linux-kernel - Re: [PATCH 6/6] workqueue: reimplement WQ_HIGHPRI using a separate worker

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Date:	Fri, 13 Jul 2012 10:08:00 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	joshhunt00@...il.com, axboe@...nel.dk, rni@...gle.com,
	vgoyal@...hat.com, vwadekar@...dia.com,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-crypto@...r.kernel.org, swhiteho@...hat.com, bpm@....com,
	elder@...nel.org, xfs@....sgi.com, marcel@...tmann.org,
	gustavo@...ovan.org, johan.hedberg@...il.com,
	linux-bluetooth@...r.kernel.org, martin.petersen@...cle.com,
	Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH 6/6] workqueue: reimplement WQ_HIGHPRI using a separate
 worker_pool

On Thu, Jul 12, 2012 at 02:45:14PM -0700, Tejun Heo wrote:
> Hello, again.
> 
> On Thu, Jul 12, 2012 at 10:05:19AM -0700, Tejun Heo wrote:
> > On Thu, Jul 12, 2012 at 09:06:48PM +0800, Fengguang Wu wrote:
> > > [    0.207977] WARNING: at /c/kernel-tests/mm/kernel/workqueue.c:1217 worker_enter_idle+0x2b8/0x32b()
> > > [    0.207977] Modules linked in:
> > > [    0.207977] Pid: 1, comm: swapper/0 Not tainted 3.5.0-rc6-08414-g9645fff #15
> > > [    0.207977] Call Trace:
> > > [    0.207977]  [<ffffffff81087189>] ? worker_enter_idle+0x2b8/0x32b
> > > [    0.207977]  [<ffffffff810559d9>] warn_slowpath_common+0xae/0xdb
> > > [    0.207977]  [<ffffffff81055a2e>] warn_slowpath_null+0x28/0x31
> > > [    0.207977]  [<ffffffff81087189>] worker_enter_idle+0x2b8/0x32b
> > > [    0.207977]  [<ffffffff81087222>] start_worker+0x26/0x42
> > > [    0.207977]  [<ffffffff81c8b261>] init_workqueues+0x2d2/0x59a
> > > [    0.207977]  [<ffffffff81c8af8f>] ? usermodehelper_init+0x8a/0x8a
> > > [    0.207977]  [<ffffffff81000284>] do_one_initcall+0xce/0x272
> > > [    0.207977]  [<ffffffff81c6f650>] kernel_init+0x12e/0x3c1
> > > [    0.207977]  [<ffffffff814b9b74>] kernel_thread_helper+0x4/0x10
> > > [    0.207977]  [<ffffffff814b80b0>] ? retint_restore_args+0x13/0x13
> > > [    0.207977]  [<ffffffff81c6f522>] ? start_kernel+0x737/0x737
> > > [    0.207977]  [<ffffffff814b9b70>] ? gs_change+0x13/0x13
> > 
> > Yeah, I forgot to flip the WARN_ON_ONCE() condition so that it checks
> > nr_running before looking at pool->nr_running.  The warning is
> > spurious.  Will post fix soon.
> 
> I was wrong and am now dazed and confused.  That's from
> init_workqueues() where only cpu0 is running.  How the hell did
> nr_running manage to become non-zero at that point?  Can you please
> apply the following patch and report the boot log?  Thank you.

Tejun, here is the data I got:

[    0.165669] Performance Events: unsupported Netburst CPU model 6 no PMU driver, software events only.
[    0.167001] XXX cpu=0 gcwq=ffff88000dc0cfc0 base=ffff88000dc11e80
[    0.167989] XXX cpu=0 nr_running=0 @ ffff88000dc11e80
[    0.168988] XXX cpu=0 nr_running=0 @ ffff88000dc11e88
[    0.169988] XXX cpu=1 gcwq=ffff88000dd0cfc0 base=ffff88000dd11e80
[    0.170988] XXX cpu=1 nr_running=0 @ ffff88000dd11e80
[    0.171987] XXX cpu=1 nr_running=0 @ ffff88000dd11e88
[    0.172988] XXX cpu=8 nr_running=0 @ ffffffff81d7c430
[    0.173987] XXX cpu=8 nr_running=12 @ ffffffff81d7c438
[    0.175416] ------------[ cut here ]------------
[    0.175981] WARNING: at /c/wfg/linux/kernel/workqueue.c:1220 worker_enter_idle+0x2b8/0x32b()
[    0.175981] Modules linked in:
[    0.175981] Pid: 1, comm: swapper/0 Not tainted 3.5.0-rc6-bisect-next-20120712-dirty #102
[    0.175981] Call Trace:
[    0.175981]  [<ffffffff81087455>] ? worker_enter_idle+0x2b8/0x32b
[    0.175981]  [<ffffffff810559d1>] warn_slowpath_common+0xae/0xdb
[    0.175981]  [<ffffffff81055a26>] warn_slowpath_null+0x28/0x31
[    0.175981]  [<ffffffff81087455>] worker_enter_idle+0x2b8/0x32b
[    0.175981]  [<ffffffff810874ee>] start_worker+0x26/0x42
[    0.175981]  [<ffffffff81c7dc4d>] init_workqueues+0x370/0x638
[    0.175981]  [<ffffffff81c7d8dd>] ? usermodehelper_init+0x8a/0x8a
[    0.175981]  [<ffffffff81000284>] do_one_initcall+0xce/0x272
[    0.175981]  [<ffffffff81c62652>] kernel_init+0x12e/0x3c1
[    0.175981]  [<ffffffff814b6e74>] kernel_thread_helper+0x4/0x10
[    0.175981]  [<ffffffff814b53b0>] ? retint_restore_args+0x13/0x13
[    0.175981]  [<ffffffff81c62524>] ? start_kernel+0x739/0x739
[    0.175981]  [<ffffffff814b6e70>] ? gs_change+0x13/0x13
[    0.175981] ---[ end trace c22d98677c4d3e37 ]---
[    0.178091] Testing tracer nop: PASSED

The attached dmesg is not complete because, once get the oops message,
my script will kill the kvm to save time.

Thanks,
Fengguang

View attachment "dmesg-kvm_bisect-waimea-27649-2012-07-13-08-34-35" of type "text/plain" (93871 bytes)