linux-kernel - wacom + runtime PM = AA deadlock

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Message-ID: <4C8E180D.4020309@suse.cz>
Date:	Mon, 13 Sep 2010 14:24:45 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	pingc@...om.com
CC:	Dmitry Torokhov <dtor@...l.ru>, linux-input@...r.kernel.org,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	linux-pm <linux-pm@...ts.linux-foundation.org>
Subject: wacom + runtime PM = AA deadlock

Hi,

by mistake when runtime PM is enabled by default for input devices, X
hangs on wacom open:
[<ffffffff814a00ea>] mutex_lock+0x1a/0x40
[<ffffffffa02bc94b>] wacom_resume+0x3b/0x90 [wacom]
[<ffffffff81327a32>] usb_resume_interface+0xd2/0x190
[<ffffffff81327b5d>] usb_resume_both+0x6d/0x110
[<ffffffff81327c24>] usb_runtime_resume+0x24/0x40
[<ffffffff8130a2cf>] __pm_runtime_resume+0x26f/0x450
[<ffffffff8130a23a>] __pm_runtime_resume+0x1da/0x450
[<ffffffff8130a53a>] pm_runtime_resume+0x2a/0x50
[<ffffffff81328176>] usb_autopm_get_interface+0x26/0x60
[<ffffffffa02bc626>] wacom_open+0x36/0x90 [wacom]

wacom_open took wacom->lock and calls usb_autopm_get_interface which in
turn calls wacom_resume which tries to aquire the lock again.

More details (dmesg including) at:
https://bugzilla.novell.com/show_bug.cgi?id=638506

Any ideas how to fix that properly?

thanks,
-- 
js
suse labs
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