Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761894Ab2ERLiH (ORCPT ); Fri, 18 May 2012 07:38:07 -0400 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:50179 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752529Ab2ERLiF (ORCPT ); Fri, 18 May 2012 07:38:05 -0400 Date: Fri, 18 May 2012 12:40:51 +0100 From: Alan Cox To: Rabin Vincent Cc: alan@linux.intel.com, gregkh@linuxfoundation.org, LKML Subject: Re: Race in vt_event_wait() during suspend/resume Message-ID: <20120518124051.6cd03ab0@pyramind.ukuu.org.uk> In-Reply-To: References: X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.8; x86_64-redhat-linux-gnu) Face: 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 Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 955 Lines: 33 On Fri, 18 May 2012 16:34:53 +0530 Rabin Vincent wrote: > pm_restore_console() is called from the suspend/resume path, > this calls vt_move_to_console(), which calls vt_event_wait(). > > There's a race in this path which causes the process > which requests the suspend to sleep indefinitely waiting > for an event which already happened: > > P1 P2 > vt_move_to_console() > set_console() > schedule_console_callback() > vt_waitactive() > check n == fg_console +1 > console_callback() > switch_screen() > vt_event_post() // no waiters > > vt_event_wait() // forever > > I think the following should fix it. Comments? > Looks right to me. Alan -- 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/