From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753933AbcIHS2w (ORCPT ); Thu, 8 Sep 2016 14:28:52 -0400 Received: from mga02.intel.com ([134.134.136.20]:7226 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752507AbcIHS2u (ORCPT ); Thu, 8 Sep 2016 14:28:50 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.30,301,1470726000"; d="scan'208";a="1037192809" Message-ID: <1473359328.154359.61.camel@linux.intel.com> Subject: Re: [PATCH v2 5/8] sched,x86: Enable Turbo Boost Max Technology From: Srinivas Pandruvada To: Peter Zijlstra , Tim Chen Cc: rjw@rjwysocki.net, tglx@linutronix.de, mingo@redhat.com, bp@suse.de, x86@kernel.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Date: Thu, 08 Sep 2016 11:28:48 -0700 In-Reply-To: <20160908182215.GA10153@twins.programming.kicks-ass.net> References: <1472762024-88771-1-git-send-email-srinivas.pandruvada@linux.intel.com> <1472762024-88771-6-git-send-email-srinivas.pandruvada@linux.intel.com> <20160908075955.GS10153@twins.programming.kicks-ass.net> <20160908180928.GB23509@linux.intel.com> <20160908182215.GA10153@twins.programming.kicks-ass.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2016-09-08 at 20:22 +0200, Peter Zijlstra wrote: > On Thu, Sep 08, 2016 at 11:09:28AM -0700, Tim Chen wrote: > > > > On Thu, Sep 08, 2016 at 09:59:55AM +0200, Peter Zijlstra wrote: > > > > > > I think there's a race here, if two tasks were to write to the > > > sysctl > > > they'd both change the value before getting stuck on the mutex in > > > enable_sched_itmt(). > > > > > > One way around that is doing something like: > > > > > > > > > struct ctl_table t; > > > int val = sysctl_sched_itmt_enabled; > > > > > > t = *table; > > > t.data = &val; > > > > > > proc_dointvec_minmax(&t, ...); > > > > > > /* and update the sysctl_sched_itmt_enabled value inside the > > > mutex */ > > > enable_sched_itmi(val); > > > > Peter, > > > > Since enable_sched_itmt is only used by sched_itmt_update_handler, > > I've moved the mutex locking to sched_itmt_update_handler to > > eliminate > > the race condition in the code path you mentioned. > > That is indeed simpler. Thanks! Do we need to send v3 to include these changes? Thanks, Srinivas > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html