linux-kernel - Re: GPF in run_workqueue()/list_del_init(cwq->worklist.next) on resume (was: Re: Help needed: Resume problems in 2.6.32-rc, perhaps related to preempt

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Date:	Wed, 11 Nov 2009 21:20:28 +0100
From:	Marcel Holtmann <marcel@...tmann.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Tejun Heo <tj@...nel.org>, linux-bluetooth@...r.kernel.org
Subject: Re: GPF in run_workqueue()/list_del_init(cwq->worklist.next) on
 resume (was: Re: Help needed: Resume problems in 2.6.32-rc, perhaps related
 to preempt_count leakage in keventd)

Hi Linus,

> > I applied the patch and this is the result of 'dmesg | grep ERR' after 10-or-so
> > consecutive suspend-resume and hibernate-resume cycles:
> > 
> > [  129.008689] ERR!! btusb_waker+0x0/0x27 [btusb]
> > [  166.477373] ERR!! btusb_waker+0x0/0x27 [btusb]
> > [  203.983665] ERR!! btusb_waker+0x0/0x27 [btusb]
> > [  241.636547] ERR!! btusb_waker+0x0/0x27 [btusb]
> > 
> > which kind of confirms my previous observation that the problem was not
> > reproducible without Bluetooth.
> 
> .. and that btusb thing matches my observation that only a few BT drivers 
> seem to use workqueues, and btusb_disconnect() isn't doing any work 
> cancel.
> 
> > I'm going to test the appended patch, then.
> 
> Hmm. the USB disconnect doesn't call hci_dev_put(), it calls 
> hci_free_dev() and doesn't seem to call the ->destruct thing. 
> 
> Although again, maybe that gets called indirectly.
> 
> So I'd put the cancel work in the actual disconnect routine. But maybe 
> thar's just me.

see my other email, I think we have to cancel the waker in btusb_close()
to fix this. However the suspend/resume and auto-suspend has been done
mostly by Oliver and I like to see what he thinks about this.

Regards

Marcel


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