Messages in this thread Patch in this message | | | Date | Wed, 15 Jan 2014 11:24:45 +0100 | From | Robert Richter <> | Subject | Re: [PATCH] oprofile: check whether oprofile perf enabled in op_overflow_handler() |
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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
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