From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752188Ab1GLJgZ (ORCPT ); Tue, 12 Jul 2011 05:36:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:14521 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751140Ab1GLJgX (ORCPT ); Tue, 12 Jul 2011 05:36:23 -0400 Message-ID: <4E1C1585.4000207@redhat.com> Date: Tue, 12 Jul 2011 12:36:05 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Peter Zijlstra CC: Will Deacon , Frederic Weisbecker , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , Ingo Molnar , "acme@ghostprotocols.net" , Jason Wessel Subject: Re: [PATCH 1/3] perf: add context field to perf_event References: <1309362157-6596-1-git-send-email-avi@redhat.com> <1309362157-6596-2-git-send-email-avi@redhat.com> <20110629160841.GA2032@somewhere> <20110629162725.GH15521@e102144-lin.cambridge.arm.com> <20110704135820.GD5551@somewhere> <4E11C9CC.2070909@redhat.com> <20110704143655.GE5551@somewhere> <20110711210753.GA3582@e102144-lin.cambridge.arm.com> <4E1BF5A1.5070301@redhat.com> <1310459898.18678.108.camel@twins> <4E1C0F02.9040906@redhat.com> <1310462046.14978.11.camel@twins> <4E1C10F8.6010300@redhat.com> <1310462335.14978.12.camel@twins> <4E1C1373.5080500@redhat.com> <1310463060.14978.17.camel@twins> In-Reply-To: <1310463060.14978.17.camel@twins> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/12/2011 12:31 PM, Peter Zijlstra wrote: > > > > But it means that 'current' is not set to the right value. If the > > function depends on it, then it will misbehave. And in fact > > preempt_notifier_register(), which is the function we want to call here, > > does depend on current. > > > > Of course we need to find more users for this, but I have a feeling this > > will be generally useful. The alternative is to keep adding bits to > > thread_info::flags. > > Using TIF_bits sounds like a much better solution for this, wakeups are > really rather expensive and its best to avoid extra if at all possible. > We do need a way to make the task look at them. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.