Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754057AbXJ0PNR (ORCPT ); Sat, 27 Oct 2007 11:13:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751313AbXJ0PNF (ORCPT ); Sat, 27 Oct 2007 11:13:05 -0400 Received: from twin.jikos.cz ([213.151.79.26]:53054 "EHLO twin.jikos.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751182AbXJ0PNE (ORCPT ); Sat, 27 Oct 2007 11:13:04 -0400 Date: Sat, 27 Oct 2007 17:12:41 +0200 (CEST) From: Jiri Kosina To: Gabriel C cc: a.zummo@towertech.it, Linux Kernel Mailing List , Andrew Morton , rtc-linux@googlegroups.com, Peter Zijlstra Subject: Re: BUG: lock held when returning to user space In-Reply-To: <472348F6.6050100@googlemail.com> Message-ID: References: <472348F6.6050100@googlemail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1304 Lines: 30 On Sat, 27 Oct 2007, Gabriel C wrote: > I found that today in dmesg after booting current git ( > ec3b67c11df42362ccda81261d62829042f223f0 ) : > ... > [ 592.752777] > [ 592.752781] ================================================ > [ 592.753478] [ BUG: lock held when returning to user space! ] > [ 592.753880] ------------------------------------------------ > [ 592.754262] hwclock/1452 is leaving the kernel with locks still held! > [ 592.754655] 1 lock held by hwclock/1452: > [ 592.755007] #0: (&rtc->char_lock){--..}, at: [] rtc_dev_open+0x2e/0x7e Yes, this is because rtc keeps a char_lock mutex locked as long as the device is open, to avoid concurrent accessess. It could be easily substituted by some counting -- setting and clearing bit in struct rtc_device instead of using char_lock, but doing this just to shut the lockdep off is questionable imho. Peter, what is the preferred way to annotate these kinds of locking for lockdep to express that it is intended? -- Jiri Kosina - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/