From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/3] perf: add context field to perf_event Date: Tue, 12 Jul 2011 12:16:40 +0300 Message-ID: <4E1C10F8.6010300@redhat.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Will Deacon , Frederic Weisbecker , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , Ingo Molnar , "acme@ghostprotocols.net" , Jason Wessel To: Peter Zijlstra Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22650 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752340Ab1GLJQ6 (ORCPT ); Tue, 12 Jul 2011 05:16:58 -0400 In-Reply-To: <1310462046.14978.11.camel@twins> Sender: kvm-owner@vger.kernel.org List-ID: On 07/12/2011 12:14 PM, Peter Zijlstra wrote: > On Tue, 2011-07-12 at 12:08 +0300, Avi Kivity wrote: > > Similar, but with stronger guarantees: when the function is called, > > current == p, and the task was either sleeping or in userspace. > > If the task is sleeping, current can never be p. The guarantee is that the task was sleeping just before the function is called. Of course it's woken up to run the function. The idea is that you run the function in a known safe point to avoid extra synchronization. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.