linux-kernel - Re: [linux-pm] Help needed: Resume problems in 2.6.32-rc, perhaps related to preempt

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Date:	Mon, 9 Nov 2009 16:24:55 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Greg KH <gregkh@...e.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [linux-pm] Help needed: Resume problems in 2.6.32-rc, perhaps
 related to preempt_count leakage in keventd

On Mon, 9 Nov 2009, Rafael J. Wysocki wrote:

> On Monday 09 November 2009, Alan Stern wrote:
> > On Mon, 9 Nov 2009, Rafael J. Wysocki wrote:
> > 
> > > Still, RIP always points to list_del_init(cwq->worklist.next); in
> > > run_workqueue().
> > 
> > Use a big hammer: Create a new global variable, set it to 1 while
> > resuming and back to 0 after the tasks have been thawed.  While the
> > variable is nonzero, print in the log the list pointers in
> > cwq->worklist just before executing the list_del_init().  Maybe also 
> > print some other interesting information about cwq.
> 
> I've just sent a message containing full call trace.
> 
> It shows the problem is a general protection fault that happens _after_ we've
> thawed tasks.

Okay, so set the variable to 1 when the tasks are thawed and back to 0 
a second later.  The point is that you _can_ get more detailed 
information about the bad data values without flooding the system log.

Alan Stern

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