From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752137AbbALMTo (ORCPT ); Mon, 12 Jan 2015 07:19:44 -0500 Received: from mga01.intel.com ([192.55.52.88]:1301 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752008AbbALMTn (ORCPT ); Mon, 12 Jan 2015 07:19:43 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,862,1389772800"; d="scan'208";a="439440241" From: Alexander Shishkin To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Robert Richter , Frederic Weisbecker , Mike Galbraith , Paul Mackerras , Stephane Eranian , Andi Kleen , kan.liang@intel.com, adrian.hunter@intel.com, markus.t.metzger@intel.com, mathieu.poirier@linaro.org, acme@infradead.org Subject: Re: [PATCH v8 12/14] x86: perf: intel_pt: Intel PT PMU driver In-Reply-To: <20150109124824.GL3337@twins.programming.kicks-ass.net> References: <1415972627-37514-1-git-send-email-alexander.shishkin@linux.intel.com> <1415972627-37514-13-git-send-email-alexander.shishkin@linux.intel.com> <20150109124824.GL3337@twins.programming.kicks-ass.net> User-Agent: Notmuch/0.17+49~gaa57e9d (http://notmuchmail.org) Emacs/24.4.1 (x86_64-pc-linux-gnu) Date: Mon, 12 Jan 2015 14:19:35 +0200 Message-ID: <87oaq4nqco.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Fri, Nov 14, 2014 at 03:43:45PM +0200, Alexander Shishkin wrote: >> +static void pt_event_stop(struct perf_event *event, int mode) >> +{ >> + struct pt *pt = this_cpu_ptr(&pt_ctx); >> + >> + ACCESS_ONCE(pt->handle_nmi) = 0; > > Why is this needed? Will the hardware still generate interrupts if you > stop the PT thing? It's meant to serialize nmi handler against the pmu:: callbacks, but now you mentioned it, it looks very much redundant. Cheers, -- Alex