linux-stable.git/kernel/sched/core.c, branch linux-5.11.y Linux kernel stable tree sched: Fix out-of-bound access in uclamp 2021-05-19T08:29:47+00:00 Quentin Perret qperret@google.com 2021-04-30T15:14:12+00:00 3da3f804b82a0a382d523a21acf4cf3bb35f936d [ Upstream commit 6d2f8909a5fabb73fe2a63918117943986c39b6c ] Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Clamp the bucket id to fix the issue. Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") Suggested-by: Qais Yousef <qais.yousef@arm.com> Signed-off-by: Quentin Perret <qperret@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@google.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 6d2f8909a5fabb73fe2a63918117943986c39b6c ]

Util-clamp places tasks in different buckets based on their clamp values
for performance reasons. However, the size of buckets is currently
computed using a rounding division, which can lead to an off-by-one
error in some configurations.

For instance, with 20 buckets, the bucket size will be 1024/20=51. A
task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly,
correct indexes are in range [0,19], hence leading to an out of bound
memory access.

Clamp the bucket id to fix the issue.

Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting")
Suggested-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lkml.kernel.org/r/20210430151412.160913-1-qperret@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
kthread: Fix PF_KTHREAD vs to_kthread() race 2021-05-14T08:49:59+00:00 Peter Zijlstra peterz@infradead.org 2021-04-20T08:18:17+00:00 42e4caa93282ade6a143ff320d71062874dd3a5a [ Upstream commit 3a7956e25e1d7b3c148569e78895e1f3178122a9 ] The kthread_is_per_cpu() construct relies on only being called on PF_KTHREAD tasks (per the WARN in to_kthread). This gives rise to the following usage pattern: if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p)) However, as reported by syzcaller, this is broken. The scenario is: CPU0 CPU1 (running p) (p->flags & PF_KTHREAD) // true begin_new_exec() me->flags &= ~(PF_KTHREAD|...); kthread_is_per_cpu(p) to_kthread(p) WARN(!(p->flags & PF_KTHREAD) <-- *SPLAT* Introduce __to_kthread() that omits the WARN and is sure to check both values. Use this to remove the problematic pattern for kthread_is_per_cpu() and fix a number of other kthread_*() functions that have similar issues but are currently not used in ways that would expose the problem. Notably kthread_func() is only ever called on 'current', while kthread_probe_data() is only used for PF_WQ_WORKER, which implies the task is from kthread_create*(). Fixes: ac687e6e8c26 ("kthread: Extract KTHREAD_IS_PER_CPU") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com> Link: https://lkml.kernel.org/r/YH6WJc825C4P0FCK@hirez.programming.kicks-ass.net Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3a7956e25e1d7b3c148569e78895e1f3178122a9 ]

The kthread_is_per_cpu() construct relies on only being called on
PF_KTHREAD tasks (per the WARN in to_kthread). This gives rise to the
following usage pattern:

	if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p))

However, as reported by syzcaller, this is broken. The scenario is:

	CPU0				CPU1 (running p)

	(p->flags & PF_KTHREAD) // true

					begin_new_exec()
					  me->flags &= ~(PF_KTHREAD|...);
	kthread_is_per_cpu(p)
	  to_kthread(p)
	    WARN(!(p->flags & PF_KTHREAD) <-- *SPLAT*

Introduce __to_kthread() that omits the WARN and is sure to check both
values.

Use this to remove the problematic pattern for kthread_is_per_cpu()
and fix a number of other kthread_*() functions that have similar
issues but are currently not used in ways that would expose the
problem.

Notably kthread_func() is only ever called on 'current', while
kthread_probe_data() is only used for PF_WQ_WORKER, which implies the
task is from kthread_create*().

Fixes: ac687e6e8c26 ("kthread: Extract KTHREAD_IS_PER_CPU")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <Valentin.Schneider@arm.com>
Link: https://lkml.kernel.org/r/YH6WJc825C4P0FCK@hirez.programming.kicks-ass.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched: Simplify set_affinity_pending refcounts 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-24T10:42:08+00:00 ab4728011789c84a6bca3c3a88ea8ace7acec837 commit 50caf9c14b1498c90cf808dbba2ca29bd32ccba4 upstream. Now that we have set_affinity_pending::stop_pending to indicate if a stopper is in progress, and we have the guarantee that if that stopper exists, it will (eventually) complete our @pending we can simplify the refcount scheme by no longer counting the stopper thread. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.724130207@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 50caf9c14b1498c90cf808dbba2ca29bd32ccba4 upstream.

Now that we have set_affinity_pending::stop_pending to indicate if a
stopper is in progress, and we have the guarantee that if that stopper
exists, it will (eventually) complete our @pending we can simplify the
refcount scheme by no longer counting the stopper thread.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.724130207@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Fix affine_move_task() self-concurrency 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-24T10:31:09+00:00 6ebb2dbadb442e8efb4b7a5daa4a50031b2a8491 commit 9e81889c7648d48dd5fe13f41cbc99f3c362484a upstream. Consider: sched_setaffinity(p, X); sched_setaffinity(p, Y); Then the first will install p->migration_pending = &my_pending; and issue stop_one_cpu_nowait(pending); and the second one will read p->migration_pending and _also_ issue: stop_one_cpu_nowait(pending), the _SAME_ @pending. This causes stopper list corruption. Add set_affinity_pending::stop_pending, to indicate if a stopper is in progress. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.649146419@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 9e81889c7648d48dd5fe13f41cbc99f3c362484a upstream.

Consider:

   sched_setaffinity(p, X);		sched_setaffinity(p, Y);

Then the first will install p->migration_pending = &my_pending; and
issue stop_one_cpu_nowait(pending); and the second one will read
p->migration_pending and _also_ issue: stop_one_cpu_nowait(pending),
the _SAME_ @pending.

This causes stopper list corruption.

Add set_affinity_pending::stop_pending, to indicate if a stopper is in
progress.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.649146419@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Optimize migration_cpu_stop() 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-24T10:21:35+00:00 a8957bc5a1a086fc806a6441c9157f12e6ef7129 commit 3f1bc119cd7fc987c8ed25ffb717f99403bb308c upstream. When the purpose of migration_cpu_stop() is to migrate the task to 'any' valid CPU, don't migrate the task when it's already running on a valid CPU. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 3f1bc119cd7fc987c8ed25ffb717f99403bb308c upstream.

When the purpose of migration_cpu_stop() is to migrate the task to
'any' valid CPU, don't migrate the task when it's already running on a
valid CPU.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.569238629@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Simplify migration_cpu_stop() 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-24T10:50:39+00:00 dd8b56e25964452c63eb01ce49b9e4cfd97c4dc0 commit c20cf065d4a619d394d23290093b1002e27dff86 upstream. When affine_move_task() issues a migration_cpu_stop(), the purpose of that function is to complete that @pending, not any random other p->migration_pending that might have gotten installed since. This realization much simplifies migration_cpu_stop() and allows further necessary steps to fix all this as it provides the guarantee that @pending's stopper will complete @pending (and not some random other @pending). Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.430014682@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit c20cf065d4a619d394d23290093b1002e27dff86 upstream.

When affine_move_task() issues a migration_cpu_stop(), the purpose of
that function is to complete that @pending, not any random other
p->migration_pending that might have gotten installed since.

This realization much simplifies migration_cpu_stop() and allows
further necessary steps to fix all this as it provides the guarantee
that @pending's stopper will complete @pending (and not some random
other @pending).

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.430014682@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Collate affine_move_task() stoppers 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-24T10:15:23+00:00 3d0fef8ad71809778aeb4e43599ae5ec1d5428c9 commit 58b1a45086b5f80f2b2842aa7ed0da51a64a302b upstream. The SCA_MIGRATE_ENABLE and task_running() cases are almost identical, collapse them to avoid further duplication. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.500108964@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 58b1a45086b5f80f2b2842aa7ed0da51a64a302b upstream.

The SCA_MIGRATE_ENABLE and task_running() cases are almost identical,
collapse them to avoid further duplication.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.500108964@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Fix migration_cpu_stop() requeueing 2021-03-17T16:11:44+00:00 Peter Zijlstra peterz@infradead.org 2021-02-13T12:10:35+00:00 5b4f39edf62bad6e59fd9083e92667edd74fb964 commit 8a6edb5257e2a84720fe78cb179eca58ba76126f upstream. When affine_move_task(p) is called on a running task @p, which is not otherwise already changing affinity, we'll first set p->migration_pending and then do: stop_one_cpu(cpu_of_rq(rq), migration_cpu_stop, &arg); This then gets us to migration_cpu_stop() running on the CPU that was previously running our victim task @p. If we find that our task is no longer on that runqueue (this can happen because of a concurrent migration due to load-balance etc.), then we'll end up at the: } else if (dest_cpu < 1 || pending) { branch. Which we'll take because we set pending earlier. Here we first check if the task @p has already satisfied the affinity constraints, if so we bail early [A]. Otherwise we'll reissue migration_cpu_stop() onto the CPU that is now hosting our task @p: stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, &pending->arg, &pending->stop_work); Except, we've never initialized pending->arg, which will be all 0s. This then results in running migration_cpu_stop() on the next CPU with arg->p == NULL, which gives the by now obvious result of fireworks. The cure is to change affine_move_task() to always use pending->arg, furthermore we can use the exact same pattern as the SCA_MIGRATE_ENABLE case, since we'll block on the pending->done completion anyway, no point in adding yet another completion in stop_one_cpu(). This then gives a clear distinction between the two migration_cpu_stop() use cases: - sched_exec() / migrate_task_to() : arg->pending == NULL - affine_move_task() : arg->pending != NULL; And we can have it ignore p->migration_pending when !arg->pending. Any stop work from sched_exec() / migrate_task_to() is in addition to stop works from affine_move_task(), which will be sufficient to issue the completion. Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()") Cc: stable@kernel.org Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Link: https://lkml.kernel.org/r/20210224131355.357743989@infradead.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 8a6edb5257e2a84720fe78cb179eca58ba76126f upstream.

When affine_move_task(p) is called on a running task @p, which is not
otherwise already changing affinity, we'll first set
p->migration_pending and then do:

	 stop_one_cpu(cpu_of_rq(rq), migration_cpu_stop, &arg);

This then gets us to migration_cpu_stop() running on the CPU that was
previously running our victim task @p.

If we find that our task is no longer on that runqueue (this can
happen because of a concurrent migration due to load-balance etc.),
then we'll end up at the:

	} else if (dest_cpu < 1 || pending) {

branch. Which we'll take because we set pending earlier. Here we first
check if the task @p has already satisfied the affinity constraints,
if so we bail early [A]. Otherwise we'll reissue migration_cpu_stop()
onto the CPU that is now hosting our task @p:

	stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
			    &pending->arg, &pending->stop_work);

Except, we've never initialized pending->arg, which will be all 0s.

This then results in running migration_cpu_stop() on the next CPU with
arg->p == NULL, which gives the by now obvious result of fireworks.

The cure is to change affine_move_task() to always use pending->arg,
furthermore we can use the exact same pattern as the
SCA_MIGRATE_ENABLE case, since we'll block on the pending->done
completion anyway, no point in adding yet another completion in
stop_one_cpu().

This then gives a clear distinction between the two
migration_cpu_stop() use cases:

  - sched_exec() / migrate_task_to() : arg->pending == NULL
  - affine_move_task() : arg->pending != NULL;

And we can have it ignore p->migration_pending when !arg->pending. Any
stop work from sched_exec() / migrate_task_to() is in addition to stop
works from affine_move_task(), which will be sufficient to issue the
completion.

Fixes: 6d337eab041d ("sched: Fix migrate_disable() vs set_cpus_allowed_ptr()")
Cc: stable@kernel.org
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210224131355.357743989@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched/features: Fix hrtick reprogramming 2021-03-07T11:35:55+00:00 Juri Lelli juri.lelli@redhat.com 2021-02-08T07:35:53+00:00 f856d6c748da5a6983af0e9e7d6298da581f71e0 [ Upstream commit 156ec6f42b8d300dbbf382738ff35c8bad8f4c3a ] Hung tasks and RCU stall cases were reported on systems which were not 100% busy. Investigation of such unexpected cases (no sign of potential starvation caused by tasks hogging the system) pointed out that the periodic sched tick timer wasn't serviced anymore after a certain point and that caused all machinery that depends on it (timers, RCU, etc.) to stop working as well. This issues was however only reproducible if HRTICK was enabled. Looking at core dumps it was found that the rbtree of the hrtimer base used also for the hrtick was corrupted (i.e. next as seen from the base root and actual leftmost obtained by traversing the tree are different). Same base is also used for periodic tick hrtimer, which might get "lost" if the rbtree gets corrupted. Much alike what described in commit 1f71addd34f4c ("tick/sched: Do not mess with an enqueued hrtimer") there is a race window between hrtimer_set_expires() in hrtick_start and hrtimer_start_expires() in __hrtick_restart() in which the former might be operating on an already queued hrtick hrtimer, which might lead to corruption of the base. Use hrtick_start() (which removes the timer before enqueuing it back) to ensure hrtick hrtimer reprogramming is entirely guarded by the base lock, so that no race conditions can occur. Signed-off-by: Juri Lelli <juri.lelli@redhat.com> Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20210208073554.14629-2-juri.lelli@redhat.com Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 156ec6f42b8d300dbbf382738ff35c8bad8f4c3a ]

Hung tasks and RCU stall cases were reported on systems which were not
100% busy. Investigation of such unexpected cases (no sign of potential
starvation caused by tasks hogging the system) pointed out that the
periodic sched tick timer wasn't serviced anymore after a certain point
and that caused all machinery that depends on it (timers, RCU, etc.) to
stop working as well. This issues was however only reproducible if
HRTICK was enabled.

Looking at core dumps it was found that the rbtree of the hrtimer base
used also for the hrtick was corrupted (i.e. next as seen from the base
root and actual leftmost obtained by traversing the tree are different).
Same base is also used for periodic tick hrtimer, which might get "lost"
if the rbtree gets corrupted.

Much alike what described in commit 1f71addd34f4c ("tick/sched: Do not
mess with an enqueued hrtimer") there is a race window between
hrtimer_set_expires() in hrtick_start and hrtimer_start_expires() in
__hrtick_restart() in which the former might be operating on an already
queued hrtick hrtimer, which might lead to corruption of the base.

Use hrtick_start() (which removes the timer before enqueuing it back) to
ensure hrtick hrtimer reprogramming is entirely guarded by the base
lock, so that no race conditions can occur.

Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20210208073554.14629-2-juri.lelli@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled 2021-03-07T11:35:44+00:00 Peter Zijlstra peterz@infradead.org 2020-08-29T17:22:24+00:00 84c88cbe8822312b8e1e5034d8b543153d6aad7c commit 1b7af295541d75535374325fd617944534853919 upstream. The try_invoke_on_locked_down_task() function currently requires that interrupts be enabled, but it is called with interrupts disabled from rcu_print_task_stall(), resulting in an "IRQs not enabled as expected" diagnostic. This commit therefore updates try_invoke_on_locked_down_task() to use raw_spin_lock_irqsave() instead of raw_spin_lock_irq(), thus allowing use from either context. Link: https://lore.kernel.org/lkml/000000000000903d5805ab908fc4@google.com/ Link: https://lore.kernel.org/lkml/20200928075729.GC2611@hirez.programming.kicks-ass.net/ Reported-by: syzbot+cb3b69ae80afd6535b0e@syzkaller.appspotmail.com Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 1b7af295541d75535374325fd617944534853919 upstream.

The try_invoke_on_locked_down_task() function currently requires
that interrupts be enabled, but it is called with interrupts
disabled from rcu_print_task_stall(), resulting in an "IRQs not
enabled as expected" diagnostic.  This commit therefore updates
try_invoke_on_locked_down_task() to use raw_spin_lock_irqsave() instead
of raw_spin_lock_irq(), thus allowing use from either context.

Link: https://lore.kernel.org/lkml/000000000000903d5805ab908fc4@google.com/
Link: https://lore.kernel.org/lkml/20200928075729.GC2611@hirez.programming.kicks-ass.net/
Reported-by: syzbot+cb3b69ae80afd6535b0e@syzkaller.appspotmail.com
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>