Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161080AbXBTXXZ (ORCPT ); Tue, 20 Feb 2007 18:23:25 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161081AbXBTXXZ (ORCPT ); Tue, 20 Feb 2007 18:23:25 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:48054 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1161080AbXBTXXY (ORCPT ); Tue, 20 Feb 2007 18:23:24 -0500 Date: Mon, 19 Feb 2007 23:47:25 +0100 From: Pavel Machek To: Oleg Nesterov Cc: Andrew Morton , "Rafael J. Wysocki" , "Paul E. McKenney" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] fix refrigerator() vs thaw_process() race Message-ID: <20070219224725.GF21199@elf.ucw.cz> References: <20070218221737.GA4880@tv-sign.ru> <20070219105008.GA19184@elf.ucw.cz> <20070219121236.GD91@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070219121236.GD91@tv-sign.ru> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1475 Lines: 44 Hi! > > > refrigerator() can miss a wakeup, "wait event" loop needs a proper memory > > > ordering. > > > > > > Signed-off-by: Oleg Nesterov > > > > > > --- WQ/kernel/power/process.c~WAKE 2007-02-18 22:56:49.000000000 +0300 > > > +++ WQ/kernel/power/process.c 2007-02-19 01:04:26.000000000 +0300 > > > @@ -46,8 +46,10 @@ void refrigerator(void) > > > recalc_sigpending(); /* We sent fake signal, clean it up */ > > > spin_unlock_irq(¤t->sighand->siglock); > > > > > > - current->state = TASK_UNINTERRUPTIBLE; > > > + set_current_state(TASK_UNINTERRUPTIBLE); > > > > > > Looks okay to me... but this one liner would be exactly as effective, > > right? > > I think no, with this one liner we have > > while (frozen(current)) { > // ------ WINDOW ------------ > set_current_state(TASK_UNINTERRUPTIBLE); > schedule(); > } > > What if thaw_process() happens in the window above? > > We need the barrier exactly because LOAD (check condition) should not > come before STORE (set task->state). Aha, ok :-). You already have my ACK ;-). Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/