locking/semaphore: Use wake_q to wake up processes outside lock critical section

A circular lock dependency splat has been seen involving down_trylock():

=========================================

locking/semaphore: Use wake_q to wake up processes outside lock critical section

A circular lock dependency splat has been seen involving down_trylock():

======================================================
WARNING: possible circular locking dependency detected
6.12.0-41.el10.s390x+debug
------------------------------------------------------
dd/32479 is trying to acquire lock:
0015a20accd0d4f8 ((console_sem).lock){-.-.}-{2:2}, at: down_trylock+0x26/0x90

but task is already holding lock:
000000017e461698 (&zone->lock){-.-.}-{2:2}, at: rmqueue_bulk+0xac/0x8f0

the existing dependency chain (in reverse order) is:
-> #4 (&zone->lock){-.-.}-{2:2}:
-> #3 (hrtimer_bases.lock){-.-.}-{2:2}:
-> #2 (&rq->__lock){-.-.}-{2:2}:
-> #1 (&p->pi_lock){-.-.}-{2:2}:
-> #0 ((console_sem).lock){-.-.}-{2:2}:

The console_sem -> pi_lock dependency is due to calling try_to_wake_up()
while holding the console_sem raw_spinlock. This dependency can be broken
by using wake_q to do the wakeup instead of calling try_to_wake_up()
under the console_sem lock. This will also make the semaphore's
raw_spinlock become a terminal lock without taking any further locks
underneath it.

The hrtimer_bases.lock is a raw_spinlock while zone->lock is a
spinlock. The hrtimer_bases.lock -> zone->lock dependency happens via
the debug_objects_fill_pool() helper function in the debugobjects code.

-> #4 (&zone->lock){-.-.}-{2:2}:
__lock_acquire+0xe86/0x1cc0
lock_acquire.part.0+0x258/0x630
lock_acquire+0xb8/0xe0
_raw_spin_lock_irqsave+0xb4/0x120
rmqueue_bulk+0xac/0x8f0
__rmqueue_pcplist+0x580/0x830
rmqueue_pcplist+0xfc/0x470
rmqueue.isra.0+0xdec/0x11b0
get_page_from_freelist+0x2ee/0xeb0
__alloc_pages_noprof+0x2c2/0x520
alloc_pages_mpol_noprof+0x1fc/0x4d0
alloc_pages_noprof+0x8c/0xe0
allocate_slab+0x320/0x460
___slab_alloc+0xa58/0x12b0
__slab_alloc.isra.0+0x42/0x60
kmem_cache_alloc_noprof+0x304/0x350
fill_pool+0xf6/0x450
debug_object_activate+0xfe/0x360
enqueue_hrtimer+0x34/0x190
__run_hrtimer+0x3c8/0x4c0
__hrtimer_run_queues+0x1b2/0x260
hrtimer_interrupt+0x316/0x760
do_IRQ+0x9a/0xe0
do_irq_async+0xf6/0x160

Normally a raw_spinlock to spinlock dependency is not legitimate
and will be warned if CONFIG_PROVE_RAW_LOCK_NESTING is enabled,
but debug_objects_fill_pool() is an exception as it explicitly
allows this dependency for non-PREEMPT_RT kernel without causing
PROVE_RAW_LOCK_NESTING lockdep splat. As a result, this dependency is
legitimate and not a bug.

Anyway, semaphore is the only locking primitive left that is still
using try_to_wake_up() to do wakeup inside critical section, all the
other locking primitives had been migrated to use wake_q to do wakeup
outside of the critical section. It is also possible that there are
other circular locking dependencies involving printk/console_sem or
other existing/new semaphores lurking somewhere which may show up in
the future. Let just do the migration now to wake_q to avoid headache
like this.

Reported-by: [email protected]
Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Boqun Feng <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

locking: Add __sched to semaphore functions

The internal functions are marked with __sched already, let's do the same
for external functions too so that we can skip them in the stack trace.

Signed-

locking: Add __sched to semaphore functions

The internal functions are marked with __sched already, let's do the same
for external functions too so that we can skip them in the stack trace.

Signed-off-by: Namhyung Kim <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

locking: Apply contention tracepoints in the slow path

Adding the lock contention tracepoints in various lock function slow
paths. Note that each arch can define spinlock differently, I only
added

locking: Apply contention tracepoints in the slow path

Adding the lock contention tracepoints in various lock function slow
paths. Note that each arch can define spinlock differently, I only
added it only to the generic qspinlock for now.

Signed-off-by: Namhyung Kim <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Hyeonggon Yoo <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

show more ...

locking/semaphore: Add might_sleep() to down_*() family

Semaphore is sleeping lock. Add might_sleep() to down*() family
(with exception of down_trylock()) to detect atomic context sleep.

Signed-off

locking/semaphore: Add might_sleep() to down_*() family

Semaphore is sleeping lock. Add might_sleep() to down*() family
(with exception of down_trylock()) to detect atomic context sleep.

Signed-off-by: Xiaoming Ni <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

show more ...

kernel: delete repeated words in comments

Drop repeated words in kernel/events/.
{if, the, that, with, time}

Drop repeated words in kernel/locking/.
{it, no, the}

Drop repeated words in kernel/sch

kernel: delete repeated words in comments

Drop repeated words in kernel/events/.
{if, the, that, with, time}

Drop repeated words in kernel/locking/.
{it, no, the}

Drop repeated words in kernel/sched/.
{in, not}

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Randy Dunlap <[email protected]>
Acked-by: Will Deacon <[email protected]> [kernel/locking/]
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Juri Lelli <[email protected]>
Cc: Vincent Guittot <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

show more ...

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 436

Based on 1 normalized pattern(s):

distributed under the terms of the gnu gpl version 2

extracted by the scancode license scanne

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 436

Based on 1 normalized pattern(s):

distributed under the terms of the gnu gpl version 2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 2 file(s).

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Armijn Hemel <[email protected]>
Reviewed-by: Allison Randal <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

show more ...

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up fro

sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>

We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/debug.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.

Acked-by: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

sched/core: Remove set_task_state()

This is a nasty interface and setting the state of a foreign task must
not be done. As of the following commit:

be628be0956 ("bcache: Make gc wakeup sane, remo

sched/core: Remove set_task_state()

This is a nasty interface and setting the state of a foreign task must
not be done. As of the following commit:

be628be0956 ("bcache: Make gc wakeup sane, remove set_task_state()")

... everyone in the kernel calls set_task_state() with current, allowing
the helper to be removed.

However, as the comment indicates, it is still around for those archs
where computing current is more expensive than using a pointer, at least
in theory. An important arch that is affected is arm64, however this has
been addressed now [1] and performance is up to par making no difference
with either calls.

Of all the callers, if any, it's the locking bits that would care most
about this -- ie: we end up passing a tsk pointer to a lot of the lock
slowpath, and setting ->state on that. The following numbers are based
on two tests: a custom ad-hoc microbenchmark that just measures
latencies (for ~65 million calls) between get_task_state() vs
get_current_state().

Secondly for a higher overview, an unlink microbenchmark was used,
which pounds on a single file with open, close,unlink combos with
increasing thread counts (up to 4x ncpus). While the workload is quite
unrealistic, it does contend a lot on the inode mutex or now rwsem.

[1] https://lkml.kernel.org/r/[email protected]

== 1. x86-64 ==

Avg runtime set_task_state(): 601 msecs
Avg runtime set_current_state(): 552 msecs

vanilla dirty
Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%)
Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%)
Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%)
Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%)
Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%)
Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%)
Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%)
Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%)
Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%)
Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%)
Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%)
Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%)
Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%)

== 2. ppc64le ==

Avg runtime set_task_state(): 938 msecs
Avg runtime set_current_state: 940 msecs

vanilla dirty
Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%)
Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%)
Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%)
Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%)
Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%)
Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%)
Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%)
Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%)
Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%)
Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%)
Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%)
Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%)
Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%)
Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%)
Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%)
Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%)

x86-64 (known to be fast for get_current()/this_cpu_read_stable() caching)
and ppc64 (with paca) show similar improvements in the unlink microbenches.
The small delta for ppc64 (2ms), does not represent the gains on the unlink
runs. In the case of x86, there was a decent amount of variation in the
latency runs, but always within a 20 to 50ms increase), ppc was more constant.

Signed-off-by: Davidlohr Bueso <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

kernel/locking: Compute 'current' directly

This patch effectively replaces the tsk pointer dereference
(which is obviously == current), to directly use get_current()
macro. This is to make the remov

kernel/locking: Compute 'current' directly

This patch effectively replaces the tsk pointer dereference
(which is obviously == current), to directly use get_current()
macro. This is to make the removal of setting foreign task
states smoother and painfully obvious. Performance win on some
archs such as x86-64 and ppc64. On a microbenchmark that calls
set_task_state() vs set_current_state() and an inode rwsem
pounding benchmark doing unlink:

== 1. x86-64 ==

Avg runtime set_task_state(): 601 msecs
Avg runtime set_current_state(): 552 msecs

vanilla dirty
Hmean unlink1-processes-2 36089.26 ( 0.00%) 38977.33 ( 8.00%)
Hmean unlink1-processes-5 28555.01 ( 0.00%) 29832.55 ( 4.28%)
Hmean unlink1-processes-8 37323.75 ( 0.00%) 44974.57 ( 20.50%)
Hmean unlink1-processes-12 43571.88 ( 0.00%) 44283.01 ( 1.63%)
Hmean unlink1-processes-21 34431.52 ( 0.00%) 38284.45 ( 11.19%)
Hmean unlink1-processes-30 34813.26 ( 0.00%) 37975.17 ( 9.08%)
Hmean unlink1-processes-48 37048.90 ( 0.00%) 39862.78 ( 7.59%)
Hmean unlink1-processes-79 35630.01 ( 0.00%) 36855.30 ( 3.44%)
Hmean unlink1-processes-110 36115.85 ( 0.00%) 39843.91 ( 10.32%)
Hmean unlink1-processes-141 32546.96 ( 0.00%) 35418.52 ( 8.82%)
Hmean unlink1-processes-172 34674.79 ( 0.00%) 36899.21 ( 6.42%)
Hmean unlink1-processes-203 37303.11 ( 0.00%) 36393.04 ( -2.44%)
Hmean unlink1-processes-224 35712.13 ( 0.00%) 36685.96 ( 2.73%)

== 2. ppc64le ==

Avg runtime set_task_state(): 938 msecs
Avg runtime set_current_state: 940 msecs

vanilla dirty
Hmean unlink1-processes-2 19269.19 ( 0.00%) 30704.50 ( 59.35%)
Hmean unlink1-processes-5 20106.15 ( 0.00%) 21804.15 ( 8.45%)
Hmean unlink1-processes-8 17496.97 ( 0.00%) 17243.28 ( -1.45%)
Hmean unlink1-processes-12 14224.15 ( 0.00%) 17240.21 ( 21.20%)
Hmean unlink1-processes-21 14155.66 ( 0.00%) 15681.23 ( 10.78%)
Hmean unlink1-processes-30 14450.70 ( 0.00%) 15995.83 ( 10.69%)
Hmean unlink1-processes-48 16945.57 ( 0.00%) 16370.42 ( -3.39%)
Hmean unlink1-processes-79 15788.39 ( 0.00%) 14639.27 ( -7.28%)
Hmean unlink1-processes-110 14268.48 ( 0.00%) 14377.40 ( 0.76%)
Hmean unlink1-processes-141 14023.65 ( 0.00%) 16271.69 ( 16.03%)
Hmean unlink1-processes-172 13417.62 ( 0.00%) 16067.55 ( 19.75%)
Hmean unlink1-processes-203 15293.08 ( 0.00%) 15440.40 ( 0.96%)
Hmean unlink1-processes-234 13719.32 ( 0.00%) 16190.74 ( 18.01%)
Hmean unlink1-processes-265 16400.97 ( 0.00%) 16115.22 ( -1.74%)
Hmean unlink1-processes-296 14388.60 ( 0.00%) 16216.13 ( 12.70%)
Hmean unlink1-processes-320 15771.85 ( 0.00%) 15905.96 ( 0.85%)

Signed-off-by: Davidlohr Bueso <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

locking/semaphore: Resolve some shadow warnings

Resolve some shadow warnings resulting from using the name
jiffies, which is a well-known global. This is not a problem
of course, but it could be a t

locking/semaphore: Resolve some shadow warnings

Resolve some shadow warnings resulting from using the name
jiffies, which is a well-known global. This is not a problem
of course, but it could be a trap for someone copying and
pasting code, and it just makes W=2 a little cleaner.

Signed-off-by: Mark Rustad <[email protected]>
Signed-off-by: Jeff Kirsher <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...

locking: Move the semaphore core to kernel/locking/

Suggested-by: Ingo Molnar <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/n/tip-vmw5sf6vzmua1

locking: Move the semaphore core to kernel/locking/

Suggested-by: Ingo Molnar <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

show more ...