From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Peter Zijlstra peterz@infradead.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 --- kernel/sched/core.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1864,6 +1864,7 @@ 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; @@ -1982,12 +1983,15 @@ 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) @@ -2183,7 +2187,7 @@ static int affine_move_task(struct rq *r 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)) { @@ -2256,14 +2260,19 @@ static int affine_move_task(struct rq *r * 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;