Re: 29-rc-mmotm - HID/USB wedge w/ WARNING: at
kernel/workqueue.c:371
[Posted March 18, 2009 by corbet]
| From: |
| Andrew Morton <akpm-AT-linux-foundation.org> |
| To: |
| Lai Jiangshan <laijs-AT-cn.fujitsu.com> |
| Subject: |
| Re: 29-rc-mmotm - HID/USB wedge w/ WARNING: at
kernel/workqueue.c:371 |
| Date: |
| Tue, 17 Mar 2009 19:50:04 -0700 |
| Message-ID: |
| <20090317195004.18fb6af6.akpm@linux-foundation.org> |
| Cc: |
| Valdis.Kletnieks-AT-vt.edu, jkosina-AT-suse.cz, gregkh-AT-suse.de,
linux-kernel-AT-vger.kernel.org, Oleg Nesterov <oleg-AT-tv-sign.ru>,
Oliver Neukum <oliver-AT-neukum.org> |
| Archive‑link: | |
Article |
On Wed, 18 Mar 2009 10:29:40 +0800 Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
> Valdis.Kletnieks@vt.edu wrote:
> > On Tue, 17 Mar 2009 13:54:24 PDT, Andrew Morton said:
> >
> >> It's an error in workqueue-avoid-recursion-in-run_workqueue.patch, methinks.
> >
> > Thanks for the diagnosis - I got as far as realizing that any backtrace that
> > included flush_cpu_workqueue() and worker_thread() had a problem and got
> > stuck there.
> >
>
> It's dangerous when we allow recursion in run_workqueue().
static void run_workqueue(struct cpu_workqueue_struct *cwq)
{
spin_lock_irq(&cwq->lock);
cwq->run_depth++;
if (cwq->run_depth > 3) {
/* morton gets to eat his hat */
printk("%s: recursion depth exceeded: %d\n",
__func__, cwq->run_depth);
dump_stack();
}
That was added five or six years ago, and I never ever got to eat my hat.
> If it's hard for you avoid flush_scheduled_work() in
> keventd's work fuction by other fix, you can create
> another workqueue to handle your works, IMO.
Why do we need to change anything here? No known bugs were fixed, and some
new ones were added.
