Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll

[Tao Chen <chen.dylane@linux.dev>]

在 2025/3/13 18:05, Ingo Molnar 写道:
> 
> * Tao Chen <chen.dylane@linux.dev> wrote:
> 
>> The poll man page says POLLRDNORM is equivalent to POLLIN,
>> so add EPOLLRDNORM here.
>>
>> Signed-off-by: Tao Chen <chen.dylane@linux.dev>
>> ---
>>   kernel/events/ring_buffer.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
>> index 59a52b1a1..5130b119d 100644
>> --- a/kernel/events/ring_buffer.c
>> +++ b/kernel/events/ring_buffer.c
>> @@ -19,7 +19,7 @@
>>   
>>   static void perf_output_wakeup(struct perf_output_handle *handle)
>>   {
>> -	atomic_set(&handle->rb->poll, EPOLLIN);
>> +	atomic_set(&handle->rb->poll, EPOLLIN | EPOLLRDNORM);
> 
> So what does EPOLLRDNORM mean to begin with? There doesn't seem to be
> separate/specific handling of it anywhere in the kernel that I can
> see...
> 

It seems that if user set pollfd with POLLRDNORM, perf_poll will not 
return until timeout even if perf_output_wakeup called, whereas POLLIN 
returns.

> Thanks,
> 
> 	Ingo


-- 
Best Regards
Tao Chen