Re: lockdep and oops_in_progress
From: Yong Zhang
Date: Thu Aug 05 2010 - 11:05:20 EST
On Thu, Aug 05, 2010 at 10:10:49AM +0200, Peter Zijlstra wrote:
> On Thu, 2010-08-05 at 16:21 +1000, Dave Airlie wrote:
> > Hi guys,
> > I was debugging a wierd issue with suspend/resume and fbcon/X with
> > some recent work Jesse and myself did to try and make sure a pinned
> > fbcon always gets the text on it with a panic or oops occurs.
> > It does this by testing the oops_in_progress flag, however once any
> > lockdep issue occurs it looks to me that we leave this flag set
> > forever, in most places I can see in oops code etc they call
> > bust_spinlocks(1) then bust_spinlocks(0) to balance the
> > oops_in_progress value, but lockdep never seems to reset it.
> > I'm wondering if there is an inherent reason for this or if I whip up
> > a patch to reset once the lockdep is printed if this would cause any
> > issues?
> That's debug_locks_off(), right? I don't think there's a particular
> reason we keep it set, cleaning that up might take a bit of work but
> shouldn't be too hard.
Author: David Miller <davem@xxxxxxxxxxxxx>
Date: Fri Aug 1 01:11:22 2008 -0700
debug_locks: set oops_in_progress if we will log messages.
Otherwise lock debugging messages on runqueue locks can deadlock the
system due to the wakeups performed by printk().
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Seems we can revert that commit now because of 'robustify printk'.
Dave, what do you think about it?
> Ingo, do you remember anything about that?, I think that bit comes from
> before my time.
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