linux-kernel - Re: Linux 2.6.22-rc4

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Date:	Tue, 5 Jun 2007 22:19:54 +0200
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pm@...ts.linux-foundation.org,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: Linux 2.6.22-rc4

Hi!

> > > [ 116.733327] PM: suspend-to-disk mode set to 'shutdown' [ 
> > > 116.738849] swsusp: Basic memory bitmaps created [ 116.745353] 
> > > Stopping tasks ... WARNING: at 
> > > /home/devel/linux-git/kernel/lockdep.c:2414 check_flags()
> 
> > > [  116.755052] irq event stamp: 69
> > > [  116.755060] hardirqs last  enabled at (69): [<c04040f9>] syscall_exit_work+0x11/0x26
> > > [  116.755084] hardirqs last disabled at (68): [<c0403fdd>] syscall_exit+0x9/0x1a
> > > [  116.755109] softirqs last  enabled at (0): [<c042150c>] copy_process+0x4dd/0x1286
> > > [  116.755139] softirqs last disabled at (0): [<00000000>] 0x0
> > > [  116.945776] done.
> 
> > Well, it's harmless in the sense that "yeah, the system still works", 
> > but it does seem to be a real bug. We have hardware interrupts 
> > disabled when we _think_ we should have them on, so our irq tracking 
> > is off.
> > 
> > Ingo, do you see what's up? It looks like we got a signal to a process 
> > that just got created, is the setup stuff for "tsk->hardirqs_enabled" 
> > perhaps off a bit?
> 
> hm. I cannot see the source of the bug at the moment, but here's my 
> analysis so far:
> 
> the last event that irqtrace got was #69, and that was a 'hardirqs on' 
> in syscall_exit_work. After that we did a 'hardirqs off' without 
> properly tracking that via irqtrace. Next time we got an irqtrace event 
> (event 70) the assert caught up with us and turned off lockdep and 
> backed out of that function. This was in:
> 
>  > [  116.754957]  [<c043c3e5>] check_flags+0x95/0x143
>  > [  116.754967]  [<c043f158>] lock_acquire+0x29/0x82
>  > [  116.754977]  [<c06313a7>] _spin_lock+0x35/0x42
>  > [  116.754990]  [<c044894a>] refrigerator+0x14/0xc6
>  > [  116.755002]  [<c042d4b3>] get_signal_to_deliver+0x33/0x397
>  > [  116.755016]  [<c0403597>] do_notify_resume+0x94/0x6ed
>  > [  116.755029]  [<c0404099>] work_notifysig+0x13/0x1a
> 
> isnt the refrigerator() suspend related? Perhaps suspend disables irqs 
> somewhere that we forgot to track?

refrigerator is suspend related, but I do not think it does any
interrupt magic. We do magic later in hibernation process.

This is in kernel/power/process.c, we have spinlock_irqsave there, but
that's pretty much it AFAICT.
								Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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