The expedited kthread worker performing the per node initialization is
going to be split into per node kthreads. As such, the future per node
kthread creation will need to be called from CPU hotplug callbacks
instead of an initcall, right beside the per node boost kthread
creation.
To prepare for that, move the kthread worker creation above
rcutree_prepare_cpu() as a first step to make the review smoother for
the upcoming modifications.
No intended functional change.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
This mutex is currently protecting per node boost kthreads creation and
affinity setting across CPU hotplug operations.
Since the expedited kworkers will soon be split per node as well, they
will be subject to the same concurrency constraints against hotplug.
Therefore their creation and affinity tuning operations will be grouped
with those of boost kthreads and then rely on the same mutex.
To prepare for that, generalize its name.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Just like is done for the kworker performing nodes initialization,
gracefully handle the possible allocation failure of the RCU expedited
grace period main kworker.
While at it perform a rename of the related checking functions to better
reflect the expedited specifics.
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Fixes: 9621fbee44 ("rcu: Move expedited grace period (GP) work to RT kthread_worker")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Under CONFIG_RCU_EXP_KTHREAD=y, the nodes initialization for expedited
grace periods is queued to a kworker. However if the allocation of that
kworker failed, the nodes initialization is performed synchronously by
the caller instead.
Now the check for kworker initialization failure relies on the kworker
pointer to be NULL while its value might actually encapsulate an
allocation failure error.
Make sure to handle this case.
Reviewed-by: Kalesh Singh <kaleshsingh@google.com>
Fixes: 9621fbee44 ("rcu: Move expedited grace period (GP) work to RT kthread_worker")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
When an expedited grace period is ending, care must be taken so that all
the quiescent states propagated up to the root are correctly ordered
against the wake up of the main expedited grace period workqueue.
This ordering is already carried through the root rnp locking augmented
by an smp_mb__after_unlock_lock() barrier.
Therefore the explicit smp_mb() placed before the wake up is not needed
and can be removed.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Currently, only rdp_gp->nocb_timer is used, for nocb_timer of
no-rdp_gp structure, the timer_pending() is always return false,
this commit therefore need to check rdp_gp->nocb_timer in
__call_rcu_nocb_wake().
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and
CONFIG_RCU_LAZY=y, the following scenarios will trigger WARN_ON_ONCE()
in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended() functions:
CPU2 CPU11
kthread
rcu_nocb_cb_kthread ksys_write
rcu_do_batch vfs_write
rcu_torture_timer_cb proc_sys_write
__kmem_cache_free proc_sys_call_handler
kmemleak_free drop_caches_sysctl_handler
delete_object_full drop_slab
__delete_object shrink_slab
put_object lazy_rcu_shrink_scan
call_rcu rcu_nocb_flush_bypass
__call_rcu_commn rcu_nocb_bypass_lock
raw_spin_trylock(&rdp->nocb_bypass_lock) fail
atomic_inc(&rdp->nocb_lock_contended);
rcu_nocb_wait_contended WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) |
|_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ _ _ _ _ _ _ _ _ __|
Reproduce this bug with "echo 3 > /proc/sys/vm/drop_caches".
This commit therefore uses rcu_nocb_try_flush_bypass() instead of
rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(). If the nocb_bypass
queue is being flushed, then rcu_nocb_try_flush_bypass will return
directly.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Currently the call_rcu() function interleaves NOCB and !NOCB enqueue
code in a complicated way such that:
* The bypass enqueue code may or may not have enqueued and may or may
not have locked the ->nocb_lock. Everything that follows is in a
Schrödinger locking state for the unwary reviewer's eyes.
* The was_alldone is always set but only used in NOCB related code.
* The NOCB wake up is distantly related to the locking hopefully
performed by the bypass enqueue code that did not enqueue on the
bypass list.
Unconfuse the whole and gather NOCB and !NOCB specific enqueue code to
their own functions.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Currently IRQs are disabled on call_rcu() and then depending on the
context:
* If the CPU is in nocb mode:
- If the callback is enqueued in the bypass list, IRQs are re-enabled
implictly by rcu_nocb_try_bypass()
- If the callback is enqueued in the normal list, IRQs are re-enabled
implicitly by __call_rcu_nocb_wake()
* If the CPU is NOT in nocb mode, IRQs are reenabled explicitly from call_rcu()
This makes the code a bit hard to follow, especially as it interleaves
with nocb locking.
To make the IRQ flags coverage clearer and also in order to prepare for
moving all the nocb enqueue code to its own function, always re-enable
the IRQ flags explicitly from call_rcu().
Reviewed-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
A full barrier is issued from nocb_gp_wait() upon callbacks advancing
to order grace period completion with callbacks execution.
However these two events are already ordered by the
smp_mb__after_unlock_lock() barrier within the call to
raw_spin_lock_rcu_node() that is necessary for callbacks advancing to
happen.
The following litmus test shows the kind of guarantee that this barrier
provides:
C smp_mb__after_unlock_lock
{}
// rcu_gp_cleanup()
P0(spinlock_t *rnp_lock, int *gpnum)
{
// Grace period cleanup increase gp sequence number
spin_lock(rnp_lock);
WRITE_ONCE(*gpnum, 1);
spin_unlock(rnp_lock);
}
// nocb_gp_wait()
P1(spinlock_t *rnp_lock, spinlock_t *nocb_lock, int *gpnum, int *cb_ready)
{
int r1;
// Call rcu_advance_cbs() from nocb_gp_wait()
spin_lock(nocb_lock);
spin_lock(rnp_lock);
smp_mb__after_unlock_lock();
r1 = READ_ONCE(*gpnum);
WRITE_ONCE(*cb_ready, 1);
spin_unlock(rnp_lock);
spin_unlock(nocb_lock);
}
// nocb_cb_wait()
P2(spinlock_t *nocb_lock, int *cb_ready, int *cb_executed)
{
int r2;
// rcu_do_batch() -> rcu_segcblist_extract_done_cbs()
spin_lock(nocb_lock);
r2 = READ_ONCE(*cb_ready);
spin_unlock(nocb_lock);
// Actual callback execution
WRITE_ONCE(*cb_executed, 1);
}
P3(int *cb_executed, int *gpnum)
{
int r3;
WRITE_ONCE(*cb_executed, 2);
smp_mb();
r3 = READ_ONCE(*gpnum);
}
exists (1:r1=1 /\ 2:r2=1 /\ cb_executed=2 /\ 3:r3=0) (* Bad outcome. *)
Here the bad outcome only occurs if the smp_mb__after_unlock_lock() is
removed. This barrier orders the grace period completion against
callbacks advancing and even later callbacks invocation, thanks to the
opportunistic propagation via the ->nocb_lock to nocb_cb_wait().
Therefore the smp_mb() placed after callbacks advancing can be safely
removed.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
The LOAD-ACQUIRE access performed on rdp->nocb_cb_sleep advertizes
ordering callback execution against grace period completion. However
this is contradicted by the following:
* This LOAD-ACQUIRE doesn't pair with anything. The only counterpart
barrier that can be found is the smp_mb() placed after callbacks
advancing in nocb_gp_wait(). However the barrier is placed _after_
->nocb_cb_sleep write.
* Callbacks can be concurrently advanced between the LOAD-ACQUIRE on
->nocb_cb_sleep and the call to rcu_segcblist_extract_done_cbs() in
rcu_do_batch(), making any ordering based on ->nocb_cb_sleep broken.
* Both rcu_segcblist_extract_done_cbs() and rcu_advance_cbs() are called
under the nocb_lock, the latter hereby providing already the desired
ACQUIRE semantics.
Therefore it is safe to access ->nocb_cb_sleep with a simple compiler
barrier.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
When the CPU goes idle for the last time during the CPU down hotplug
process, RCU reports a final quiescent state for the current CPU. If
this quiescent state propagates up to the top, some tasks may then be
woken up to complete the grace period: the main grace period kthread
and/or the expedited main workqueue (or kworker).
If those kthreads have a SCHED_FIFO policy, the wake up can indirectly
arm the RT bandwith timer to the local offline CPU. Since this happens
after hrtimers have been migrated at CPUHP_AP_HRTIMERS_DYING stage, the
timer gets ignored. Therefore if the RCU kthreads are waiting for RT
bandwidth to be available, they may never be actually scheduled.
This triggers TREE03 rcutorture hangs:
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 4-...!: (1 GPs behind) idle=9874/1/0x4000000000000000 softirq=0/0 fqs=20 rcuc=21071 jiffies(starved)
rcu: (t=21035 jiffies g=938281 q=40787 ncpus=6)
rcu: rcu_preempt kthread starved for 20964 jiffies! g938281 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt state:R running task stack:14896 pid:14 tgid:14 ppid:2 flags:0x00004000
Call Trace:
<TASK>
__schedule+0x2eb/0xa80
schedule+0x1f/0x90
schedule_timeout+0x163/0x270
? __pfx_process_timeout+0x10/0x10
rcu_gp_fqs_loop+0x37c/0x5b0
? __pfx_rcu_gp_kthread+0x10/0x10
rcu_gp_kthread+0x17c/0x200
kthread+0xde/0x110
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2b/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1b/0x30
</TASK>
The situation can't be solved with just unpinning the timer. The hrtimer
infrastructure and the nohz heuristics involved in finding the best
remote target for an unpinned timer would then also need to handle
enqueues from an offline CPU in the most horrendous way.
So fix this on the RCU side instead and defer the wake up to an online
CPU if it's too late for the local one.
Reported-by: Paul E. McKenney <paulmck@kernel.org>
Fixes: 5c0930ccaa ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
If an rcutorture test scenario creates an fqs_task kthread, it will
periodically invoke rcu_force_quiescent_state() in order to start
force-quiescent-state (FQS) operations. However, an FQS operation
will be started even if there is no RCU grace period in progress.
Although testing FQS operations startup when there is no grace period in
progress is necessary, it need not happen all that often. This commit
therefore causes rcu_force_quiescent_state() to take an early exit
if there is no grace period in progress.
Note that there will still be attempts to start an FQS scan in the
absence of a grace period because the grace period might end right
after the rcu_force_quiescent_state() function's check. In actual
testing, this happens about once every ten minutes, which should
provide adequate testing.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
If an SRCU barrier is queued while callbacks are running and a new
callbacks invocator for the same sdp were to run concurrently, the
RCU barrier might execute too early. As this requirement is non-obvious,
make sure to keep a record.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
While in grace period start, there is nothing to accelerate and
therefore no need to advance the callbacks either if no callback is
to be enqueued.
Spare these needless operations in this case.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Callbacks advancing on SRCU must be performed on two specific places:
1) On enqueue time in order to make room for the acceleration of the
new callback.
2) On invocation time in order to move the callbacks ready to invoke.
Any other callback advancing callsite is needless. Remove the remaining
one in srcu_gp_start().
Co-developed-by: Yong He <zhuangel570@gmail.com>
Signed-off-by: Yong He <zhuangel570@gmail.com>
Co-developed-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Co-developed-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Although the RCU CPU stall notifiers can be useful for dumping state when
tracking down delicate forward-progress bugs where NUMA effects cause
cache lines to be delivered to a given CPU regularly, but always in a
state that prevents that CPU from making forward progress. These bugs can
be detected by the RCU CPU stall-warning mechanism, but in some cases,
the stall-warnings printk()s disrupt the forward-progress bug before
any useful state can be obtained.
Unfortunately, the notifier mechanism added by commit 5b404fdaba ("rcu:
Add RCU CPU stall notifier") can make matters worse if used at all
carelessly. For example, if the stall warning was caused by a lock not
being released, then any attempt to acquire that lock in the notifier
will hang. This will prevent not only the notifier from producing any
useful output, but it will also prevent the stall-warning message from
ever appearing.
This commit therefore hides this new RCU CPU stall notifier
mechanism under a new RCU_CPU_STALL_NOTIFIER Kconfig option that
depends on both DEBUG_KERNEL and RCU_EXPERT. In addition, the
rcupdate.rcu_cpu_stall_notifiers=1 kernel boot parameter must also
be specified. The RCU_CPU_STALL_NOTIFIER Kconfig option's help text
contains a warning and explains the dangers of careless use, recommending
lockless notifier code. In addition, a WARN() is triggered each time
that an attempt is made to register a stall-warning notifier in kernels
built with CONFIG_RCU_CPU_STALL_NOTIFIER=y.
This combination of measures will keep use of this mechanism confined to
debug kernels and away from routine deployments.
[ paulmck: Apply Dan Carpenter feedback. ]
Fixes: 5b404fdaba ("rcu: Add RCU CPU stall notifier")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
The task_struct structure's ->rcu_tasks_idle_cpu can be concurrently
read and written from the RCU Tasks grace-period kthread and from the
CPU on which the task_struct structure's task is running. This commit
therefore marks the accesses appropriately.
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
For rcutorture tests on RCU implementations that support
force-quiescent-state operations and that set the fqs_duration module
parameter greater than zero, the fqs_task kthread will be created.
However, if the fqs_holdoff module parameter is not set, then its default
value of zero will cause fqs_task enter a long-term busy loop until
stopped by kthread_stop(). This commit therefore adds a fqs_holdoff
check before the fqs_task is created, making sure that whenever the
fqs_task is created, the fqs_holdoff will be greater than zero.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
* Fix a lock inversion between scheduler and RCU introduced
in v6.2-rc4. The scenario could trigger on any user of RCU_NOCB
(mostly Android and also nohz_full).
* Fix PF_IDLE semantic changes introduced in v6.6-rc3 breaking some
RCU-Tasks and RCU-Tasks-Trace expectations as to what exactly is
an idle task. This resulted in potential spurious stalls and
warnings.
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Merge tag 'rcu-fixes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks
Pull RCU fixes from Frederic Weisbecker:
- Fix a lock inversion between scheduler and RCU introduced in
v6.2-rc4. The scenario could trigger on any user of RCU_NOCB
(mostly Android but also nohz_full)
- Fix PF_IDLE semantic changes introduced in v6.6-rc3 breaking
some RCU-Tasks and RCU-Tasks-Trace expectations as to what
exactly is an idle task. This resulted in potential spurious
stalls and warnings.
* tag 'rcu-fixes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks:
rcu/tasks-trace: Handle new PF_IDLE semantics
rcu/tasks: Handle new PF_IDLE semantics
rcu: Introduce rcu_cpu_online()
rcu: Break rcu_node_0 --> &rq->__lock order
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series "Fixes and cleanups to compaction".
- Joel Fernandes has a patchset ("Optimize mremap during mutual
alignment within PMD") which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested.
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i the
following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series "Do not try to access unaccepted memory" Adrian Hunter
provides some fixups for the recently-added "unaccepted memory' feature.
To increase the feature's checking coverage. "Plug a few gaps where
RAM is exposed without checking if it is unaccepted memory".
- In the series "cleanups for lockless slab shrink" Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code.
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series "use refcount+RCU method to implement
lockless slab shrink".
- David Hildenbrand contributes some maintenance work for the rmap code
in the series "Anon rmap cleanups".
- Kefeng Wang does more folio conversions and some maintenance work in
the migration code. Series "mm: migrate: more folio conversion and
unification".
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series "Add and use bdev_getblk()".
- In the series "Use nth_page() in place of direct struct page
manipulation" Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames.
- In the series "mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO" has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of gigantic
pages are in use.
- Matthew Wilcox has sent the series "Small hugetlb cleanups" - code
rationalization and folio conversions in the hugetlb code.
- Yin Fengwei has improved mlock()'s handling of large folios in the
series "support large folio for mlock"
- In the series "Expose swapcache stat for memcg v1" Liu Shixin has
added statistics for memcg v1 users which are available (and useful)
under memcg v2.
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named "MDWE
without inheritance".
- Kefeng Wang has provided the series "mm: convert numa balancing
functions to use a folio" which does what it says.
- In the series "mm/ksm: add fork-exec support for prctl" Stefan Roesch
makes is possible for a process to propagate KSM treatment across
exec().
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use "high
bandwidth memory" in addition to Optane Data Center Persistent Memory
Modules (DCPMM). The series is named "memory tiering: calculate
abstract distance based on ACPI HMAT"
- In the series "Smart scanning mode for KSM" Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans.
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in the
series "mm: memcg: fix tracking of pending stats updates values".
- In the series "Implement IOCTL to get and optionally clear info about
PTEs" Peter Xu has added an ioctl to /proc/<pid>/pagemap which permits
us to atomically read-then-clear page softdirty state. This is mainly
used by CRIU.
- Hugh Dickins contributed the series "shmem,tmpfs: general maintenance"
- a bunch of relatively minor maintenance tweaks to this code.
- Matthew Wilcox has increased the use of the VMA lock over file-backed
page faults in the series "Handle more faults under the VMA lock". Some
rationalizations of the fault path became possible as a result.
- In the series "mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()" David Hildenbrand has implemented some cleanups
and folio conversions.
- In the series "various improvements to the GUP interface" Lorenzo
Stoakes has simplified and improved the GUP interface with an eye to
providing groundwork for future improvements.
- Andrey Konovalov has sent along the series "kasan: assorted fixes and
improvements" which does those things.
- Some page allocator maintenance work from Kemeng Shi in the series
"Two minor cleanups to break_down_buddy_pages".
- In thes series "New selftest for mm" Breno Leitao has developed
another MM self test which tickles a race we had between madvise() and
page faults.
- In the series "Add folio_end_read" Matthew Wilcox provides cleanups
and an optimization to the core pagecache code.
- Nhat Pham has added memcg accounting for hugetlb memory in the series
"hugetlb memcg accounting".
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series "Abstract vma_merge() and split_vma()".
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series "Fix page_owner's use of free timestamps".
- Lorenzo Stoakes has fixed the handling of new mappings of sealed files
in the series "permit write-sealed memfd read-only shared mappings".
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series "Batch hugetlb vmemmap modification operations".
- Some buffer_head folio conversions and cleanups from Matthew Wilcox in
the series "Finish the create_empty_buffers() transition".
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the series
"mm: PCP high auto-tuning".
- Roman Gushchin has contributed the patchset "mm: improve performance
of accounted kernel memory allocations" which improves their performance
by ~30% as measured by a micro-benchmark.
- folio conversions from Kefeng Wang in the series "mm: convert page
cpupid functions to folios".
- Some kmemleak fixups in Liu Shixin's series "Some bugfix about
kmemleak".
- Qi Zheng has improved our handling of memoryless nodes by keeping them
off the allocation fallback list. This is done in the series "handle
memoryless nodes more appropriately".
- khugepaged conversions from Vishal Moola in the series "Some
khugepaged folio conversions".
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Merge tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
"Many singleton patches against the MM code. The patch series which are
included in this merge do the following:
- Kemeng Shi has contributed some compation maintenance work in the
series 'Fixes and cleanups to compaction'
- Joel Fernandes has a patchset ('Optimize mremap during mutual
alignment within PMD') which fixes an obscure issue with mremap()'s
pagetable handling during a subsequent exec(), based upon an
implementation which Linus suggested
- More DAMON/DAMOS maintenance and feature work from SeongJae Park i
the following patch series:
mm/damon: misc fixups for documents, comments and its tracepoint
mm/damon: add a tracepoint for damos apply target regions
mm/damon: provide pseudo-moving sum based access rate
mm/damon: implement DAMOS apply intervals
mm/damon/core-test: Fix memory leaks in core-test
mm/damon/sysfs-schemes: Do DAMOS tried regions update for only one apply interval
- In the series 'Do not try to access unaccepted memory' Adrian
Hunter provides some fixups for the recently-added 'unaccepted
memory' feature. To increase the feature's checking coverage. 'Plug
a few gaps where RAM is exposed without checking if it is
unaccepted memory'
- In the series 'cleanups for lockless slab shrink' Qi Zheng has done
some maintenance work which is preparation for the lockless slab
shrinking code
- Qi Zheng has redone the earlier (and reverted) attempt to make slab
shrinking lockless in the series 'use refcount+RCU method to
implement lockless slab shrink'
- David Hildenbrand contributes some maintenance work for the rmap
code in the series 'Anon rmap cleanups'
- Kefeng Wang does more folio conversions and some maintenance work
in the migration code. Series 'mm: migrate: more folio conversion
and unification'
- Matthew Wilcox has fixed an issue in the buffer_head code which was
causing long stalls under some heavy memory/IO loads. Some cleanups
were added on the way. Series 'Add and use bdev_getblk()'
- In the series 'Use nth_page() in place of direct struct page
manipulation' Zi Yan has fixed a potential issue with the direct
manipulation of hugetlb page frames
- In the series 'mm: hugetlb: Skip initialization of gigantic tail
struct pages if freed by HVO' has improved our handling of gigantic
pages in the hugetlb vmmemmep optimizaton code. This provides
significant boot time improvements when significant amounts of
gigantic pages are in use
- Matthew Wilcox has sent the series 'Small hugetlb cleanups' - code
rationalization and folio conversions in the hugetlb code
- Yin Fengwei has improved mlock()'s handling of large folios in the
series 'support large folio for mlock'
- In the series 'Expose swapcache stat for memcg v1' Liu Shixin has
added statistics for memcg v1 users which are available (and
useful) under memcg v2
- Florent Revest has enhanced the MDWE (Memory-Deny-Write-Executable)
prctl so that userspace may direct the kernel to not automatically
propagate the denial to child processes. The series is named 'MDWE
without inheritance'
- Kefeng Wang has provided the series 'mm: convert numa balancing
functions to use a folio' which does what it says
- In the series 'mm/ksm: add fork-exec support for prctl' Stefan
Roesch makes is possible for a process to propagate KSM treatment
across exec()
- Huang Ying has enhanced memory tiering's calculation of memory
distances. This is used to permit the dax/kmem driver to use 'high
bandwidth memory' in addition to Optane Data Center Persistent
Memory Modules (DCPMM). The series is named 'memory tiering:
calculate abstract distance based on ACPI HMAT'
- In the series 'Smart scanning mode for KSM' Stefan Roesch has
optimized KSM by teaching it to retain and use some historical
information from previous scans
- Yosry Ahmed has fixed some inconsistencies in memcg statistics in
the series 'mm: memcg: fix tracking of pending stats updates
values'
- In the series 'Implement IOCTL to get and optionally clear info
about PTEs' Peter Xu has added an ioctl to /proc/<pid>/pagemap
which permits us to atomically read-then-clear page softdirty
state. This is mainly used by CRIU
- Hugh Dickins contributed the series 'shmem,tmpfs: general
maintenance', a bunch of relatively minor maintenance tweaks to
this code
- Matthew Wilcox has increased the use of the VMA lock over
file-backed page faults in the series 'Handle more faults under the
VMA lock'. Some rationalizations of the fault path became possible
as a result
- In the series 'mm/rmap: convert page_move_anon_rmap() to
folio_move_anon_rmap()' David Hildenbrand has implemented some
cleanups and folio conversions
- In the series 'various improvements to the GUP interface' Lorenzo
Stoakes has simplified and improved the GUP interface with an eye
to providing groundwork for future improvements
- Andrey Konovalov has sent along the series 'kasan: assorted fixes
and improvements' which does those things
- Some page allocator maintenance work from Kemeng Shi in the series
'Two minor cleanups to break_down_buddy_pages'
- In thes series 'New selftest for mm' Breno Leitao has developed
another MM self test which tickles a race we had between madvise()
and page faults
- In the series 'Add folio_end_read' Matthew Wilcox provides cleanups
and an optimization to the core pagecache code
- Nhat Pham has added memcg accounting for hugetlb memory in the
series 'hugetlb memcg accounting'
- Cleanups and rationalizations to the pagemap code from Lorenzo
Stoakes, in the series 'Abstract vma_merge() and split_vma()'
- Audra Mitchell has fixed issues in the procfs page_owner code's new
timestamping feature which was causing some misbehaviours. In the
series 'Fix page_owner's use of free timestamps'
- Lorenzo Stoakes has fixed the handling of new mappings of sealed
files in the series 'permit write-sealed memfd read-only shared
mappings'
- Mike Kravetz has optimized the hugetlb vmemmap optimization in the
series 'Batch hugetlb vmemmap modification operations'
- Some buffer_head folio conversions and cleanups from Matthew Wilcox
in the series 'Finish the create_empty_buffers() transition'
- As a page allocator performance optimization Huang Ying has added
automatic tuning to the allocator's per-cpu-pages feature, in the
series 'mm: PCP high auto-tuning'
- Roman Gushchin has contributed the patchset 'mm: improve
performance of accounted kernel memory allocations' which improves
their performance by ~30% as measured by a micro-benchmark
- folio conversions from Kefeng Wang in the series 'mm: convert page
cpupid functions to folios'
- Some kmemleak fixups in Liu Shixin's series 'Some bugfix about
kmemleak'
- Qi Zheng has improved our handling of memoryless nodes by keeping
them off the allocation fallback list. This is done in the series
'handle memoryless nodes more appropriately'
- khugepaged conversions from Vishal Moola in the series 'Some
khugepaged folio conversions'"
[ bcachefs conflicts with the dynamically allocated shrinkers have been
resolved as per Stephen Rothwell in
https://lore.kernel.org/all/20230913093553.4290421e@canb.auug.org.au/
with help from Qi Zheng.
The clone3 test filtering conflict was half-arsed by yours truly ]
* tag 'mm-stable-2023-11-01-14-33' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (406 commits)
mm/damon/sysfs: update monitoring target regions for online input commit
mm/damon/sysfs: remove requested targets when online-commit inputs
selftests: add a sanity check for zswap
Documentation: maple_tree: fix word spelling error
mm/vmalloc: fix the unchecked dereference warning in vread_iter()
zswap: export compression failure stats
Documentation: ubsan: drop "the" from article title
mempolicy: migration attempt to match interleave nodes
mempolicy: mmap_lock is not needed while migrating folios
mempolicy: alloc_pages_mpol() for NUMA policy without vma
mm: add page_rmappable_folio() wrapper
mempolicy: remove confusing MPOL_MF_LAZY dead code
mempolicy: mpol_shared_policy_init() without pseudo-vma
mempolicy trivia: use pgoff_t in shared mempolicy tree
mempolicy trivia: slightly more consistent naming
mempolicy trivia: delete those ancient pr_debug()s
mempolicy: fix migrate_pages(2) syscall return nr_failed
kernfs: drop shared NUMA mempolicy hooks
hugetlbfs: drop shared NUMA mempolicy pretence
mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()
...
The commit:
cff9b2332a ("kernel/sched: Modify initial boot task idle setup")
has changed the semantics of what is to be considered an idle task in
such a way that the idle task of an offline CPU may not carry the
PF_IDLE flag anymore.
However RCU-tasks-trace tests the opposite assertion, still assuming
that idle tasks carry the PF_IDLE flag during their whole lifecycle.
Remove this assumption to avoid spurious warnings but keep the initial
test verifying that the idle task is the current task on any offline
CPU.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: cff9b2332a ("kernel/sched: Modify initial boot task idle setup")
Suggested-by: Joel Fernandes <joel@joelfernandes.org>
Suggested-by: Paul E . McKenney" <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The commit:
cff9b2332a ("kernel/sched: Modify initial boot task idle setup")
has changed the semantics of what is to be considered an idle task in
such a way that CPU boot code preceding the actual idle loop is excluded
from it.
This has however introduced new potential RCU-tasks stalls when either:
1) Grace period is started before init/0 had a chance to set PF_IDLE,
keeping it stuck in the holdout list until idle ever schedules.
2) Grace period is started when some possible CPUs have never been
online, keeping their idle tasks stuck in the holdout list until the
CPU ever boots up.
3) Similar to 1) but with secondary CPUs: Grace period is started
concurrently with secondary CPU booting, putting its idle task in
the holdout list because PF_IDLE isn't yet observed on it. It stays
then stuck in the holdout list until that CPU ever schedules. The
effect is mitigated here by the hotplug AP thread that must run to
bring the CPU up.
Fix this with handling the new semantics of PF_IDLE, keeping in mind
that it may or may not be set on an idle task. Take advantage of that to
strengthen the coverage of an RCU-tasks quiescent state within an idle
task, excluding the CPU boot code from it. Only the code running within
the idle loop is now a quiescent state, along with offline CPUs.
Fixes: cff9b2332a ("kernel/sched: Modify initial boot task idle setup")
Suggested-by: Joel Fernandes <joel@joelfernandes.org>
Suggested-by: Paul E . McKenney" <paulmck@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Export the RCU point of view as to when a CPU is considered offline
(ie: when does RCU consider that a CPU is sufficiently down in the
hotplug process to not feature any possible read side).
This will be used by RCU-tasks whose vision of an offline CPU should
reasonably match the one of RCU core.
Fixes: cff9b2332a ("kernel/sched: Modify initial boot task idle setup")
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Commit 851a723e45 ("sched: Always clear user_cpus_ptr in
do_set_cpus_allowed()") added a kfree() call to free any user
provided affinity mask, if present. It was changed later to use
kfree_rcu() in commit 9a5418bc48 ("sched/core: Use kfree_rcu()
in do_set_cpus_allowed()") to avoid a circular locking dependency
problem.
It turns out that even kfree_rcu() isn't safe for avoiding
circular locking problem. As reported by kernel test robot,
the following circular locking dependency now exists:
&rdp->nocb_lock --> rcu_node_0 --> &rq->__lock
Solve this by breaking the rcu_node_0 --> &rq->__lock chain by moving
the resched_cpu() out from under rcu_node lock.
[peterz: heavily borrowed from Waiman's Changelog]
[paulmck: applied Z qiang feedback]
Fixes: 851a723e45 ("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()")
Reported-by: kernel test robot <oliver.sang@intel.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/oe-lkp/202310302207.a25f1a30-oliver.sang@intel.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Acceleration in SRCU happens on enqueue time for each new callback. This
operation is expected not to fail and therefore any similar attempt
from other places shouldn't find any remaining callbacks to accelerate.
Moreover accelerations performed beyond enqueue time are error prone
because rcu_seq_snap() then may return the snapshot for a new grace
period that is not going to be started.
Remove these dangerous and needless accelerations and introduce instead
assertions reporting leaking unaccelerated callbacks beyond enqueue
time.
Co-developed-by: Yong He <alexyonghe@tencent.com>
Signed-off-by: Yong He <alexyonghe@tencent.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Neeraj upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Neeraj upadhyay <Neeraj.Upadhyay@amd.com>
Reviewed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
SRCU callbacks acceleration might fail if the preceding callbacks
advance also fails. This can happen when the following steps are met:
1) The RCU_WAIT_TAIL segment has callbacks (say for gp_num 8) and the
RCU_NEXT_READY_TAIL also has callbacks (say for gp_num 12).
2) The grace period for RCU_WAIT_TAIL is observed as started but not yet
completed so rcu_seq_current() returns 4 + SRCU_STATE_SCAN1 = 5.
3) This value is passed to rcu_segcblist_advance() which can't move
any segment forward and fails.
4) srcu_gp_start_if_needed() still proceeds with callback acceleration.
But then the call to rcu_seq_snap() observes the grace period for the
RCU_WAIT_TAIL segment (gp_num 8) as completed and the subsequent one
for the RCU_NEXT_READY_TAIL segment as started
(ie: 8 + SRCU_STATE_SCAN1 = 9) so it returns a snapshot of the
next grace period, which is 16.
5) The value of 16 is passed to rcu_segcblist_accelerate() but the
freshly enqueued callback in RCU_NEXT_TAIL can't move to
RCU_NEXT_READY_TAIL which already has callbacks for a previous grace
period (gp_num = 12). So acceleration fails.
6) Note in all these steps, srcu_invoke_callbacks() hadn't had a chance
to run srcu_invoke_callbacks().
Then some very bad outcome may happen if the following happens:
7) Some other CPU races and starts the grace period number 16 before the
CPU handling previous steps had a chance. Therefore srcu_gp_start()
isn't called on the latter sdp to fix the acceleration leak from
previous steps with a new pair of call to advance/accelerate.
8) The grace period 16 completes and srcu_invoke_callbacks() is finally
called. All the callbacks from previous grace periods (8 and 12) are
correctly advanced and executed but callbacks in RCU_NEXT_READY_TAIL
still remain. Then rcu_segcblist_accelerate() is called with a
snaphot of 20.
9) Since nothing started the grace period number 20, callbacks stay
unhandled.
This has been reported in real load:
[3144162.608392] INFO: task kworker/136:12:252684 blocked for more
than 122 seconds.
[3144162.615986] Tainted: G O K 5.4.203-1-tlinux4-0011.1 #1
[3144162.623053] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs"
disables this message.
[3144162.631162] kworker/136:12 D 0 252684 2 0x90004000
[3144162.631189] Workqueue: kvm-irqfd-cleanup irqfd_shutdown [kvm]
[3144162.631192] Call Trace:
[3144162.631202] __schedule+0x2ee/0x660
[3144162.631206] schedule+0x33/0xa0
[3144162.631209] schedule_timeout+0x1c4/0x340
[3144162.631214] ? update_load_avg+0x82/0x660
[3144162.631217] ? raw_spin_rq_lock_nested+0x1f/0x30
[3144162.631218] wait_for_completion+0x119/0x180
[3144162.631220] ? wake_up_q+0x80/0x80
[3144162.631224] __synchronize_srcu.part.19+0x81/0xb0
[3144162.631226] ? __bpf_trace_rcu_utilization+0x10/0x10
[3144162.631227] synchronize_srcu+0x5f/0xc0
[3144162.631236] irqfd_shutdown+0x3c/0xb0 [kvm]
[3144162.631239] ? __schedule+0x2f6/0x660
[3144162.631243] process_one_work+0x19a/0x3a0
[3144162.631244] worker_thread+0x37/0x3a0
[3144162.631247] kthread+0x117/0x140
[3144162.631247] ? process_one_work+0x3a0/0x3a0
[3144162.631248] ? __kthread_cancel_work+0x40/0x40
[3144162.631250] ret_from_fork+0x1f/0x30
Fix this with taking the snapshot for acceleration _before_ the read
of the current grace period number.
The only side effect of this solution is that callbacks advancing happen
then _after_ the full barrier in rcu_seq_snap(). This is not a problem
because that barrier only cares about:
1) Ordering accesses of the update side before call_srcu() so they don't
bleed.
2) See all the accesses prior to the grace period of the current gp_num
The only things callbacks advancing need to be ordered against are
carried by snp locking.
Reported-by: Yong He <alexyonghe@tencent.com>
Co-developed-by:: Yong He <alexyonghe@tencent.com>
Signed-off-by: Yong He <alexyonghe@tencent.com>
Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Co-developed-by: Neeraj upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Neeraj upadhyay <Neeraj.Upadhyay@amd.com>
Link: http://lore.kernel.org/CANZk6aR+CqZaqmMWrC2eRRPY12qAZnDZLwLnHZbNi=xXMB401g@mail.gmail.com
Fixes: da915ad5cf ("srcu: Parallelize callback handling")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
rcu_report_dead() and rcutree_migrate_callbacks() have their headers in
rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug
functions.
Also rcu_cpu_starting() and rcu_report_dead() have different naming
conventions while they mirror each other's effects.
Fix the headers and propose a naming that relates both functions and
aligns with the prefix of other rcutree CPU-hotplug functions.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Among the three CPU-hotplug teardown RCU callbacks, two of them early
exit if CONFIG_HOTPLUG_CPU=n, and one is left unchanged. In any case
all of them have an implementation when CONFIG_HOTPLUG_CPU=n.
Align instead with the common way to deal with CPU-hotplug teardown
callbacks and provide a proper stub when they are not supported.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
rcu_report_dead() has to be called locally by the CPU that is going to
exit the RCU state machine. Passing a cpu argument here is error-prone
and leaves the possibility for a racy remote call.
Use local access instead.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
rcu_report_dead() is the last RCU word from the CPU down through the
hotplug path. It is called in the idle loop right before the CPU shuts
down for good. Because it removes the CPU from the grace period state
machine and reports an ultimate quiescent state if necessary, no further
use of RCU is allowed. Therefore it is expected that IRQs are disabled
upon calling this function and are not to be re-enabled again until the
CPU shuts down.
Remove the IRQs disablement from that function and verify instead that
it is actually called with IRQs disabled as it is expected at that
special point in the idle path.
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This makes the code more readable.
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Since the actual slab freeing is deferred when calling kvfree_rcu(), so
is the kmemleak_free() callback informing kmemleak of the object
deletion. From the perspective of the kvfree_rcu() caller, the object is
freed and it may remove any references to it. Since kmemleak does not
scan RCU internal data storing the pointer, it will report such objects
as leaks during the grace period.
Tell kmemleak to ignore such objects on the kvfree_call_rcu() path. Note
that the tiny RCU implementation does not have such issue since the
objects can be tracked from the rcu_ctrlblk structure.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Christoph Paasch <cpaasch@apple.com>
Closes: https://lore.kernel.org/all/F903A825-F05F-4B77-A2B5-7356282FBA2C@apple.com/
Cc: <stable@vger.kernel.org>
Tested-by: Christoph Paasch <cpaasch@apple.com>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The value of a bitwise expression 1 << (cpu - sdp->mynode->grplo)
is subject to overflow due to a failure to cast operands to a larger
data type before performing the bitwise operation.
The maximum result of this subtraction is defined by the RCU_FANOUT_LEAF
Kconfig option, which on 64-bit systems defaults to 16 (resulting in a
maximum shift of 15), but which can be set up as high as 64 (resulting
in a maximum shift of 63). A value of 31 can result in sign extension,
resulting in 0xffffffff80000000 instead of the desired 0x80000000.
A value of 32 or greater triggers undefined behavior per the C standard.
This bug has not been known to cause issues because almost all kernels
take the default CONFIG_RCU_FANOUT_LEAF=16. Furthermore, as long as a
given compiler gives a deterministic non-zero result for 1<<N for N>=32,
the code correctly invokes all SRCU callbacks, albeit wasting CPU time
along the way.
This commit therefore substitutes the correct 1UL for the buggy 1.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Signed-off-by: Denis Arefev <arefev@swemel.ru>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: David Laight <David.Laight@aculab.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Currently, the maxcpu is set by traversing online CPUs, however, if the
rcutorture.onoff_holdoff is set zero and onoff_interval is set non-zero,
and the some CPUs with larger cpuid has been offline before setting
maxcpu, for these CPUs, even if they are online again, also cannot
be offload or deoffload. This can result in rcutorture attempting to
(de-)offload CPUs that have never been online, but the (de-)offload code
handles this.
This commit therefore use for_each_possible_cpu() instead of
for_each_online_cpu() in rcu_nocb_toggle().
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
In the past, spinning on schedule_timeout* with a wait of 1 jiffy has
hung the kernel. See for example d52d3a2bf4 ("torture: Fix hang during
kthread shutdown phase").
This issue recently recurred in torture's stutter code. The result is
that the function instantly returns and never goes to sleep, preempting
whatever might otherwise make useful forward progress.
To prevent future issues, apply the commit-d52d3a2bf408 fix throughout
rcutorture, moving from a 1-jiffy wait to a 50-millisecond wait.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The rcutorture_sched_setaffinity() function is needed by locktorture,
so move its declaration from rcu.h to torture.h and rename it to the
more generic torture_sched_setaffinity() name.
Please note that use of this function is still restricted to torture
tests, and of those, currently only rcutorture and locktorture.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The prototype for torture_sched_setaffinity() will be moved to a
different header, which will need to be included from update.c to avoid
this W=1 warning:
kernel/rcu/update.c:529:6: error: no previous prototype for 'torture_sched_setaffinity' [-Werror=missing-prototypes]
529 | long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
When using rcutorture as a module, there are a number of conditions that
can abort the modprobe operation, for example, when attempting to run
both RCU CPU stall warning tests and forward-progress tests. This can
cause rcu_torture_cleanup() to be invoked on the unwind path out of
rcu_rcu_torture_init(), which will mean that rcu_gp_slow_unregister()
is invoked without a matching rcu_gp_slow_register(). This will cause
a splat because rcu_gp_slow_unregister() is passed rcu_fwd_cb_nodelay,
which does not match a NULL pointer.
This commit therefore forgives a mismatch involving a NULL pointer, thus
avoiding this false-positive splat.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
When a structure containing an RCU callback rhp is (incorrectly) freed
and reallocated after rhp is passed to call_rcu(), it is not unusual for
rhp->func to be set to NULL. This defeats the debugging prints used by
__call_rcu_common() in kernels built with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y,
which expect to identify the offending code using the identity of this
function.
And in kernels build without CONFIG_DEBUG_OBJECTS_RCU_HEAD=y, things
are even worse, as can be seen from this splat:
Unable to handle kernel NULL pointer dereference at virtual address 0
... ...
PC is at 0x0
LR is at rcu_do_batch+0x1c0/0x3b8
... ...
(rcu_do_batch) from (rcu_core+0x1d4/0x284)
(rcu_core) from (__do_softirq+0x24c/0x344)
(__do_softirq) from (__irq_exit_rcu+0x64/0x108)
(__irq_exit_rcu) from (irq_exit+0x8/0x10)
(irq_exit) from (__handle_domain_irq+0x74/0x9c)
(__handle_domain_irq) from (gic_handle_irq+0x8c/0x98)
(gic_handle_irq) from (__irq_svc+0x5c/0x94)
(__irq_svc) from (arch_cpu_idle+0x20/0x3c)
(arch_cpu_idle) from (default_idle_call+0x4c/0x78)
(default_idle_call) from (do_idle+0xf8/0x150)
(do_idle) from (cpu_startup_entry+0x18/0x20)
(cpu_startup_entry) from (0xc01530)
This commit therefore adds calls to mem_dump_obj(rhp) to output some
information, for example:
slab kmalloc-256 start ffff410c45019900 pointer offset 0 size 256
This provides the rough size of the memory block and the offset of the
rcu_head structure, which as least provides at least a few clues to help
locate the problem. If the problem is reproducible, additional slab
debugging can be enabled, for example, CONFIG_DEBUG_SLAB=y, which can
provide significantly more information.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
When running a series of stress tests all making heavy use of RCU,
it is all too possible to OOM the system when the prior test's RCU
callbacks don't get invoked until after the subsequent test starts.
One way of handling this is just a timed wait, but this fails when a
given CPU has so many callbacks queued that they take longer to invoke
than allowed for by that timed wait.
This commit therefore adds an rcutree.do_rcu_barrier module parameter that
is accessible from sysfs. Writing one of the many synonyms for boolean
"true" will cause an rcu_barrier() to be invoked, but will guarantee that
no more than one rcu_barrier() will be invoked per sixteenth of a second
via this mechanism. The flip side is that a given request might wait a
second or three longer than absolutely necessary, but only when there are
multiple uses of rcutree.do_rcu_barrier within a one-second time interval.
This commit unnecessarily serializes the rcu_barrier() machinery, given
that serialization is already provided by procfs. This has the advantage
of allowing throttled rcu_barrier() from other sources within the kernel.
Reported-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The return keyword is not needed here.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The current error handling in init_srcu_struct_fields() is a bit
inconsistent. If init_srcu_struct_nodes() fails, the function either
returns -ENOMEM or 0 depending on whether ssp->sda_is_static is true or
false. This can make init_srcu_struct_fields() return 0 even if memory
allocation failed!
Simplify the error handling by always returning -ENOMEM if either
init_srcu_struct_nodes() or the per-CPU allocation fails. This makes the
control flow easier to follow and avoids the inconsistent return values.
Add goto labels to avoid duplicating the error cleanup code.
Link: https://lore.kernel.org/r/20230404003508.GA254019@google.com
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The refscale.verbose_batched and refscale.lookup_instances module
parameters are omitted from the ref_scale_print_module_parms()
beginning-of-test output. This commit therefore adds them.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This commit fixes a misplaced data re-read in the typesafe code.
The reason that this was not noticed is that this is a performance test
with no writers, so a mismatch could not occur.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The rcu_tasks_lazy_ms variable is not used outside the file tasks.h,
so this commit marks it static.
kernel/rcu/tasks.h:1085:5: warning: symbol 'rcu_tasks_lazy_ms' was not declared. Should it be static?
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=6086
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The rcu_tasks_need_gpcb() samples ->percpu_dequeue_lim as part of the
condition clause of a "for" loop, which is a bit confusing. This commit
therefore hoists this sampling out of the loop, using the result loaded
in the condition clause.
So why does this work in the face of a concurrent switch from single-CPU
queueing to per-CPU queueing?
o The call_rcu_tasks_generic() that makes the change has already
enqueued its callback, which means that all of the other CPU's
callback queues are empty.
o For the call_rcu_tasks_generic() that first notices
the switch to per-CPU queues, the smp_store_release()
used to update ->percpu_enqueue_lim pairs with the
raw_spin_trylock_rcu_node()'s full barrier that is
between the READ_ONCE(rtp->percpu_enqueue_shift) and the
rcu_segcblist_enqueue() that enqueues the callback.
o Because this CPU's queue is empty (unless it happens to
be the original single queue, in which case there is no
need for synchronization), this call_rcu_tasks_generic()
will do an irq_work_queue() to schedule a handler for the
needed rcuwait_wake_up() call. This call will be ordered
after the first call_rcu_tasks_generic() function's change to
->percpu_dequeue_lim.
o This rcuwait_wake_up() will either happen before or after the
set_current_state() in rcuwait_wait_event(). If it happens
before, the "condition" argument's call to rcu_tasks_need_gpcb()
will be ordered after the original change, and all callbacks on
all CPUs will be visible. Otherwise, if it happens after, then
the grace-period kthread's state will be set back to running,
which will result in a later call to rcuwait_wait_event() and
thus to rcu_tasks_need_gpcb(), which will again see the change.
So it all works out.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Currently, rcu_tasks_initiate_self_tests() prints a message and then
initiates self tests on up to three different RCU Tasks flavors. If one
of the flavors has a grace-period hang, it is not easy to work out which
of the three hung. This commit therefore prints a message prior to each
individual test.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
There are instances where rcu_cpu_stall_reset() is called when jiffies
did not get a chance to update for a long time. Before jiffies is
updated, the CPU stall detector can go off triggering false-positives
where a just-started grace period appears to be ages old. In the past,
we disabled stall detection in rcu_cpu_stall_reset() however this got
changed [1]. This is resulting in false-positives in KGDB usecase [2].
Fix this by deferring the update of jiffies to the third run of the FQS
loop. This is more robust, as, even if rcu_cpu_stall_reset() is called
just before jiffies is read, we would end up pushing out the jiffies
read by 3 more FQS loops. Meanwhile the CPU stall detection will be
delayed and we will not get any false positives.
[1] https://lore.kernel.org/all/20210521155624.174524-2-senozhatsky@chromium.org/
[2] https://lore.kernel.org/all/20230814020045.51950-2-chenhuacai@loongson.cn/
Tested with rcutorture.cpu_stall option as well to verify stall behavior
with/without patch.
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Reported-by: Binbin Zhou <zhoubinbin@loongson.cn>
Closes: https://lore.kernel.org/all/20230814020045.51950-2-chenhuacai@loongson.cn/
Suggested-by: Paul McKenney <paulmck@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: a80be428fb ("rcu: Do not disable GP stall detection in rcu_cpu_stall_reset()")
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This commit registers an RCU CPU stall notifier when testing RCU CPU
stalls. The notifier logs a message similar to the following:
rcu_torture_stall_nf: v=1, duration=21001.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
It is sometimes helpful to have a way for the subsystem causing
the stall to dump its state when an RCU CPU stall occurs. This
commit therefore bases rcu_stall_chain_notifier_register() and
rcu_stall_chain_notifier_unregister() on atomic notifiers in order to
provide this functionality.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The code and comments of self-detected and other-detected RCU CPU stall
warnings are identical except the output function. This commit therefore
refactors so as to consolidate the duplicate code.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The stacks of all stalled CPUs will be dumped in rcu_dump_cpu_stacks().
If the CPU on where RCU GP kthread last ran is stalled, its stack does
not need to be dumped again. We can search the corresponding backtrace
based on the printed CPU ID.
For example:
[ 87.328275] rcu: rcu_sched kthread starved for ... ->cpu=3 <--------|
... ... |
[ 89.385007] NMI backtrace for cpu 3 <--------|
[ 89.385179] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 5.10.0+ #22 <--|
[ 89.385188] Hardware name: linux,dummy-virt (DT)
[ 89.385196] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
[ 89.385204] pc : arch_cpu_idle+0x40/0xc0
[ 89.385211] lr : arch_cpu_idle+0x2c/0xc0
... ...
[ 89.385566] Call trace:
[ 89.385574] arch_cpu_idle+0x40/0xc0
[ 89.385581] default_idle_call+0x100/0x450
[ 89.385589] cpuidle_idle_call+0x2f8/0x460
[ 89.385596] do_idle+0x1dc/0x3d0
[ 89.385604] cpu_startup_entry+0x5c/0xb0
[ 89.385613] secondary_start_kernel+0x35c/0x520
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The rcu_check_gp_kthread_starvation() function uses task_cpu() to sample
the last CPU that the grace-period kthread ran on, and task_cpu() samples
the thread_info structure's ->cpu field. But this field will always
contain a number corresponding to a CPU that was online some time in
the past, thus never a negative number. This invariant is checked by
a WARN_ON_ONCE() in set_task_cpu().
This means that if the grace-period kthread exists, that is, if the "gpk"
local variable is non-NULL, the "cpu" local variable will be non-negative.
This in turn means that the existing check for non-negative "cpu" is
redundant with the enclosing check for non-NULL "gpk".
This commit threefore removes the redundant check of "cpu".
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Here is the big set of tty and serial driver changes for 6.6-rc1.
Lots of cleanups in here this cycle, and some driver updates. Short
summary is:
- Jiri's continued work to make the tty code and apis be a bit more
sane with regards to modern kernel coding style and types
- cpm_uart driver updates
- n_gsm updates and fixes
- meson driver updates
- sc16is7xx driver updates
- 8250 driver updates for different hardware types
- qcom-geni driver fixes
- tegra serial driver change
- stm32 driver updates
- synclink_gt driver cleanups
- tty structure size reduction
All of these have been in linux-next this week with no reported issues.
The last bit of cleanups from Jiri and the tty structure size reduction
came in last week, a bit late but as they were just style changes and
size reductions, I figured they should get into this merge cycle so that
others can work on top of them with no merge conflicts.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'tty-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty
Pull tty/serial driver updates from Greg KH:
"Here is the big set of tty and serial driver changes for 6.6-rc1.
Lots of cleanups in here this cycle, and some driver updates. Short
summary is:
- Jiri's continued work to make the tty code and apis be a bit more
sane with regards to modern kernel coding style and types
- cpm_uart driver updates
- n_gsm updates and fixes
- meson driver updates
- sc16is7xx driver updates
- 8250 driver updates for different hardware types
- qcom-geni driver fixes
- tegra serial driver change
- stm32 driver updates
- synclink_gt driver cleanups
- tty structure size reduction
All of these have been in linux-next this week with no reported
issues. The last bit of cleanups from Jiri and the tty structure size
reduction came in last week, a bit late but as they were just style
changes and size reductions, I figured they should get into this merge
cycle so that others can work on top of them with no merge conflicts"
* tag 'tty-6.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (199 commits)
tty: shrink the size of struct tty_struct by 40 bytes
tty: n_tty: deduplicate copy code in n_tty_receive_buf_real_raw()
tty: n_tty: extract ECHO_OP processing to a separate function
tty: n_tty: unify counts to size_t
tty: n_tty: use u8 for chars and flags
tty: n_tty: simplify chars_in_buffer()
tty: n_tty: remove unsigned char casts from character constants
tty: n_tty: move newline handling to a separate function
tty: n_tty: move canon handling to a separate function
tty: n_tty: use MASK() for masking out size bits
tty: n_tty: make n_tty_data::num_overrun unsigned
tty: n_tty: use time_is_before_jiffies() in n_tty_receive_overrun()
tty: n_tty: use 'num' for writes' counts
tty: n_tty: use output character directly
tty: n_tty: make flow of n_tty_receive_buf_common() a bool
Revert "tty: serial: meson: Add a earlycon for the T7 SoC"
Documentation: devices.txt: Fix minors for ttyCPM*
Documentation: devices.txt: Remove ttySIOC*
Documentation: devices.txt: Remove ttyIOC*
serial: 8250_bcm7271: improve bcm7271 8250 port
...
Core
----
- Increase size limits for to-be-sent skb frag allocations. This
allows tun, tap devices and packet sockets to better cope with large
writes operations.
- Store netdevs in an xarray, to simplify iterating over netdevs.
- Refactor nexthop selection for multipath routes.
- Improve sched class lifetime handling.
- Add backup nexthop ID support for bridge.
- Implement drop reasons support in openvswitch.
- Several data races annotations and fixes.
- Constify the sk parameter of routing functions.
- Prepend kernel version to netconsole message.
Protocols
---------
- Implement support for TCP probing the peer being under memory
pressure.
- Remove hard coded limitation on IPv6 specific info placement
inside the socket struct.
- Get rid of sysctl_tcp_adv_win_scale and use an auto-estimated
per socket scaling factor.
- Scaling-up the IPv6 expired route GC via a separated list of
expiring routes.
- In-kernel support for the TLS alert protocol.
- Better support for UDP reuseport with connected sockets.
- Add NEXT-C-SID support for SRv6 End.X behavior, reducing the SR
header size.
- Get rid of additional ancillary per MPTCP connection struct socket.
- Implement support for BPF-based MPTCP packet schedulers.
- Format MPTCP subtests selftests results in TAP.
- Several new SMC 2.1 features including unique experimental options,
max connections per lgr negotiation, max links per lgr negotiation.
BPF
---
- Multi-buffer support in AF_XDP.
- Add multi uprobe BPF links for attaching multiple uprobes
and usdt probes, which is significantly faster and saves extra fds.
- Implement an fd-based tc BPF attach API (TCX) and BPF link support on
top of it.
- Add SO_REUSEPORT support for TC bpf_sk_assign.
- Support new instructions from cpu v4 to simplify the generated code and
feature completeness, for x86, arm64, riscv64.
- Support defragmenting IPv(4|6) packets in BPF.
- Teach verifier actual bounds of bpf_get_smp_processor_id()
and fix perf+libbpf issue related to custom section handling.
- Introduce bpf map element count and enable it for all program types.
- Add a BPF hook in sys_socket() to change the protocol ID
from IPPROTO_TCP to IPPROTO_MPTCP to cover migration for legacy.
- Introduce bpf_me_mcache_free_rcu() and fix OOM under stress.
- Add uprobe support for the bpf_get_func_ip helper.
- Check skb ownership against full socket.
- Support for up to 12 arguments in BPF trampoline.
- Extend link_info for kprobe_multi and perf_event links.
Netfilter
---------
- Speed-up process exit by aborting ruleset validation if a
fatal signal is pending.
- Allow NLA_POLICY_MASK to be used with BE16/BE32 types.
Driver API
----------
- Page pool optimizations, to improve data locality and cache usage.
- Introduce ndo_hwtstamp_get() and ndo_hwtstamp_set() to avoid the need
for raw ioctl() handling in drivers.
- Simplify genetlink dump operations (doit/dumpit) providing them
the common information already populated in struct genl_info.
- Extend and use the yaml devlink specs to [re]generate the split ops.
- Introduce devlink selective dumps, to allow SF filtering SF based on
handle and other attributes.
- Add yaml netlink spec for netlink-raw families, allow route, link and
address related queries via the ynl tool.
- Remove phylink legacy mode support.
- Support offload LED blinking to phy.
- Add devlink port function attributes for IPsec.
New hardware / drivers
----------------------
- Ethernet:
- Broadcom ASP 2.0 (72165) ethernet controller
- MediaTek MT7988 SoC
- Texas Instruments AM654 SoC
- Texas Instruments IEP driver
- Atheros qca8081 phy
- Marvell 88Q2110 phy
- NXP TJA1120 phy
- WiFi:
- MediaTek mt7981 support
- Can:
- Kvaser SmartFusion2 PCI Express devices
- Allwinner T113 controllers
- Texas Instruments tcan4552/4553 chips
- Bluetooth:
- Intel Gale Peak
- Qualcomm WCN3988 and WCN7850
- NXP AW693 and IW624
- Mediatek MT2925
Drivers
-------
- Ethernet NICs:
- nVidia/Mellanox:
- mlx5:
- support UDP encapsulation in packet offload mode
- IPsec packet offload support in eswitch mode
- improve aRFS observability by adding new set of counters
- extends MACsec offload support to cover RoCE traffic
- dynamic completion EQs
- mlx4:
- convert to use auxiliary bus instead of custom interface logic
- Intel
- ice:
- implement switchdev bridge offload, even for LAG interfaces
- implement SRIOV support for LAG interfaces
- igc:
- add support for multiple in-flight TX timestamps
- Broadcom:
- bnxt:
- use the unified RX page pool buffers for XDP and non-XDP
- use the NAPI skb allocation cache
- OcteonTX2:
- support Round Robin scheduling HTB offload
- TC flower offload support for SPI field
- Freescale:
- add XDP_TX feature support
- AMD:
- ionic: add support for PCI FLR event
- sfc:
- basic conntrack offload
- introduce eth, ipv4 and ipv6 pedit offloads
- ST Microelectronics:
- stmmac: maximze PTP timestamping resolution
- Virtual NICs:
- Microsoft vNIC:
- batch ringing RX queue doorbell on receiving packets
- add page pool for RX buffers
- Virtio vNIC:
- add per queue interrupt coalescing support
- Google vNIC:
- add queue-page-list mode support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add port range matching tc-flower offload
- permit enslavement to netdevices with uppers
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- convert to phylink_pcs
- Renesas:
- r8A779fx: add speed change support
- rzn1: enables vlan support
- Ethernet PHYs:
- convert mv88e6xxx to phylink_pcs
- WiFi:
- Qualcomm Wi-Fi 7 (ath12k):
- extremely High Throughput (EHT) PHY support
- RealTek (rtl8xxxu):
- enable AP mode for: RTL8192FU, RTL8710BU (RTL8188GU),
RTL8192EU and RTL8723BU
- RealTek (rtw89):
- Introduce Time Averaged SAR (TAS) support
- Connector:
- support for event filtering
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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Merge tag 'net-next-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Paolo Abeni:
"Core:
- Increase size limits for to-be-sent skb frag allocations. This
allows tun, tap devices and packet sockets to better cope with
large writes operations
- Store netdevs in an xarray, to simplify iterating over netdevs
- Refactor nexthop selection for multipath routes
- Improve sched class lifetime handling
- Add backup nexthop ID support for bridge
- Implement drop reasons support in openvswitch
- Several data races annotations and fixes
- Constify the sk parameter of routing functions
- Prepend kernel version to netconsole message
Protocols:
- Implement support for TCP probing the peer being under memory
pressure
- Remove hard coded limitation on IPv6 specific info placement inside
the socket struct
- Get rid of sysctl_tcp_adv_win_scale and use an auto-estimated per
socket scaling factor
- Scaling-up the IPv6 expired route GC via a separated list of
expiring routes
- In-kernel support for the TLS alert protocol
- Better support for UDP reuseport with connected sockets
- Add NEXT-C-SID support for SRv6 End.X behavior, reducing the SR
header size
- Get rid of additional ancillary per MPTCP connection struct socket
- Implement support for BPF-based MPTCP packet schedulers
- Format MPTCP subtests selftests results in TAP
- Several new SMC 2.1 features including unique experimental options,
max connections per lgr negotiation, max links per lgr negotiation
BPF:
- Multi-buffer support in AF_XDP
- Add multi uprobe BPF links for attaching multiple uprobes and usdt
probes, which is significantly faster and saves extra fds
- Implement an fd-based tc BPF attach API (TCX) and BPF link support
on top of it
- Add SO_REUSEPORT support for TC bpf_sk_assign
- Support new instructions from cpu v4 to simplify the generated code
and feature completeness, for x86, arm64, riscv64
- Support defragmenting IPv(4|6) packets in BPF
- Teach verifier actual bounds of bpf_get_smp_processor_id() and fix
perf+libbpf issue related to custom section handling
- Introduce bpf map element count and enable it for all program types
- Add a BPF hook in sys_socket() to change the protocol ID from
IPPROTO_TCP to IPPROTO_MPTCP to cover migration for legacy
- Introduce bpf_me_mcache_free_rcu() and fix OOM under stress
- Add uprobe support for the bpf_get_func_ip helper
- Check skb ownership against full socket
- Support for up to 12 arguments in BPF trampoline
- Extend link_info for kprobe_multi and perf_event links
Netfilter:
- Speed-up process exit by aborting ruleset validation if a fatal
signal is pending
- Allow NLA_POLICY_MASK to be used with BE16/BE32 types
Driver API:
- Page pool optimizations, to improve data locality and cache usage
- Introduce ndo_hwtstamp_get() and ndo_hwtstamp_set() to avoid the
need for raw ioctl() handling in drivers
- Simplify genetlink dump operations (doit/dumpit) providing them the
common information already populated in struct genl_info
- Extend and use the yaml devlink specs to [re]generate the split ops
- Introduce devlink selective dumps, to allow SF filtering SF based
on handle and other attributes
- Add yaml netlink spec for netlink-raw families, allow route, link
and address related queries via the ynl tool
- Remove phylink legacy mode support
- Support offload LED blinking to phy
- Add devlink port function attributes for IPsec
New hardware / drivers:
- Ethernet:
- Broadcom ASP 2.0 (72165) ethernet controller
- MediaTek MT7988 SoC
- Texas Instruments AM654 SoC
- Texas Instruments IEP driver
- Atheros qca8081 phy
- Marvell 88Q2110 phy
- NXP TJA1120 phy
- WiFi:
- MediaTek mt7981 support
- Can:
- Kvaser SmartFusion2 PCI Express devices
- Allwinner T113 controllers
- Texas Instruments tcan4552/4553 chips
- Bluetooth:
- Intel Gale Peak
- Qualcomm WCN3988 and WCN7850
- NXP AW693 and IW624
- Mediatek MT2925
Drivers:
- Ethernet NICs:
- nVidia/Mellanox:
- mlx5:
- support UDP encapsulation in packet offload mode
- IPsec packet offload support in eswitch mode
- improve aRFS observability by adding new set of counters
- extends MACsec offload support to cover RoCE traffic
- dynamic completion EQs
- mlx4:
- convert to use auxiliary bus instead of custom interface
logic
- Intel
- ice:
- implement switchdev bridge offload, even for LAG
interfaces
- implement SRIOV support for LAG interfaces
- igc:
- add support for multiple in-flight TX timestamps
- Broadcom:
- bnxt:
- use the unified RX page pool buffers for XDP and non-XDP
- use the NAPI skb allocation cache
- OcteonTX2:
- support Round Robin scheduling HTB offload
- TC flower offload support for SPI field
- Freescale:
- add XDP_TX feature support
- AMD:
- ionic: add support for PCI FLR event
- sfc:
- basic conntrack offload
- introduce eth, ipv4 and ipv6 pedit offloads
- ST Microelectronics:
- stmmac: maximze PTP timestamping resolution
- Virtual NICs:
- Microsoft vNIC:
- batch ringing RX queue doorbell on receiving packets
- add page pool for RX buffers
- Virtio vNIC:
- add per queue interrupt coalescing support
- Google vNIC:
- add queue-page-list mode support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add port range matching tc-flower offload
- permit enslavement to netdevices with uppers
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- convert to phylink_pcs
- Renesas:
- r8A779fx: add speed change support
- rzn1: enables vlan support
- Ethernet PHYs:
- convert mv88e6xxx to phylink_pcs
- WiFi:
- Qualcomm Wi-Fi 7 (ath12k):
- extremely High Throughput (EHT) PHY support
- RealTek (rtl8xxxu):
- enable AP mode for: RTL8192FU, RTL8710BU (RTL8188GU),
RTL8192EU and RTL8723BU
- RealTek (rtw89):
- Introduce Time Averaged SAR (TAS) support
- Connector:
- support for event filtering"
* tag 'net-next-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1806 commits)
net: ethernet: mtk_wed: minor change in wed_{tx,rx}info_show
net: ethernet: mtk_wed: add some more info in wed_txinfo_show handler
net: stmmac: clarify difference between "interface" and "phy_interface"
r8152: add vendor/device ID pair for D-Link DUB-E250
devlink: move devlink_notify_register/unregister() to dev.c
devlink: move small_ops definition into netlink.c
devlink: move tracepoint definitions into core.c
devlink: push linecard related code into separate file
devlink: push rate related code into separate file
devlink: push trap related code into separate file
devlink: use tracepoint_enabled() helper
devlink: push region related code into separate file
devlink: push param related code into separate file
devlink: push resource related code into separate file
devlink: push dpipe related code into separate file
devlink: move and rename devlink_dpipe_send_and_alloc_skb() helper
devlink: push shared buffer related code into separate file
devlink: push port related code into separate file
devlink: push object register/unregister notifications into separate helpers
inet: fix IP_TRANSPARENT error handling
...
The rcu_nocb_poll kernel boot parameter is defined via early_param(),
whose parsing functions are invoked from parse_early_param() which
is in turn invoked by setup_arch(), which is very early indeed. It
is invoked so early that the console output timestamps read 0.000000,
in other words, before time begins.
This use of early_param() means that the rcu_nocb_poll kernel boot
parameter cannot usefully be embedded into the kernel image. Yes, you
can embed it, but setup_boot_config() is invoked from start_kernel()
too late for it to be parsed.
But it makes no sense to parse this parameter so early. After all,
it cannot do anything until the rcuog kthreads are created, which is
long after rcu_init() time, let alone setup_boot_config() time.
This commit therefore switches the rcu_nocb_poll kernel boot parameter
from early_param() to __setup(), which allows boot-config parsing of
this parameter, in turn allowing it to be embedded into the kernel image.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
The rcu_request_urgent_qs_task() function does a cross-CPU store
to ->rcu_urgent_qs, so this commit therefore marks the load in
__rcu_irq_enter_check_tick() with READ_ONCE().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Now that torture_random() uses swahw32(), its callers no longer see
not-so-random low-order bits, as these are now swapped up into the upper
16 bits of the torture_random() function's return value. This commit
therefore removes the right-shifting of torture_random() return values.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In kernels built with CONFIG_PROVE_RCU=y (for example, lockdep kernels),
the following sequence of events can occur:
o rcu_init_tasks_generic() is invoked just before init is spawned.
It invokes rcu_spawn_tasks_kthread() and friends.
o rcu_spawn_tasks_kthread() invokes rcu_spawn_tasks_kthread_generic(),
which uses kthread_run() to create the needed kthread.
o Control returns to rcu_init_tasks_generic(), which, because this
is a CONFIG_PROVE_RCU=y kernel, invokes the version of the
rcu_tasks_initiate_self_tests() function that actually does
something, including invoking synchronize_rcu_tasks(), which
in turn invokes synchronize_rcu_tasks_generic().
o synchronize_rcu_tasks_generic() sees that the ->kthread_ptr is
still NULL, because the newly spawned kthread has not yet
started.
o The new kthread starts, preempting synchronize_rcu_tasks_generic()
just after its check. This kthread invokes rcu_tasks_one_gp(),
which acquires ->tasks_gp_mutex, and, seeing no work, blocks
in rcuwait_wait_event(). Note that this step requires either
a preemptible kernel or a fault-injection-style sleep at the
beginning of mutex_lock().
o synchronize_rcu_tasks_generic() resumes and invokes rcu_tasks_one_gp().
o rcu_tasks_one_gp() attempts to acquire ->tasks_gp_mutex, which
is still held by the newly spawned kthread's rcu_tasks_one_gp()
function. Deadlock.
Because the only reason for ->tasks_gp_mutex is to handle pre-kthread
synchronous grace periods, this commit avoids this deadlock by having
rcu_tasks_one_gp() momentarily release ->tasks_gp_mutex while invoking
rcuwait_wait_event(). This allows the call to rcu_tasks_one_gp() from
synchronize_rcu_tasks_generic() proceed.
Note that it is not necessary to release the mutex anywhere else in
rcu_tasks_one_gp() because rcuwait_wait_event() is the only function
that can block indefinitely.
Reported-by: Guenter Roeck <linux@roeck-us.net>
Reported-by: Roy Hopkins <rhopkins@suse.de>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Roy Hopkins <rhopkins@suse.de>
Currently, cblist_init_generic() holds a raw spinlock when invoking
INIT_WORK(). This fails in kernels built with CONFIG_DEBUG_OBJECTS=y
due to memory allocation being forbidden while holding a raw spinlock.
But the only reason for holding the raw spinlock is to synchronize
with early boot calls to call_rcu_tasks(), call_rcu_tasks_rude, and,
last but not least, call_rcu_tasks_trace(). These calls also invoke
cblist_init_generic() in order to support early boot queueing of
callbacks.
Except that there are no early boot calls to either of these three
functions, and the BPF guys confirm that they have no plans to add any
such calls.
This commit therefore removes the synchronization and adds a
WARN_ON_ONCE() to catch the case of now-prohibited early boot RCU Tasks
callback queueing.
If early boot queueing is needed, an "initialized" flag may be added to
the rcu_tasks structure. Then queueing a callback before this flag is set
would initialize the callback list (if needed) and queue the callback.
The decision as to where to queue the callback given the possibility of
non-zero boot CPUs is left as an exercise for the reader.
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The passed parameter to sysrq handlers is a key (a character). So change
the type from 'int' to 'u8'. Let it specifically be 'u8' for two
reasons:
* unsigned: unsigned values come from the upper layers (devices) and the
tty layer assumes unsigned on most places, and
* 8-bit: as that what's supposed to be one day in all the layers built
on the top of tty. (Currently, we use mostly 'unsigned char' and
somewhere still only 'char'. (But that also translates to the former
thanks to -funsigned-char.))
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Len Brown <len.brown@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Zqiang <qiang.zhang1211@gmail.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de> # DRM
Acked-by: WANG Xuerui <git@xen0n.name> # loongarch
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20230712081811.29004-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Make it clear that this function always returns either true or false
without other planned failure modes.
Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
The rtort_pipe_count WARN() indicates that grace periods were unable
to invoke all callbacks during a stutter_wait() interval. But it is
sometimes helpful to have a bit more information as to why. This commit
therefore invokes show_rcu_gp_kthreads() immediately before that WARN()
in order to dump out some relevant information.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Both the CONFIG_TASKS_RCU and CONFIG_TASKS_RUDE_RCU options
are broken when RCU_TINY is enabled as well, as some functions
are missing a declaration.
In file included from kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1271:21: error: no previous prototype for 'get_rcu_tasks_rude_gp_kthread' [-Werror=missing-prototypes]
1271 | struct task_struct *get_rcu_tasks_rude_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/rcu/rcuscale.c:330:27: error: 'get_rcu_tasks_rude_gp_kthread' undeclared here (not in a function); did you mean 'get_rcu_tasks_trace_gp_kthread'?
330 | .rso_gp_kthread = get_rcu_tasks_rude_gp_kthread,
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| get_rcu_tasks_trace_gp_kthread
In file included from /home/arnd/arm-soc/kernel/rcu/update.c:649:
kernel/rcu/tasks.h:1113:21: error: no previous prototype for 'get_rcu_tasks_gp_kthread' [-Werror=missing-prototypes]
1113 | struct task_struct *get_rcu_tasks_gp_kthread(void)
| ^~~~~~~~~~~~~~~~~~~~~~~~
Also, building with CONFIG_TASKS_RUDE_RCU but not CONFIG_TASKS_RCU is
broken because of some missing stub functions:
kernel/rcu/rcuscale.c:322:27: error: 'tasks_scale_read_lock' undeclared here (not in a function); did you mean 'srcu_scale_read_lock'?
322 | .readlock = tasks_scale_read_lock,
| ^~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_lock
kernel/rcu/rcuscale.c:323:27: error: 'tasks_scale_read_unlock' undeclared here (not in a function); did you mean 'srcu_scale_read_unlock'?
323 | .readunlock = tasks_scale_read_unlock,
| ^~~~~~~~~~~~~~~~~~~~~~~
| srcu_scale_read_unlock
Move the declarations outside of the RCU_TINY #ifdef and duplicate the
shared stub functions to address all of the above.
Fixes: 88d7ff818f0ce ("rcuscale: Add RCU Tasks Rude testing")
Fixes: 755f1c5eb416b ("rcuscale: Measure RCU Tasks Trace grace-period kthread CPU time")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit causes RCU Tasks Trace to output the CPU time consumed by
its grace-period kthread. The CPU time is whatever is in the designated
task's current->stime field, and thus is controlled by whatever CPU-time
accounting scheme is in effect.
This output appears in microseconds as follows on the console:
rcu_scale: Grace-period kthread CPU time: 42367.037
[ paulmck: Apply Willy Tarreau feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the ability to output the CPU time consumed by the
grace-period kthread for the RCU variant under test. The CPU time is
whatever is in the designated task's current->stime field, and thus is
controlled by whatever CPU-time accounting scheme is in effect.
This output appears in microseconds as follows on the console:
rcu_scale: Grace-period kthread CPU time: 42367.037
[ paulmck: Apply feedback from Stephen Rothwell and kernel test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
By default, rcuscale collects only 100 points of data per writer, but
arranging for all kthreads to be actively collecting (if not recording)
data during the time that any kthread might be recording. This works
well, but does not allow much time to bring external performance tools
to bear. This commit therefore adds a minruntime module parameter
that specifies a minimum data-collection interval in seconds.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Some workloads do isolated RCU work, and this can affect operation
latencies. This commit therefore adds a writer_holdoff_jiffies module
parameter that causes writers to block for the specified number of
jiffies between each pair of consecutive write-side operations.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a "jiffies" test to refscale, allowing use of jiffies
to be compared to ktime_get_real_fast_ns(). On my x86 laptop, jiffies
is more than 20x faster. (Though for many uses, the tens-of-nanoseconds
overhead of ktime_get_real_fast_ns() will be just fine.)
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Running the refscale test occasionally crashes the kernel with the
following error:
[ 8569.952896] BUG: unable to handle page fault for address: ffffffffffffffe8
[ 8569.952900] #PF: supervisor read access in kernel mode
[ 8569.952902] #PF: error_code(0x0000) - not-present page
[ 8569.952904] PGD c4b048067 P4D c4b049067 PUD c4b04b067 PMD 0
[ 8569.952910] Oops: 0000 [#1] PREEMPT_RT SMP NOPTI
[ 8569.952916] Hardware name: Dell Inc. PowerEdge R750/0WMWCR, BIOS 1.2.4 05/28/2021
[ 8569.952917] RIP: 0010:prepare_to_wait_event+0x101/0x190
:
[ 8569.952940] Call Trace:
[ 8569.952941] <TASK>
[ 8569.952944] ref_scale_reader+0x380/0x4a0 [refscale]
[ 8569.952959] kthread+0x10e/0x130
[ 8569.952966] ret_from_fork+0x1f/0x30
[ 8569.952973] </TASK>
The likely cause is that init_waitqueue_head() is called after the call to
the torture_create_kthread() function that creates the ref_scale_reader
kthread. Although this init_waitqueue_head() call will very likely
complete before this kthread is created and starts running, it is
possible that the calling kthread will be delayed between the calls to
torture_create_kthread() and init_waitqueue_head(). In this case, the
new kthread will use the waitqueue head before it is properly initialized,
which is not good for the kernel's health and well-being.
The above crash happened here:
static inline void __add_wait_queue(...)
{
:
if (!(wq->flags & WQ_FLAG_PRIORITY)) <=== Crash here
The offset of flags from list_head entry in wait_queue_entry is
-0x18. If reader_tasks[i].wq.head.next is NULL as allocated reader_task
structure is zero initialized, the instruction will try to access address
0xffffffffffffffe8, which is exactly the fault address listed above.
This commit therefore invokes init_waitqueue_head() before creating
the kthread.
Fixes: 653ed64b01 ("refperf: Add a test to measure performance of read-side synchronization")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The various RCU Tasks flavors now do lazy grace periods when there are
only asynchronous grace period requests. By default, the system will let
250 milliseconds elapse after the first call_rcu_tasks*() callbacki is
queued before starting a grace period. In contrast, synchronous grace
period requests such as synchronize_rcu_tasks*() will start a grace
period immediately.
However, invoking one of the call_rcu_tasks*() functions in a too-tight
loop can result in a callback flood, which in turn can exhaust memory
if grace periods are delayed for too long.
This commit therefore sets a limit so that the grace-period kthread
will be awakened when any CPU's callback list expands to contain
rcupdate.rcu_task_lazy_lim callbacks elements (defaulting to 32, set to -1
to disable), the grace-period kthread will be awakened, thus cancelling
any ongoing laziness and getting out in front of the potential callback
flood.
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds kernel boot parameters for callback laziness, allowing
the RCU Tasks flavors to be individually adjusted.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The performance requirements on RCU Tasks, and in particular on RCU
Tasks Trace, have evolved over time as the workloads have evolved.
The current implementation is designed to provide low grace-period
latencies, and also to accommodate short-duration floods of callbacks.
However, current workloads can also provide a constant background
callback-queuing rate of a few hundred call_rcu_tasks_trace() invocations
per second. This results in continuous back-to-back RCU Tasks Trace
grace periods, which in turn can consume the better part of 10% of a CPU.
One could take the attitude that there are several tens of other CPUs on
the systems running such workloads, but energy efficiency is a thing.
On these systems, although asynchronous grace-period requests happen
every few milliseconds, synchronous grace-period requests are quite rare.
This commit therefore arrranges for grace periods to be initiated
immediately in response to calls to synchronize_rcu_tasks*() and
also to calls to synchronize_rcu_mult() that are passed one of the
call_rcu_tasks*() functions. These are recognized by the tell-tale
wakeme_after_rcu callback function.
In other cases, callbacks are gathered up for up to about 250 milliseconds
before a grace period is initiated. This results in more than an order of
magnitude reduction in RCU Tasks Trace grace periods, with corresponding
reduction in consumption of CPU time.
Reported-by: Alexei Starovoitov <ast@kernel.org>
Reported-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If a CPU is executing a long series of non-sleeping system calls,
RCU grace periods can be delayed for on the order of a couple hundred
milliseconds. This is normally not a problem, but if each system call
does a call_rcu(), those callbacks can stack up. RCU will eventually
notice this callback storm, but use of rcu_request_urgent_qs_task()
allows the code invoking call_rcu() to give RCU a heads up.
This function is not for general use, not yet, anyway.
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230706033447.54696-11-alexei.starovoitov@gmail.com
This code-movement-only commit moves the rcu_scale_cleanup() and
rcu_scale_shutdown() functions to follow kfree_scale_cleanup().
This is code movement is in preparation for a bug-fix patch that invokes
kfree_scale_cleanup() from rcu_scale_cleanup().
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Callbacks can only be queued as lazy on NOCB CPUs, therefore iterating
over the NOCB mask is enough for both counting and scanning. Just lock
the mostly uncontended barrier mutex on counting as well in order to
keep rcu_nocb_mask stable.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_tasks_invoke_cbs() function relies on queue_work_on() to silently
fall back to WORK_CPU_UNBOUND when the specified CPU is offline. However,
the queue_work_on() function's silent fallback mechanism relies on that
CPU having been online at some time in the past. When queue_work_on()
is passed a CPU that has never been online, workqueue lockups ensue,
which can be bad for your kernel's general health and well-being.
This commit therefore checks whether a given CPU has ever been online,
and, if not substitutes WORK_CPU_UNBOUND in the subsequent call to
queue_work_on(). Why not simply omit the queue_work_on() call entirely?
Because this function is flooding callback-invocation notifications
to all CPUs, and must deal with possibilities that include a sparse
cpu_possible_mask.
This commit also moves the setting of the rcu_data structure's
->beenonline field to rcu_cpu_starting(), which executes on the
incoming CPU before that CPU has ever enabled interrupts. This ensures
that the required workqueues are present. In addition, because the
incoming CPU has not yet enabled its interrupts, there cannot yet have
been any softirq handlers running on this CPU, which means that the
WARN_ON_ONCE(!rdp->beenonline) within the RCU_SOFTIRQ handler cannot
have triggered yet.
Fixes: d363f833c6 ("rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations")
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, rcu_cpu_starting() is written so that it might be invoked
with interrupts enabled. However, it is always called when interrupts
are disabled, either by rcu_init(), notify_cpu_starting(), or from a
call point prior to the call to notify_cpu_starting().
But why bother requiring that interrupts be disabled? The purpose is
to allow the rcu_data structure's ->beenonline flag to be set after all
early processing has completed for the incoming CPU, thus allowing this
flag to be used to determine when workqueues have been set up for the
incoming CPU, while still allowing this flag to be used as a diagnostic
within rcu_core().
This commit therefore makes rcu_cpu_starting() rely on interrupts being
disabled.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_data structure's ->rcu_cpu_has_work field can be modified by
any CPU attempting to wake up the rcuc kthread. Therefore, this commit
marks accesses to this field from the rcu_cpu_kthread() function.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The per-CPU rcu_data structure's ->cpu_no_qs.b.exp field is updated
only on the instance corresponding to the current CPU, but can be read
more widely. Unmarked accesses are OK from the corresponding CPU, but
only if interrupts are disabled, given that interrupt handlers can and
do modify this field.
Unfortunately, although the load from rcu_preempt_deferred_qs() is always
carried out from the corresponding CPU, interrupts are not necessarily
disabled. This commit therefore upgrades this load to READ_ONCE.
Similarly, the diagnostic access from synchronize_rcu_expedited_wait()
might run with interrupts disabled and from some other CPU. This commit
therefore marks this load with data_race().
Finally, the C-language access in rcu_preempt_ctxt_queue() is OK as
is because interrupts are disabled and this load is always from the
corresponding CPU. This commit adds a comment giving the rationale for
this access being safe.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, if there are more than 100 ready-to-invoke RCU callbacks queued
on a given CPU, the rcu_do_batch() function sets a timeout for invocation
of the series. This timeout defaulting to three milliseconds, and may
be adjusted using the rcutree.rcu_resched_ns kernel boot parameter.
This timeout is checked using local_clock(), but the overhead of this
function combined with the common-case very small callback-invocation
overhead means that local_clock() is checked every 32nd invocation.
This works well except for longer-than average callbacks. For example,
a series of 500-microsecond-duration callbacks means that local_clock()
is checked only once every 16 milliseconds, which makes it difficult to
enforce a three-millisecond timeout.
This commit therefore adds a Kconfig option RCU_DOUBLE_CHECK_CB_TIME
that enables backup timeout checking using the coarser grained but
lighter weight jiffies. If the jiffies counter detects a timeout,
then local_clock() is consulted even if this is not the 32nd callback.
This prevents the aforementioned 16-millisecond latency blow.
Reported-by: Domas Mituzas <dmituzas@meta.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, a callback-invocation time limit is enforced only for
callbacks invoked from the softirq environment, the rationale being
that when callbacks are instead invoked from rcuc and rcuoc kthreads,
these callbacks cannot be holding up other softirq vectors.
Which is in fact true. However, if an rcuc kthread spends too much time
invoking callbacks, it can delay quiescent-state reports from its CPU,
which can also be a problem.
This commit therefore applies the callback-invocation time limit to
callback invocation from the rcuc kthreads as well as from softirq.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit uses rtp->name instead of __func__ and outputs the value
of rcu_task_cb_adjust, thus reducing console-log output.
Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The ->lazy_len is only checked locklessly. Recheck again under the
->nocb_lock to avoid spending more time on flushing/waking if not
necessary. The ->lazy_len can still increment concurrently (from 1 to
infinity) but under the ->nocb_lock we at least know for sure if there
are lazy callbacks at all (->lazy_len > 0).
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The shrinker resets the lazy callbacks counter in order to trigger the
pending lazy queue flush though the rcuog kthread. The counter reset is
protected by the ->nocb_lock against concurrent accesses...except
for one of them. Here is a list of existing synchronized readers/writer:
1) The first lazy enqueuer (incrementing ->lazy_len to 1) does so under
->nocb_lock and ->nocb_bypass_lock.
2) The further lazy enqueuers (incrementing ->lazy_len above 1) do so
under ->nocb_bypass_lock _only_.
3) The lazy flush checks and resets to 0 under ->nocb_lock and
->nocb_bypass_lock.
The shrinker protects its ->lazy_len reset against cases 1) and 3) but
not against 2). As such, setting ->lazy_len to 0 under the ->nocb_lock
may be cancelled right away by an overwrite from an enqueuer, leading
rcuog to ignore the flush.
To avoid that, use the proper bypass flush API which takes care of all
those details.
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Frederic Weisbecker