diff options
| author | Mike Galbraith <efault@gmx.de> | 2010-08-26 05:29:16 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-09-20 13:17:45 -0700 |
| commit | 8c5217d732d576bcdacf7cd515165f246e6a4912 (patch) | |
| tree | 766d33890ae073a66e7ebf3e26d12aa81c1e027f /kernel/sched.c | |
| parent | 6f6198a78a34e3d8623f717d05087267e8dedef2 (diff) | |
sched: revert stable c6fc81a sched: Fix a race between ttwu() and migrate_task()
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 <efault@gmx.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel/sched.c')
| -rw-r--r-- | kernel/sched.c | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index ba2d610f452..48f8dc07648 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2123,10 +2123,12 @@ migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req) /* * 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_struct *p, int src_cpu, int dest_cpu) /* 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; |