From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 17 Nov 2020 11:14:51 +0000 (+0100)
Subject: sched: Fix migration_cpu_stop() WARN
X-Git-Tag: Ubuntu-5.13.0-19.19~4402^2~23
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=1293771e4353c148d5f6908fb32d1c1cfd653e47;p=mirror_ubuntu-jammy-kernel.git

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>
---

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4d1fd4b783ee..28d541a3c74d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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;
 		}