From: Yong Zhang <yong.zhang0@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Airlie <airlied@gmail.com>, Ingo Molnar <mingo@redhat.com>,
Jesse Barnes <jbarnes@virtuousgeek.org>,
LKML <linux-kernel@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: lockdep and oops_in_progress
Date: Thu, 5 Aug 2010 22:59:40 +0800 [thread overview]
Message-ID: <20100805145940.GA8685@zhy> (raw)
In-Reply-To: <1280995849.1923.1515.camel@laptop>
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@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@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@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.
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next prev parent reply other threads:[~2010-08-05 15:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-05 6:21 lockdep and oops_in_progress Dave Airlie
2010-08-05 8:10 ` Peter Zijlstra
2010-08-05 14:59 ` Yong Zhang [this message]
2010-09-23 3:57 ` Dave Airlie
2010-11-02 20:51 ` Dave Airlie
2010-11-02 20:53 ` David Miller
2010-11-02 20:54 ` David Miller
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