Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764620AbZDCLb1 (ORCPT ); Fri, 3 Apr 2009 07:31:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1762213AbZDCLbS (ORCPT ); Fri, 3 Apr 2009 07:31:18 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:43485 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761120AbZDCLbR (ORCPT ); Fri, 3 Apr 2009 07:31:17 -0400 Date: Fri, 3 Apr 2009 13:30:58 +0200 From: Ingo Molnar To: "Metzger, Markus T" Cc: "tglx@linutronix.de" , "hpa@zytor.com" , "markus.t.metzger@gmail.com" , "roland@redhat.com" , "eranian@googlemail.com" , "oleg@redhat.com" , "Villacis, Juan" , "ak@linux.jf.intel.com" , "linux-kernel@vger.kernel.org" Subject: Re: [patch 01/18] x86, bts: fix race when bts tracer is removed Message-ID: <20090403113058.GE31399@elte.hu> References: <20090402145455.597376000@intel.com> <20090402145702.669790000@intel.com> <20090402184514.GC843@elte.hu> <928CFBE8E7CB0040959E56B4EA41A77E9271804B@irsmsx504.ger.corp.intel.com> <928CFBE8E7CB0040959E56B4EA41A77E9271809B@irsmsx504.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <928CFBE8E7CB0040959E56B4EA41A77E9271809B@irsmsx504.ger.corp.intel.com> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1020 Lines: 31 * Metzger, Markus T wrote: > >-----Original Message----- > >From: Metzger, Markus T > >Sent: Friday, April 03, 2009 8:20 AM > >To: Ingo Molnar > > > >>Also, raw use of jiffies_64 is buggy and racy. Why does this use > >>jiffies to begin with - why not some finer grained time? > > > >What would be a good time to use? > > I found cpu_clock() declared in sched.h, which is based on TSC and > seems to be used by the scheduler, as well. Would this be a good > time to use? i'd suggest trace_clock() [which maps to cpu_clock() internally], or trace_clock_global(). See kernel/trace/trace_clock.c about the properties/tradeoffs. Since this is a user-facing ABI, trace_clock_global() looks more compelling, despite its global lock. Ingo -- 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/