Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934279AbXHYLH7 (ORCPT ); Sat, 25 Aug 2007 07:07:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933207AbXHYLHt (ORCPT ); Sat, 25 Aug 2007 07:07:49 -0400 Received: from mx1.redhat.com ([66.187.233.31]:45251 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764295AbXHYLHr (ORCPT ); Sat, 25 Aug 2007 07:07:47 -0400 To: Steven Rostedt Cc: Ingo Molnar , LKML , RT , Thomas Gleixner , john stultz Subject: Re: [PATCH RT 3/3 - take two ] fix get_monotonic_cycles for latency tracer References: <1187978236.2941.19.camel@localhost.localdomain> <1187982149.4574.1.camel@localhost.localdomain> From: fche@redhat.com (Frank Ch. Eigler) Date: Sat, 25 Aug 2007 07:06:54 -0400 In-Reply-To: <1187982149.4574.1.camel@localhost.localdomain> (Steven Rostedt's message of "Fri, 24 Aug 2007 15:02:29 -0400") Message-ID: User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.3 (gnu/linux) 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: 844 Lines: 23 Steven Rostedt writes: > [...] > + * [...] We don't need to grab > + * any locks, we just keep trying until get all the > + * calculations together in one state. > + * > + * In fact, we __cant__ grab any locks. This > + * function is called from the latency_tracer which can > + * be called anywhere. To grab any locks (including > + * seq_locks) we risk putting ourselves into a deadlock. Perhaps you could add a comment about why the loop, which appears potentially infinite as written, avoids livelock. (It looks rather like a seqlock read loop.) - FChE - 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/