Re: [PATCH] perf: Do not check PERF_EVENT_STATE_EXIT on syscall read path

[Stephane Eranian]

Peter,



On Mon, Sep 8, 2014 at 5:22 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, Sep 08, 2014 at 04:31:07PM +0200, Jiri Olsa wrote:
>> Revert PERF_EVENT_STATE_EXIT check on read syscall path.
>> It breaks standard way to read counter, which is to open
>> the counter, wait for the monitored process to die and
>> read the counter.
>>
>> Reported-by: Stephane Eranian <eranian@xxxxxxxxxx>
>> Acked-by: Stephane Eranian <eranian@xxxxxxxxxx>
>> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
>> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>> Cc: Paul Mackerras <paulus@xxxxxxxxx>
>> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
>> Cc: Stephane Eranian <eranian@xxxxxxxxxx>
>> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
>
> Thanks!
Still don't see this fix in tip.git.

>> ---
>>  kernel/events/core.c | 3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index d8cb4d21a346..6d1c9ce1643e 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -3600,8 +3600,7 @@ perf_read_hw(struct perf_event *event, char __user *buf, size_t count)
>>        * error state (i.e. because it was pinned but it couldn't be
>>        * scheduled on to the CPU at some point).
>>        */
>> -     if ((event->state == PERF_EVENT_STATE_ERROR) ||
>> -         (event->state == PERF_EVENT_STATE_EXIT))
>> +     if (event->state == PERF_EVENT_STATE_ERROR)
>>               return 0;
>>
>>       if (count < event->read_size)
>> --
>> 1.8.3.1
>>
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