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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-01-07 15:28:57 +0100
committerIngo Molnar <mingo@elte.hu>2009-01-07 16:10:54 +0100
commitda8d5089da6dfd54e5fd05d0c291a63c2bcf6885 (patch)
treead9f7deceed846e56e0185976af5c620722ff9ba
parentede6f5aea054d3fb67c78857f7abdee602302043 (diff)
sched: fix possible recursive rq->lock
Vaidyanathan Srinivasan reported: > ============================================= > [ INFO: possible recursive locking detected ] > 2.6.28-autotest-tip-sv #1 > --------------------------------------------- > klogd/5062 is trying to acquire lock: > (&rq->lock){++..}, at: [<ffffffff8022aca2>] task_rq_lock+0x45/0x7e > > but task is already holding lock: > (&rq->lock){++..}, at: [<ffffffff805f7354>] schedule+0x158/0xa31 With sched_mc at 2. (it is default-off) Strictly speaking we'll not deadlock, because ttwu will not be able to place the migration task on our rq, but since the code can deal with both rqs getting unlocked, this seems the easiest way out. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 2e3545f57e7..deb5ac8c12f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3728,8 +3728,13 @@ redo:
}
double_unlock_balance(this_rq, busiest);
+ /*
+ * Should not call ttwu while holding a rq->lock
+ */
+ spin_unlock(&this_rq->lock);
if (active_balance)
wake_up_process(busiest->migration_thread);
+ spin_lock(&this_rq->lock);
} else
sd->nr_balance_failed = 0;