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SubjectRe: [BUG] 2.6.28-git LOCKDEP: Possible recursive rq->lock
* Peter Zijlstra <a.p.zijlstra@chello.nl> [2009-01-07 14:12:43]:

> On Wed, 2009-01-07 at 17:59 +0530, Vaidyanathan Srinivasan wrote:
>
> > =============================================
> > [ 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
> >
> > other info that might help us debug this:
> > 1 lock held by klogd/5062:
> > #0: (&rq->lock){++..}, at: [<ffffffff805f7354>] schedule+0x158/0xa31
> >
> > stack backtrace:
> > Pid: 5062, comm: klogd Not tainted 2.6.28-autotest-tip-sv #1
> > Call Trace:
> > [<ffffffff80259ef1>] __lock_acquire+0xeb9/0x16a4
> > [<ffffffff8025a6c0>] ? __lock_acquire+0x1688/0x16a4
> > [<ffffffff8025a761>] lock_acquire+0x85/0xa9
> > [<ffffffff8022aca2>] ? task_rq_lock+0x45/0x7e
> > [<ffffffff805fa4d4>] _spin_lock+0x31/0x66
> > [<ffffffff8022aca2>] ? task_rq_lock+0x45/0x7e
> > [<ffffffff8022aca2>] task_rq_lock+0x45/0x7e
> > [<ffffffff80233363>] try_to_wake_up+0x88/0x27a
> > [<ffffffff80233581>] wake_up_process+0x10/0x12
> > [<ffffffff805f775c>] schedule+0x560/0xa31
>
> I'd be most curious to know where in schedule we are.

ok, we are in sched.c:3777

double_unlock_balance(this_rq, busiest);
if (active_balance)
>>>>>>>>>>> wake_up_process(busiest->migration_thread);

} else

In active balance in newidle. This implies sched_mc was 2 at that time.
let me trace this and debug further.

--Vaidy



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