Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754188Ab2KUNnB (ORCPT ); Wed, 21 Nov 2012 08:43:01 -0500 Received: from lxorguk.ukuu.org.uk ([81.2.110.251]:34355 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751640Ab2KUNm6 (ORCPT ); Wed, 21 Nov 2012 08:42:58 -0500 Date: Wed, 21 Nov 2012 13:47:47 +0000 From: Alan Cox To: Ivo Sieben Cc: Oleg Nesterov , linux-kernel@vger.kernel.org, Andi Kleen , Peter Zijlstra , Ingo Molnar , linux-serial@vger.kernel.org, Alan Cox , Greg KH Subject: Re: [REPOST-v2] sched: Prevent wakeup to enter critical section needlessly Message-ID: <20121121134747.261c426a@pyramind.ukuu.org.uk> In-Reply-To: References: <1351159974-980-1-git-send-email-meltedpianoman@gmail.com> <1353310211-3011-1-git-send-email-meltedpianoman@gmail.com> <20121119151050.GA4270@redhat.com> <20121119154940.GA6354@redhat.com> X-Mailer: Claws Mail 3.8.1 (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: 589 Lines: 14 > But we try to understand your fault scenario: How can the LOAD leak > into the critical section? As far as we understand the spin_unlock() > function also contains a memory barrier to prevent such a reordering > from happening. It does - it would be very interesting for someone to look at the assembly if this is making a difference. 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/