linux-kernel - Re: lockdep report at resume

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Date:	Tue, 21 Apr 2009 16:11:03 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Oliver Neukum <oliver@...kum.org>,
	Johannes Berg <johannes@...solutions.net>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input <linux-input@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: lockdep report at resume

On Tue, 21 Apr 2009, Oliver Neukum wrote:

> > [ thanks for the analysis Johannes ... involving also Oliver here; really
> >   seems like a false positive to me ]
> I think he's right. But as a matter of principle I'd like to see 
> flush_scheduled_work() avoided where possible, hence the patch.

I am not entirely sure that this is the same issue as the one from #13136 
of kernel.org bugzilla.

Anyway, for reference, the patch Oliver mentioned here is below.

>From oliver@...kum.org Tue Apr 21 15:38:41 2009
Date: Tue, 21 Apr 2009 15:38:12 +0200
From: Oliver Neukum <oliver@...kum.org>
To: Andrew Morton <akpm@...ux-foundation.org>, casteyde.christian@...e.fr
Cc: Jiri Kosina <jkosina@...e.cz>, Rafael J. Wysocki <rjw@...k.pl>
Subject: Re: [Bugme-new] [Bug 13136] New: possible circular locking dependency detected while suspending laptop to S3

Am Dienstag 21 April 2009 01:01:13 schrieb Andrew Morton:
> On Sat, 18 Apr 2009 11:17:47 GMT
>
> bugzilla-daemon@...zilla.kernel.org wrote:
> > http://bugzilla.kernel.org/show_bug.cgi?id=13136
>
> Looks like a post-2.6.29 regression in usb-hid.  usbhid_close() holding
> hid_open_mut while doing flush_scheduled_work().
>
> Could you gents please work out where the problem is and suitably
> assign the report?

Please test this patch.

	Regards
		Oliver

---

commit 4bdc818cca662000cf195b1e83e8a0f8a3f0b9c6
Author: Oliver Neukum <oneukum@...ux-d698.(none)>
Date:   Tue Apr 21 15:33:41 2009 +0200

    avoid deadlock in usbhid_close by cancelling workqueues

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 4306cb1..900ce18 100644
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -662,8 +662,8 @@ void usbhid_close(struct hid_device *hid)
 	spin_lock_irq(&usbhid->lock);
 	if (!--hid->open) {
 		spin_unlock_irq(&usbhid->lock);
+		hid_cancel_delayed_stuff(usbhid);
 		usb_kill_urb(usbhid->urbin);
-		flush_scheduled_work();
 		usbhid->intf->needs_remote_wakeup = 0;
 	} else {
 		spin_unlock_irq(&usbhid->lock);

Thanks,

-- 
Jiri Kosina
SUSE Labs
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