Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161205AbWKFI6T (ORCPT ); Mon, 6 Nov 2006 03:58:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161208AbWKFI6T (ORCPT ); Mon, 6 Nov 2006 03:58:19 -0500 Received: from gate.crashing.org ([63.228.1.57]:61848 "EHLO gate.crashing.org") by vger.kernel.org with ESMTP id S1161205AbWKFI6S (ORCPT ); Mon, 6 Nov 2006 03:58:18 -0500 Subject: Re: PATCH? hrtimer_wakeup: fix a theoretical race wrt rt_mutex_slowlock() From: Benjamin Herrenschmidt To: Linus Torvalds Cc: Oleg Nesterov , Thomas Gleixner , Steven Rostedt , Andrew Morton , linux-kernel@vger.kernel.org In-Reply-To: References: <20061105193457.GA3082@oleg> Content-Type: text/plain Date: Mon, 06 Nov 2006 19:57:51 +1100 Message-Id: <1162803471.28571.303.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.8.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1004 Lines: 24 > Yes. On x86 (and x86-64) you'll never see this, because writes are always > seen in order regardless, and in addition, the spin_lock is actually > totally serializing anyway. On most other architectures, the spin_lock > will serialize all the writes too, but it's not guaranteed, so in theory > you're right. I suspect no actual architecture will do this, but hey, > when talking memory ordering, safe is a lot better than sorry. PowerPC doesn't serialize the writes on spin_lock, only on spin_unlock. (That is, previous writes can "leak" into the lock, but writes done before the unlock can't leak out of the spinlock). Now, I've just glanced at the thread, so I don't know if that's relevant to the problems you guys are talking about :-) Ben. - 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/