* [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
@ 2025-03-13 5:10 Tao Chen
2025-03-13 10:05 ` Ingo Molnar
0 siblings, 1 reply; 7+ messages in thread
From: Tao Chen @ 2025-03-13 5:10 UTC (permalink / raw)
To: peterz, mingo, acme, namhyung, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang
Cc: linux-perf-users, linux-kernel, Tao Chen
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);
handle->event->pending_wakeup = 1;
--
2.43.0
^ permalink raw reply related [flat|nested] 7+ messages in thread* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-13 5:10 [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll Tao Chen
@ 2025-03-13 10:05 ` Ingo Molnar
2025-03-13 17:03 ` Tao Chen
0 siblings, 1 reply; 7+ messages in thread
From: Ingo Molnar @ 2025-03-13 10:05 UTC (permalink / raw)
To: Tao Chen
Cc: peterz, mingo, acme, namhyung, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
* 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...
Thanks,
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-13 10:05 ` Ingo Molnar
@ 2025-03-13 17:03 ` Tao Chen
2025-03-13 17:09 ` Ingo Molnar
0 siblings, 1 reply; 7+ messages in thread
From: Tao Chen @ 2025-03-13 17:03 UTC (permalink / raw)
To: Ingo Molnar
Cc: peterz, mingo, acme, namhyung, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
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
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-13 17:03 ` Tao Chen
@ 2025-03-13 17:09 ` Ingo Molnar
2025-03-13 23:26 ` Tao Chen
2025-03-14 2:31 ` Namhyung Kim
0 siblings, 2 replies; 7+ messages in thread
From: Ingo Molnar @ 2025-03-13 17:09 UTC (permalink / raw)
To: Tao Chen
Cc: peterz, mingo, acme, namhyung, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
* Tao Chen <chen.dylane@linux.dev> wrote:
> 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.
Mind adding this to the changelog, and explain that this patch fixes
this particular poll() functionality and semantics for userspace?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-13 17:09 ` Ingo Molnar
@ 2025-03-13 23:26 ` Tao Chen
2025-03-14 2:31 ` Namhyung Kim
1 sibling, 0 replies; 7+ messages in thread
From: Tao Chen @ 2025-03-13 23:26 UTC (permalink / raw)
To: Ingo Molnar
Cc: peterz, mingo, acme, namhyung, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
在 2025/3/14 01:09, Ingo Molnar 写道:
> explain that this patch fixes
> this particular poll() functionality and semantics
will do it, thanks.
--
Best Regards
Tao Chen
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-13 17:09 ` Ingo Molnar
2025-03-13 23:26 ` Tao Chen
@ 2025-03-14 2:31 ` Namhyung Kim
2025-03-14 8:39 ` Ingo Molnar
1 sibling, 1 reply; 7+ messages in thread
From: Namhyung Kim @ 2025-03-14 2:31 UTC (permalink / raw)
To: Ingo Molnar
Cc: Tao Chen, peterz, mingo, acme, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
Hello,
On Thu, Mar 13, 2025 at 06:09:45PM +0100, Ingo Molnar wrote:
>
> * Tao Chen <chen.dylane@linux.dev> wrote:
>
> > 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.
>
> Mind adding this to the changelog, and explain that this patch fixes
> this particular poll() functionality and semantics for userspace?
Off topic, but I think it should return something (either POLLHUP or
POLLERR) when the event goes to an error state like pinned events are
not scheduled.
Thanks,
Namhyung
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll
2025-03-14 2:31 ` Namhyung Kim
@ 2025-03-14 8:39 ` Ingo Molnar
0 siblings, 0 replies; 7+ messages in thread
From: Ingo Molnar @ 2025-03-14 8:39 UTC (permalink / raw)
To: Namhyung Kim
Cc: Tao Chen, peterz, mingo, acme, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, kan.liang, linux-perf-users,
linux-kernel
* Namhyung Kim <namhyung@kernel.org> wrote:
> Hello,
>
> On Thu, Mar 13, 2025 at 06:09:45PM +0100, Ingo Molnar wrote:
> >
> > * Tao Chen <chen.dylane@linux.dev> wrote:
> >
> > > 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.
> >
> > Mind adding this to the changelog, and explain that this patch fixes
> > this particular poll() functionality and semantics for userspace?
>
> Off topic, but I think it should return something (either POLLHUP or
> POLLERR) when the event goes to an error state like pinned events are
> not scheduled.
Mind sending a patch for that?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 7+ messages in thread
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2025-03-13 5:10 [PATCH linux-next] perf/ring_buffer: Add EPOLLRDNORM flag for poll Tao Chen
2025-03-13 10:05 ` Ingo Molnar
2025-03-13 17:03 ` Tao Chen
2025-03-13 17:09 ` Ingo Molnar
2025-03-13 23:26 ` Tao Chen
2025-03-14 2:31 ` Namhyung Kim
2025-03-14 8:39 ` Ingo Molnar
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