From da8d5089da6dfd54e5fd05d0c291a63c2bcf6885 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 7 Jan 2009 15:28:57 +0100 Subject: 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: [] task_rq_lock+0x45/0x7e > > but task is already holding lock: > (&rq->lock){++..}, at: [] 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 Signed-off-by: Ingo Molnar --- kernel/sched.c | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'kernel') 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; -- cgit v1.2.3