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

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Message-ID: <Z9Kt57aAC7XET7Na@gmail.com>
Date: Thu, 13 Mar 2025 11:05:27 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Tao Chen <chen.dylane@...ux.dev>
Cc: peterz@...radead.org, mingo@...hat.com, acme@...nel.org,
	namhyung@...nel.org, mark.rutland@....com,
	alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
	irogers@...gle.com, adrian.hunter@...el.com,
	kan.liang@...ux.intel.com, linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for
 poll


* Tao Chen <chen.dylane@...ux.dev> wrote:

> The poll man page says POLLRDNORM is equivalent to POLLIN,
> so add EPOLLRDNORM here.
> 
> Signed-off-by: Tao Chen <chen.dylane@...ux.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...

Thanks,

	Ingo