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From e9faaf024fdd553b55aaed31855385da7e9d505a Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 8 Jun 2021 00:37:34 -0400
Subject: [PATCH 293/323] sched: Fix affine_move_task() self-concurrency
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
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: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/sched/core.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e28fb33afa95..76fa3daf1f60 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1916,6 +1916,7 @@ struct migration_arg {
struct set_affinity_pending {
refcount_t refs;
+ unsigned int stop_pending;
struct completion done;
struct cpu_stop_work stop_work;
struct migration_arg arg;
@@ -2034,12 +2035,15 @@ static int migration_cpu_stop(void *data)
* determine is_migration_disabled() and so have to chase after
* it.
*/
+ WARN_ON_ONCE(!pending->stop_pending);
task_rq_unlock(rq, p, &rf);
stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
&pending->arg, &pending->stop_work);
return 0;
}
out:
+ if (pending)
+ pending->stop_pending = false;
task_rq_unlock(rq, p, &rf);
if (complete)
@@ -2235,7 +2239,7 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
int dest_cpu, unsigned int flags)
{
struct set_affinity_pending my_pending = { }, *pending = NULL;
- bool complete = false;
+ bool stop_pending, complete = false;
/* Can the task run on the task's current CPU? If so, we're done */
if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
@@ -2308,14 +2312,19 @@ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flag
* anything else we cannot do is_migration_disabled(), punt
* and have the stopper function handle it all race-free.
*/
+ stop_pending = pending->stop_pending;
+ if (!stop_pending)
+ pending->stop_pending = true;
refcount_inc(&pending->refs); /* pending->{arg,stop_work} */
if (flags & SCA_MIGRATE_ENABLE)
p->migration_flags &= ~MDF_PUSH;
task_rq_unlock(rq, p, rf);
- stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
- &pending->arg, &pending->stop_work);
+ if (!stop_pending) {
+ stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
+ &pending->arg, &pending->stop_work);
+ }
if (flags & SCA_MIGRATE_ENABLE)
return 0;
--
2.43.0
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