lockdep and oops_in_progress
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From: Dave Airlie on 5 Aug 2010 02:30 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? Dave. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Peter Zijlstra on 5 Aug 2010 04:20 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. Ingo, do you remember anything about that?, I think that bit comes from before my time. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Yong Zhang on 5 Aug 2010 11:10
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. commit e0fdace10e75dac67d906213b780ff1b1a4cc360 Author: David Miller <davem(a)davemloft.net> 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(a)davemloft.net> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> Seems we can revert that commit now because of 'robustify printk'. Dave, what do you think about it? Thanks, Yong > > Ingo, do you remember anything about that?, I think that bit comes from > before my time. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |