The poll man page says POLLRDNORM is equivalent to POLLIN. For poll,
it seems that if user sets pollfd with POLLRDNORM in userspace, perf_poll
will not return until timeout even if perf_output_wakeup called, whereas POLLIN
returns.

Fixes: 76369139ceb9 ("perf: Split up buffer handling from core code")
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
---
 kernel/events/ring_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Change list:
- v1 -> v2:
    - add changelog
- v1
  https://lore.kernel.org/all/20250313051047.2436098-1-chen.dylane@linux.dev

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

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     c96fff391c095c11dc87dab35be72dee7d217cde
Gitweb:        https://git.kernel.org/tip/c96fff391c095c11dc87dab35be72dee7d217cde
Author:        Tao Chen <chen.dylane@linux.dev>
AuthorDate:    Fri, 14 Mar 2025 11:00:36 +08:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 17 Mar 2025 08:31:04 +01:00

perf/ring_buffer: Allow the EPOLLRDNORM flag for poll

The poll man page says POLLRDNORM is equivalent to POLLIN. For poll(),
it seems that if user sets pollfd with POLLRDNORM in userspace, perf_poll
will not return until timeout even if perf_output_wakeup called,
whereas POLLIN returns.

Fixes: 76369139ceb9 ("perf: Split up buffer handling from core code")
Signed-off-by: Tao Chen <chen.dylane@linux.dev>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250314030036.2543180-1-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 59a52b1..5130b11 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;