sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable()

migrate_disable(); set_cpus_allowed_ptr(current, {something excluding task_cpu(current)}); affine_move_task(); <-- never returns Signed-off-by: Valentin Schneider <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected]
majek · Nov 10, 2020 · 885b3ba · 885b3ba
1 parent 86fbcd3
commit 885b3ba
Showing 1 changed file with 11 additions and 2 deletions.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
@@ -2238,8 +2238,17 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 		goto out;
 	}
 
-	if (!(flags & SCA_MIGRATE_ENABLE) && cpumask_equal(&p->cpus_mask, new_mask))
-		goto out;
+	if (!(flags & SCA_MIGRATE_ENABLE)) {
+		if (cpumask_equal(&p->cpus_mask, new_mask))
+			goto out;
+
+		if (WARN_ON_ONCE(p == current &&
+				 is_migration_disabled(p) &&
+				 !cpumask_test_cpu(task_cpu(p), new_mask))) {
+			ret = -EBUSY;
+			goto out;
+		}
+	}
 
 	/*
 	 * Picking a ~random cpu helps in cases where we are changing affinity