving initialization of RCU Tasks
  before the early_initcall()s. The fix has been exposed to -next and
  kbuild test robot testing, and has been tested by the PowerPC guys"

* 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  rcu-tasks: Move RCU-tasks initialization to before early_initcall()
2021-01-04 10:55:19 -08:00
Uladzislau Rezki (Sony)
1b04fa9900 rcu-tasks: Move RCU-tasks initialization to before early_initcall()
PowerPC testing encountered boot failures due to RCU Tasks not being
fully initialized until core_initcall() time.  This commit therefore
initializes RCU Tasks (along with Rude RCU and RCU Tasks Trace) just
before early_initcall() time, thus allowing waiting on RCU Tasks grace
periods from early_initcall() handlers.

Link: https://lore.kernel.org/rcu/87eekfh80a.fsf@dja-thinkpad.axtens.net/
Fixes: 36dadef23f ("kprobes: Init kprobes in early_initcall")
Tested-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-12-14 15:31:13 -08:00
Jakub Kicinski
65e9eb1ccf rcu: Prevent RCU_LOCKDEP_WARN() from swallowing the condition
We run into a unused variable warning in bridge code when variable is
only used inside the condition of rcu_dereference_protected().

 #define mlock_dereference(X, br) \
	rcu_dereference_protected(X, lockdep_is_held(&br->multicast_lock))

Since on builds with CONFIG_PROVE_RCU=n rcu_dereference_protected()
compiles to nothing the compiler doesn't see the variable use.

This commit therefore prevents this warning by adding the condition as
dead code.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
--
CC: paulmck@kernel.org
CC: josh@joshtriplett.org
CC: rostedt@goodmis.org
CC: mathieu.desnoyers@efficios.com
CC: joel@joelfernandes.org
CC: jiangshanlai@gmail.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-02 17:10:01 -08:00
Jakub Kicinski
891cd1f99d rcu: Un-hide lockdep maps for !LOCKDEP
Currently, variables used only within lockdep expressions are flagged as
unused, requiring that these variables' declarations be decorated with
either #ifdef or __maybe_unused.  This results in ugly code.  This commit
therefore causes the RCU lock maps to be visible even when lockdep is not
enabled, thus removing the need for these decorations.  This approach
further relies on dead-code elimination to remove any references to
functions or variables that are not available in non-lockdep kernels.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-11-02 17:09:59 -08:00
Joe Perches
33def8498f treewide: Convert macro and uses of __section(foo) to __section("foo")
Use a more generic form for __section that requires quotes to avoid
complications with clang and gcc differences.

Remove the quote operator # from compiler_attributes.h __section macro.

Convert all unquoted __section(foo) uses to quoted __section("foo").
Also convert __attribute__((section("foo"))) uses to __section("foo")
even if the __attribute__ has multiple list entry forms.

Conversion done using the script at:

    https://lore.kernel.org/lkml/75393e5ddc272dc7403de74d645e6c6e0f4e70eb.camel@perches.com/2-convert_section.pl

Signed-off-by: Joe Perches <joe@perches.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@gooogle.com>
Reviewed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-25 14:51:49 -07:00
Paul E. McKenney
7fbe67e46a Merge branch 'strictgp.2020.08.24a' into HEAD
strictgp.2020.08.24a: Strict grace periods for KASAN testing.
2020-09-03 09:47:42 -07:00
Paul E. McKenney
aa40c138cc rcu: Report QS for outermost PREEMPT=n rcu_read_unlock() for strict GPs
The CONFIG_PREEMPT=n instance of rcu_read_unlock is even more
aggressively than that of CONFIG_PREEMPT=y in deferring reporting
quiescent states to the RCU core.  This is just what is wanted in normal
use because it reduces overhead, but the resulting delay is not what
is wanted for kernels built with CONFIG_RCU_STRICT_GRACE_PERIOD=y.
This commit therefore adds an rcu_read_unlock_strict() function that
checks for exceptional conditions, and reports the newly started
quiescent state if it is safe to do so, also doing a spin-delay if
requested via rcutree.rcu_unlock_delay.  This commit also adds a call
to rcu_read_unlock_strict() from the CONFIG_PREEMPT=n instance of
__rcu_read_unlock().

[ paulmck: Fixed bug located by kernel test robot <lkp@intel.com> ]
Reported-by Jann Horn <jannh@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24 18:40:28 -07:00
Tobias Klauser
000601bb62 rcu: Fix kerneldoc comments in rcupdate.h
This commit fixes the kerneldoc comments for rcu_read_unlock_bh(),
rcu_read_unlock_sched() and rcu_head_after_call_rcu() so they e.g. get
properly linked in the API documentation. Also add parenthesis after
function names to match the notation used in other kerneldoc comments in
the same file.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24 18:36:08 -07:00
Uladzislau Rezki (Sony)
1835f475e3 rcu: Introduce single argument kvfree_rcu() interface
Make kvfree_rcu() capable of freeing objects that will not
embed an rcu_head within it. This saves storage overhead in
such objects. Reclaiming headless objects this way requires
only a single argument (pointer to the object).

After this patch, there are two ways to use kvfree_rcu():

a) kvfree_rcu(ptr, rhf);
    struct X {
        struct rcu_head rhf;
        unsigned char data[100];
    };

    void *ptr = kvmalloc(sizeof(struct X), GFP_KERNEL);
    if (ptr)
        kvfree_rcu(ptr, rhf);

b) kvfree_rcu(ptr);
    void *ptr = kvmalloc(some_bytes, GFP_KERNEL);
    if (ptr)
        kvfree_rcu(ptr);

Note that the headless usage (example b) can only be used in a code
that can sleep. This is enforced by the CONFIG_DEBUG_ATOMIC_SLEEP
option.

Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29 11:59:26 -07:00
Uladzislau Rezki (Sony)
ce4dce123f rcu: Introduce 2 arg kvfree_rcu() interface
kvmalloc() can allocate two types of objects: SLAB backed
and vmalloc backed. How it behaves depends on requested
object's size and memory pressure.

Add a kvfree_rcu() interface that can free memory allocated
via kvmalloc(). It is a simple alias to kfree_rcu() which
can now handle either type of object.

<snip>
    struct test_kvfree_rcu {
        struct rcu_head rcu;
        unsigned char array[100];
    };

    struct test_kvfree_rcu *p;

    p = kvmalloc(10 * PAGE_SIZE);
    if (p)
        kvfree_rcu(p, rcu);
<snip>

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29 11:59:25 -07:00
Uladzislau Rezki (Sony)
c408b215f5 rcu: Rename *_kfree_callback/*_kfree_rcu_offset/kfree_call_*
The following changes are introduced:

1. Rename rcu_invoke_kfree_callback() to rcu_invoke_kvfree_callback(),
as well as the associated trace events, so the rcu_kfree_callback(),
becomes rcu_kvfree_callback(). The reason is to be aligned with kvfree()
notation.

2. Rename __is_kfree_rcu_offset to __is_kvfree_rcu_offset. All RCU
paths use kvfree() now instead of kfree(), thus rename it.

3. Rename kfree_call_rcu() to the kvfree_call_rcu(). The reason is,
it is capable of freeing vmalloc() memory now. Do the same with
__kfree_rcu() macro, it becomes __kvfree_rcu(), the goal is the
same.

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-29 11:59:25 -07:00
Paul E. McKenney
43766c3ead rcu-tasks: Make RCU Tasks Trace make use of RCU scheduler hooks
This commit makes the calls to rcu_tasks_qs() detect and report
quiescent states for RCU tasks trace.  If the task is in a quiescent
state and if ->trc_reader_checked is not yet set, the task sets its own
->trc_reader_checked.  This will cause the grace-period kthread to
remove it from the holdout list if it still remains there.

[ paulmck: Fix conditional compilation per kbuild test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-27 11:03:52 -07:00
Paul E. McKenney
c84aad7654 rcu-tasks: Add an RCU-tasks rude variant
This commit adds a "rude" variant of RCU-tasks that has as quiescent
states schedule(), cond_resched_tasks_rcu_qs(), userspace execution,
and (in theory, anyway) cond_resched().  In other words, RCU-tasks rude
readers are regions of code with preemption disabled, but excluding code
early in the CPU-online sequence and late in the CPU-offline sequence.
Updates make use of IPIs and force an IPI and a context switch on each
online CPU.  This variant is useful in some situations in tracing.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
[ paulmck: Apply EXPORT_SYMBOL_GPL() feedback from Qiujun Huang. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Apply review feedback from Steve Rostedt. ]
2020-04-27 11:03:51 -07:00
Paul E. McKenney
5873b8a94e rcu-tasks: Refactor RCU-tasks to allow variants to be added
This commit splits out generic processing from RCU-tasks-specific
processing in order to allow additional flavors to be added.  It also
adds a def_bool TASKS_RCU_GENERIC to enable the common RCU-tasks
infrastructure code.

This is primarily, but not entirely, a code-movement commit.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-27 11:03:51 -07:00
Paul E. McKenney
0e247386d9 Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD
doc.2019.12.10a: Documentations updates
exp.2019.12.09a: Expedited grace-period updates
fixes.2020.01.24a: Miscellaneous fixes
kfree_rcu.2020.01.24a: Batch kfree_rcu() work
list.2020.01.10a: RCU-protected-list updates
preempt.2020.01.24a: Preemptible RCU updates
torture.2019.12.09a: Torture-test updates
2020-01-24 10:37:27 -08:00
Ben Dooks
e1350e8e0e rcu: Move rcu_{expedited,normal} definitions into rcupdate.h
This commit moves the rcu_{expedited,normal} definitions from
kernel/rcu/update.c to include/linux/rcupdate.h to make sure they are
in sync, and also to avoid the following warning from sparse:

kernel/ksysfs.c:150:5: warning: symbol 'rcu_expedited' was not declared. Should it be static?
kernel/ksysfs.c:167:5: warning: symbol 'rcu_normal' was not declared. Should it be static?

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-01-24 10:33:50 -08:00
Paul E. McKenney
4414abf891 rcu: Remove rcu_swap_protected()
Now that the calls to rcu_swap_protected() have been replaced by
rcu_replace_pointer(), this commit removes rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Shane M Seymour <shane.seymour@hpe.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
2019-12-12 10:24:52 -08:00
Sebastian Andrzej Siewior
90326f0521 rcu: Use CONFIG_PREEMPTION where appropriate
The config option `CONFIG_PREEMPT' is used for the preemption model
"Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled
when kernel preemption is enabled which is true for the preemption model
`CONFIG_PREEMPT' and `CONFIG_PREEMPT_RT'.

Use `CONFIG_PREEMPTION' if it applies to both preemption models and not
just to `CONFIG_PREEMPT'.

Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: rcu@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-09 12:37:51 -08:00
Lai Jiangshan
b3e627d3d5 rcu: Make PREEMPT_RCU be a modifier to TREE_RCU
Currently PREEMPT_RCU and TREE_RCU are mutually exclusive Kconfig
options.  But PREEMPT_RCU actually specifies a kind of TREE_RCU,
namely a preemptible TREE_RCU. This commit therefore makes PREEMPT_RCU
be a modifer to the TREE_RCU Kconfig option.  This has the benefit of
simplifying several of the #if expressions that formerly needed to
check both, but now need only check one or the other.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2019-12-09 12:37:51 -08:00
Linus Torvalds
168829ad09 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:

   - A comprehensive rewrite of the robust/PI futex code's exit handling
     to fix various exit races. (Thomas Gleixner et al)

   - Rework the generic REFCOUNT_FULL implementation using
     atomic_fetch_* operations so that the performance impact of the
     cmpxchg() loops is mitigated for common refcount operations.

     With these performance improvements the generic implementation of
     refcount_t should be good enough for everybody - and this got
     confirmed by performance testing, so remove ARCH_HAS_REFCOUNT and
     REFCOUNT_FULL entirely, leaving the generic implementation enabled
     unconditionally. (Will Deacon)

   - Other misc changes, fixes, cleanups"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
  lkdtm: Remove references to CONFIG_REFCOUNT_FULL
  locking/refcount: Remove unused 'refcount_error_report()' function
  locking/refcount: Consolidate implementations of refcount_t
  locking/refcount: Consolidate REFCOUNT_{MAX,SATURATED} definitions
  locking/refcount: Move saturation warnings out of line
  locking/refcount: Improve performance of generic REFCOUNT_FULL code
  locking/refcount: Move the bulk of the REFCOUNT_FULL implementation into the <linux/refcount.h> header
  locking/refcount: Remove unused refcount_*_checked() variants
  locking/refcount: Ensure integer operands are treated as signed
  locking/refcount: Define constants for saturation and max refcount values
  futex: Prevent exit livelock
  futex: Provide distinct return value when owner is exiting
  futex: Add mutex around futex exit
  futex: Provide state handling for exec() as well
  futex: Sanitize exit state handling
  futex: Mark the begin of futex exit explicitly
  futex: Set task::futex_state to DEAD right after handling futex exit
  futex: Split futex_mm_release() for exit/exec
  exit/exec: Seperate mm_release()
  futex: Replace PF_EXITPIDONE with a state
  ...
2019-11-26 16:02:40 -08:00
Paul E. McKenney
a63fc6b75c rcu: Upgrade rcu_swap_protected() to rcu_replace_pointer()
Although the rcu_swap_protected() macro follows the example of
swap(), the interactions with RCU make its update of its argument
somewhat counter-intuitive.  This commit therefore introduces
an rcu_replace_pointer() that returns the old value of the RCU
pointer instead of doing the argument update.  Once all the uses of
rcu_swap_protected() are updated to instead use rcu_replace_pointer(),
rcu_swap_protected() will be removed.

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
[ paulmck: From rcu_replace() to rcu_replace_pointer() per Ingo Molnar. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Shane M Seymour <shane.seymour@hpe.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
2019-10-30 08:43:08 -07:00
Qian Cai
5facae4f35 locking/lockdep: Remove unused @nested argument from lock_release()
Since the following commit:

  b4adfe8e05 ("locking/lockdep: Remove unused argument in __lock_release")

@nested is no longer used in lock_release(), so remove it from all
lock_release() calls and friends.

Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: airlied@linux.ie
Cc: akpm@linux-foundation.org
Cc: alexander.levin@microsoft.com
Cc: daniel@iogearbox.net
Cc: davem@davemloft.net
Cc: dri-devel@lists.freedesktop.org
Cc: duyuyang@gmail.com
Cc: gregkh@linuxfoundation.org
Cc: hannes@cmpxchg.org
Cc: intel-gfx@lists.freedesktop.org
Cc: jack@suse.com
Cc: jlbec@evilplan.or
Cc: joonas.lahtinen@linux.intel.com
Cc: joseph.qi@linux.alibaba.com
Cc: jslaby@suse.com
Cc: juri.lelli@redhat.com
Cc: maarten.lankhorst@linux.intel.com
Cc: mark@fasheh.com
Cc: mhocko@kernel.org
Cc: mripard@kernel.org
Cc: ocfs2-devel@oss.oracle.com
Cc: rodrigo.vivi@intel.com
Cc: sean@poorly.run
Cc: st@kernel.org
Cc: tj@kernel.org
Cc: tytso@mit.edu
Cc: vdavydov.dev@gmail.com
Cc: vincent.guittot@linaro.org
Cc: viro@zeniv.linux.org.uk
Link: https://lkml.kernel.org/r/1568909380-32199-1-git-send-email-cai@lca.pw
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-10-09 12:46:10 +02:00
Linus Torvalds
7e67a85999 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler updates from Ingo Molnar:

 - MAINTAINERS: Add Mark Rutland as perf submaintainer, Juri Lelli and
   Vincent Guittot as scheduler submaintainers. Add Dietmar Eggemann,
   Steven Rostedt, Ben Segall and Mel Gorman as scheduler reviewers.

   As perf and the scheduler is getting bigger and more complex,
   document the status quo of current responsibilities and interests,
   and spread the review pain^H^H^H^H fun via an increase in the Cc:
   linecount generated by scripts/get_maintainer.pl. :-)

 - Add another series of patches that brings the -rt (PREEMPT_RT) tree
   closer to mainline: split the monolithic CONFIG_PREEMPT dependencies
   into a new CONFIG_PREEMPTION category that will allow the eventual
   introduction of CONFIG_PREEMPT_RT. Still a few more hundred patches
   to go though.

 - Extend the CPU cgroup controller with uclamp.min and uclamp.max to
   allow the finer shaping of CPU bandwidth usage.

 - Micro-optimize energy-aware wake-ups from O(CPUS^2) to O(CPUS).

 - Improve the behavior of high CPU count, high thread count
   applications running under cpu.cfs_quota_us constraints.

 - Improve balancing with SCHED_IDLE (SCHED_BATCH) tasks present.

 - Improve CPU isolation housekeeping CPU allocation NUMA locality.

 - Fix deadline scheduler bandwidth calculations and logic when cpusets
   rebuilds the topology, or when it gets deadline-throttled while it's
   being offlined.

 - Convert the cpuset_mutex to percpu_rwsem, to allow it to be used from
   setscheduler() system calls without creating global serialization.
   Add new synchronization between cpuset topology-changing events and
   the deadline acceptance tests in setscheduler(), which were broken
   before.

 - Rework the active_mm state machine to be less confusing and more
   optimal.

 - Rework (simplify) the pick_next_task() slowpath.

 - Improve load-balancing on AMD EPYC systems.

 - ... and misc cleanups, smaller fixes and improvements - please see
   the Git log for more details.

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits)
  sched/psi: Correct overly pessimistic size calculation
  sched/fair: Speed-up energy-aware wake-ups
  sched/uclamp: Always use 'enum uclamp_id' for clamp_id values
  sched/uclamp: Update CPU's refcount on TG's clamp changes
  sched/uclamp: Use TG's clamps to restrict TASK's clamps
  sched/uclamp: Propagate system defaults to the root group
  sched/uclamp: Propagate parent clamps
  sched/uclamp: Extend CPU's cgroup controller
  sched/topology: Improve load balancing on AMD EPYC systems
  arch, ia64: Make NUMA select SMP
  sched, perf: MAINTAINERS update, add submaintainers and reviewers
  sched/fair: Use rq_lock/unlock in online_fair_sched_group
  cpufreq: schedutil: fix equation in comment
  sched: Rework pick_next_task() slow-path
  sched: Allow put_prev_task() to drop rq->lock
  sched/fair: Expose newidle_balance()
  sched: Add task_struct pointer to sched_class::set_curr_task
  sched: Rework CPU hotplug task selection
  sched/{rt,deadline}: Fix set_next_task vs pick_next_task
  sched: Fix kerneldoc comment for ia64_set_curr_task
  ...
2019-09-16 17:25:49 -07:00
Joel Fernandes (Google)
28875945ba rcu: Add support for consolidated-RCU reader checking
This commit adds RCU-reader checks to list_for_each_entry_rcu() and
hlist_for_each_entry_rcu().  These checks are optional, and are indicated
by a lockdep expression passed to a new optional argument to these two
macros.  If this optional lockdep expression is omitted, these two macros
act as before, checking for an RCU read-side critical section.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Update to eliminate return within macro and update comment. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-09 11:00:35 -07:00
Joel Fernandes (Google)
0a5b99f578 treewide: Rename rcu_dereference_raw_notrace() to _check()
The rcu_dereference_raw_notrace() API name is confusing.  It is equivalent
to rcu_dereference_raw() except that it also does sparse pointer checking.

There are only a few users of rcu_dereference_raw_notrace(). This patches
renames all of them to be rcu_dereference_raw_check() with the "_check()"
indicating sparse checking.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Fix checkpatch warnings about parentheses. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-08-01 14:16:21 -07:00
Thomas Gleixner
01b1d88b09 rcu: Use CONFIG_PREEMPTION
CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by
CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same
functionality which today depends on CONFIG_PREEMPT.

Switch the conditionals in RCU to use CONFIG_PREEMPTION.

That's the first step towards RCU on RT. The further tweaks are work in
progress. This neither touches the selftest bits which need a closer look
by Paul.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20190726212124.210156346@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-07-31 19:03:35 +02:00
Ingo Molnar
83086d654d Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu
Pull rcu/next + tools/memory-model changes from Paul E. McKenney:

 - RCU flavor consolidation cleanups and optmizations
 - Documentation updates
 - Miscellaneous fixes
 - SRCU updates
 - RCU-sync flavor consolidation
 - Torture-test updates
 - Linux-kernel memory-consistency-model updates, most notably the addition of plain C-language accesses

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-06-28 19:46:47 +02:00
Andrea Parri
9129b017b5 rcu: Don't return a value from rcu_assign_pointer()
Quoting Paul [1]:

  "Given that a quick (and perhaps error-prone) search of the uses
   of rcu_assign_pointer() in v5.1 didn't find a single use of the
   return value, let's please instead change the documentation and
   implementation to eliminate the return value."

[1] https://lkml.kernel.org/r/20190523135013.GL28207@linux.ibm.com

Signed-off-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: "Paul E. McKenney" <paulmck@linux.ibm.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: rcu@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-06-13 15:38:34 -07:00
Waiman Long
6da9f77517 rcu: Force inlining of rcu_read_lock()
When debugging options are turned on, the rcu_read_lock() function
might not be inlined. This results in lockdep's print_lock() function
printing "rcu_read_lock+0x0/0x70" instead of rcu_read_lock()'s caller.
For example:

[   10.579995] =============================
[   10.584033] WARNING: suspicious RCU usage
[   10.588074] 4.18.0.memcg_v2+ #1 Not tainted
[   10.593162] -----------------------------
[   10.597203] include/linux/rcupdate.h:281 Illegal context switch in
RCU read-side critical section!
[   10.606220]
[   10.606220] other info that might help us debug this:
[   10.606220]
[   10.614280]
[   10.614280] rcu_scheduler_active = 2, debug_locks = 1
[   10.620853] 3 locks held by systemd/1:
[   10.624632]  #0: (____ptrval____) (&type->i_mutex_dir_key#5){.+.+}, at: lookup_slow+0x42/0x70
[   10.633232]  #1: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70
[   10.640954]  #2: (____ptrval____) (rcu_read_lock){....}, at: rcu_read_lock+0x0/0x70

These "rcu_read_lock+0x0/0x70" strings are not providing any useful
information.  This commit therefore forces inlining of the rcu_read_lock()
function so that rcu_read_lock()'s caller is instead shown.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-06-13 15:38:33 -07:00
Paul E. McKenney
b3119cde1d rcu: Fix irritating whitespace error in rcu_assign_pointer()
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
2019-06-13 15:38:33 -07:00