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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2012-05-17 19:19:46 (GMT) |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2012-06-06 14:52:26 (GMT) |
| commit | 7f1b43936f0ecad14770634c021cf4a929aec74d (patch) | |
| tree | ea200fcf70af41839e049c59a2dc922407e7495b /kernel/sched | |
| parent | 10717dcde10d09f9fcee53a12a4236af1a82b484 (diff) | |
| download | linux-7f1b43936f0ecad14770634c021cf4a929aec74d.tar.xz | |
sched/rt: Fix lockdep annotation within find_lock_lowest_rq()
Roland Dreier reported spurious, hard to trigger lockdep warnings
within the scheduler - without any real lockup.
This bit gives us the right clue:
> [89945.640512] [<ffffffff8103fa1a>] double_lock_balance+0x5a/0x90
> [89945.640568] [<ffffffff8104c546>] push_rt_task+0xc6/0x290
if you look at that code you'll find the double_lock_balance() in
question is the one in find_lock_lowest_rq() [yay for inlining].
Now find_lock_lowest_rq() has a bug.. it fails to use
double_unlock_balance() in one exit path, if this results in a retry in
push_rt_task() we'll call double_lock_balance() again, at which point
we'll run into said lockdep confusion.
Reported-by: Roland Dreier <roland@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1337282386.4281.77.camel@twins
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/rt.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 2a4e8df..573e1ca 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1562,7 +1562,7 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq) task_running(rq, task) || !task->on_rq)) { - raw_spin_unlock(&lowest_rq->lock); + double_unlock_balance(rq, lowest_rq); lowest_rq = NULL; break; } |