From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751840Ab1HYOUk (ORCPT ); Thu, 25 Aug 2011 10:20:40 -0400 Received: from casper.infradead.org ([85.118.1.10]:51034 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750994Ab1HYOUe convert rfc822-to-8bit (ORCPT ); Thu, 25 Aug 2011 10:20:34 -0400 Subject: Re: [PATCH] perf_event: fix slow and broken cgroup context switch code From: Peter Zijlstra To: Stephane Eranian Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, ming.m.lin@intel.com, Oleg Nesterov , Jiri Olsa Date: Thu, 25 Aug 2011 16:20:20 +0200 In-Reply-To: <20110825135803.GA4697@quad> References: <20110825135803.GA4697@quad> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.2- Message-ID: <1314282021.27911.12.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-08-25 at 15:58 +0200, Stephane Eranian wrote: > +static inline void perf_event_task_sched_out(struct task_struct > *prev, > + struct task_struct *next) > { > perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, NULL, 0); > > - __perf_event_task_sched_out(task, next); > + if (static_branch(&perf_sched_events)) > + __perf_event_task_sched_out(prev, next); > } Right, so the reason we removed the static branch from there is lkml.kernel.org/r/20110324164436.GC1930@jolsa.brq.redhat.com now I think the series 075e0b0085 to 64ce312618e should have cured that problem, and adding the static_branch() is now safe again. But there's no mention of any of this in the Changelog. Also, the adding back of the static_branch() is mostly unrelated to the rest of the patch, which I shall now stare at :-)