From: Mike Galbraith This commit does not appear to have been meant for 32-stable, and causes ltp's cpusets testcases to fail, revert it. Original commit text: sched: Fix a race between ttwu() and migrate_task() Based on commit e2912009fb7b715728311b0d8fe327a1432b3f79 upstream, but done differently as this issue is not present in .33 or .34 kernels due to rework in this area. If a task is in the TASK_WAITING state, then try_to_wake_up() is working on it, and it will place it on the correct cpu. This commit ensures that neither migrate_task() nor __migrate_task() calls set_task_cpu(p) while p is in the TASK_WAKING state. Otherwise, there could be two concurrent calls to set_task_cpu(p), resulting in the task's cfs_rq being inconsistent with its cpu. Signed-off-by: Mike Galbraith Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Greg Kroah-Hartman --- kernel/sched.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2123,10 +2123,12 @@ migrate_task(struct task_struct *p, int /* * If the task is not on a runqueue (and not running), then - * the next wake-up will properly place the task. + * it is sufficient to simply update the task's cpu field. */ - if (!p->se.on_rq && !task_running(rq, p)) + if (!p->se.on_rq && !task_running(rq, p)) { + set_task_cpu(p, dest_cpu); return 0; + } init_completion(&req->done); req->task = p; @@ -7217,9 +7219,6 @@ static int __migrate_task(struct task_st /* Already moved. */ if (task_cpu(p) != src_cpu) goto done; - /* Waking up, don't get in the way of try_to_wake_up(). */ - if (p->state == TASK_WAKING) - goto fail; /* Affinity changed (again). */ if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) goto fail; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/