From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751435AbaAOKYx (ORCPT ); Wed, 15 Jan 2014 05:24:53 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:48064 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750705AbaAOKYu (ORCPT ); Wed, 15 Jan 2014 05:24:50 -0500 Date: Wed, 15 Jan 2014 11:24:45 +0100 From: Robert Richter To: Weng Meiling Cc: oprofile-list@lists.sf.net, linux-kernel@vger.kernel.org, Li Zefan , wangnan0@huawei.com, "zhangwei(Jovi)" , Huang Qiang Subject: Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow_handler() Message-ID: <20140115102445.GE20315@rric.localhost> References: <52B3F66D.6060707@huawei.com> <20140113084555.GU20315@rric.localhost> <52D4984B.9090600@huawei.com> <20140114150553.GC20315@rric.localhost> <52D5EC44.30101@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52D5EC44.30101@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15.01.14 10:02:44, Weng Meiling wrote: > On 2014/1/14 23:05, Robert Richter wrote: > > @@ -94,6 +98,11 @@ static int op_create_counter(int cpu, int event) > > > > per_cpu(perf_events, cpu)[event] = pevent; > > > > + /* sync perf_events with overflow handler: */ > > + smp_wmb(); > > + > > + perf_event_enable(pevent); > > + > > Should this step go before the if check:pevent->state != PERF_EVENT_STATE_ACTIVE ? > Because the attr->disabled is true, So after the perf_event_create_kernel_counter > the pevent->state is not PERF_EVENT_STATE_ACTIVE. Right, the check is a problem. We need to move it after the event was enabled. On error, we need to NULL the event, see below. -Robert --- drivers/oprofile/oprofile_perf.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/oprofile/oprofile_perf.c b/drivers/oprofile/oprofile_perf.c index d5b2732..9dfb236 100644 --- a/drivers/oprofile/oprofile_perf.c +++ b/drivers/oprofile/oprofile_perf.c @@ -38,6 +38,9 @@ static void op_overflow_handler(struct perf_event *event, int id; u32 cpu = smp_processor_id(); + /* sync perf_events with op_create_counter(): */ + smp_rmb(); + for (id = 0; id < num_counters; ++id) if (per_cpu(perf_events, cpu)[id] == event) break; @@ -68,6 +71,7 @@ static void op_perf_setup(void) attr->config = counter_config[i].event; attr->sample_period = counter_config[i].count; attr->pinned = 1; + attr->disabled = 1; } } @@ -85,16 +89,23 @@ static int op_create_counter(int cpu, int event) if (IS_ERR(pevent)) return PTR_ERR(pevent); - if (pevent->state != PERF_EVENT_STATE_ACTIVE) { - perf_event_release_kernel(pevent); - pr_warning("oprofile: failed to enable event %d " - "on CPU %d\n", event, cpu); - return -EBUSY; - } - per_cpu(perf_events, cpu)[event] = pevent; - return 0; + /* sync perf_events with overflow handler: */ + smp_wmb(); + + perf_event_enable(pevent); + + if (pevent->state == PERF_EVENT_STATE_ACTIVE) + return 0; + + perf_event_release_kernel(pevent); + per_cpu(perf_events, cpu)[event] = NULL; + + pr_warning("oprofile: failed to enable event %d on CPU %d\n", + event, cpu); + + return -EBUSY; } static void op_destroy_counter(int cpu, int event) -- 1.8.4.2