Re: [dm-devel] Soft lockup during suspend since ~2.6.36 [bisected]

[Tejun Heo <tj kernel org>]

Hello,

On Thu, Apr 28, 2011 at 01:51:34AM +0200, Thilo-Alexander Ginkel wrote:
> Well, I get your point. ;-) Maybe this fact can help as a motivator: I
> ran some further tests and while -rc3 seems to be ok (and survived 100
> suspend/resume cycles), the issue strangely seems to be back with -rc4
> (the softlockup call stack that I can see is identical to the photos
> below; the lockup happened after only two cycles).
> 
> > Before I go ahead and try that, do you happen to have softlockup dump?
> > ie. stack traces of the stuck tasks?  I can't find the original
> > posting.
> 
> Sure:
> 
> From <BANLkTi=n4jLsjOYCd0L3hYb30sgPmdv_WA mail gmail com>:
> > Unfortunately, the output via a serial console becomes garbled after
> > "Entering mem sleep", so I went for patching dumpstack_64.c and a
> > couple of other source files to reduce the verbosity. I hope not to
> > have stripped any essential information. The result is available in
> > these pictures:
> >   https://secure.tgbyte.de/dropbox/IeZalo4t-1.jpg
> >   https://secure.tgbyte.de/dropbox/IeZalo4t-2.jpg
> >
> > For both traces, the printed error message reads: "BUG: soft lockup -
> > CPU#3 stuck for 67s! [kblockd:28]"

Does your kernel have preemption enabled?  If not, does the following
patch fix the problem?

Thanks.

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 04ef830..08c7334 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1293,6 +1293,7 @@ __acquires(&gcwq->lock)
 
 		/* CPU has come up inbetween, retry migration */
 		cpu_relax();
+		cond_resched();
 	}
 }