Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755646AbZCQPQA (ORCPT ); Tue, 17 Mar 2009 11:16:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752609AbZCQPPu (ORCPT ); Tue, 17 Mar 2009 11:15:50 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:34142 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753132AbZCQPPt (ORCPT ); Tue, 17 Mar 2009 11:15:49 -0400 Date: Tue, 17 Mar 2009 16:15:36 +0100 From: Ingo Molnar To: "Metzger, Markus T" Cc: "linux-kernel@vger.kernel.org" , "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" Subject: Re: [patch 1/5] x86, bts: detect size of DS fields Message-ID: <20090317151536.GA13895@elte.hu> References: <20090313104218.A30096@sedona.ch.intel.com> <20090313110357.GC31094@elte.hu> <928CFBE8E7CB0040959E56B4EA41A77E4A663C47@irsmsx504.ger.corp.intel.com> <20090317105558.GK6477@elte.hu> <928CFBE8E7CB0040959E56B4EA41A77E4A664285@irsmsx504.ger.corp.intel.com> <20090317123442.GB22759@elte.hu> <928CFBE8E7CB0040959E56B4EA41A77E4A6642C7@irsmsx504.ger.corp.intel.com> <928CFBE8E7CB0040959E56B4EA41A77E4A6643E0@irsmsx504.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <928CFBE8E7CB0040959E56B4EA41A77E4A6643E0@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=3.2.5 -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: 1300 Lines: 41 * Metzger, Markus T wrote: > >-----Original Message----- > >From: Metzger, Markus T > >Sent: Tuesday, March 17, 2009 1:58 PM > >To: Ingo Molnar > > > >>> I think I found the problem: > >>> ds_request_bts() needs to allocate a small amount of memory. > >>> It uses GFP_KERNEL. > >>> > >>> Hw-branch-tracer essentially does on_each_cpu(ds_request_bts()). > >>> > >>> Since ds_request_bts() is meant to be called on the cpu that > >>> should be traced, it should use GFP_ATOMIC to allow calls from > >>> smp_call_function() and friends. > >>> > >>> Would that be acceptable? > >> > >>That's not really a good solution - GFP_ATOMIC is not a reliable > >>form of allocation. > > That problem also is in the .29-rc version. > It affects the hw-branch-tracer. > The ptrace interface should not be affected. > > The changes I sketched below will be too intrusive. > Do you want a small patch that turns GFP_KERNEL into GFP_ATOMIC > for .29? Yeah - but it will be for .29.1 - the hw-branch-tracer is off by default. 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/