linux-kernel - Re: linux-next: Tree for April 14 (Call-traces: RCU/ACPI/WQ related?)

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Message-ID: <20110422005046.GQ2235@linux.vnet.ibm.com>
Date:	Thu, 21 Apr 2011 17:50:46 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	sedat.dilek@...il.com
Cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: linux-next: Tree for April 14 (Call-traces: RCU/ACPI/WQ
 related?)

On Thu, Apr 21, 2011 at 04:47:31PM +0200, Sedat Dilek wrote:
> On Thu, Apr 21, 2011 at 4:28 PM, Paul E. McKenney
> <paulmck@...ux.vnet.ibm.com> wrote:
> > On Thu, Apr 21, 2011 at 02:49:37PM +0200, Sedat Dilek wrote:
> >> On Thu, Apr 21, 2011 at 12:24 PM, Sedat Dilek
> >> <sedat.dilek@...glemail.com> wrote:

[ . . . ]

> >> Here the results from the 2nd-run (PREEMPT_RCU enabled).
> >
> > OK, and the grace periods clearly stopped advancing early on.
> >
> > Beyond that point, the per-CPU kthread is blocked, but RCU has some
> > work for it to do.  So someone has called invoke_rcu_cpu_kthread(),
> > but rcu_cpu_kthread() is still blocked.  I don't see a bug right
> > off-hand, but it is early in the morning for me, so I might easily
> > be missing something.
> >
> > Hmmm...
> >
> > The synchronization between these two assumes that the per-CPU
> > kthread is always bound to the respective CPU, so if was somehow
> > being migrated off, that might explain these results.
> >
> > I will add some more diagnostics, test them locally, then push
> > out an update.  Seem reasonable?
> >
> > And thank you again for the testing!!!
> 
> Ping me when you have new stuff for testing.
> Tomorrow (friday), here is public holiday and monday, too.
> So a looong weekend.

;-)

OK, I have a new sedat.2011.04.21a branch in the -rcu git tree:

git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git

This is against 2.6.39-rc3, as before.  (Yes, I do need to rebase to
2.6.39-rc4, but didn't want to change any more than I had to.)

I also have an updated script, which is attached.  The output is similar
to the earlier one, and it operated is pretty much the same way.

Have a great weekend, and I look forward to seeing what shows up on
this round.  I confess to still being quite puzzled!

							Thanx, Paul

Download attachment "collectdebugfs.sh" of type "application/x-sh" (1633 bytes)