Commit 1293771e authored Nov 17, 2020 by Peter Zijlstra

sched: Fix migration_cpu_stop() WARN



Oleksandr reported hitting the WARN in the 'task_rq(p) != rq' branch
of migration_cpu_stop(). Valentin noted that using cpu_of(rq) in that
case is just plain wrong to begin with, since per the earlier branch
that isn't the actual CPU of the task.

Replace both instances of is_cpu_allowed() by a direct p->cpus_mask
test using task_cpu().

Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Debugged-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

parent d707faa6

kernel/sched/core.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1911,7 +1911,7 @@ static int migration_cpu_stop(void *data)
		* and we should be valid again. Nothing to do.
		*/
		if (!pending) {
		WARN_ON_ONCE(!is_cpu_allowed(p, cpu_of(rq)));
		WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask));
		goto out;
		}

		@@ -1950,7 +1950,7 @@ static int migration_cpu_stop(void *data)
		* valid again. Nothing to do.
		*/
		if (!pending) {
		WARN_ON_ONCE(!is_cpu_allowed(p, cpu_of(rq)));
		WARN_ON_ONCE(!cpumask_test_cpu(task_cpu(p), &p->cpus_mask));
		goto out;
		}