[PATCH 5.4 091/154] perf/ring_buffer: Allow the EPOLLRDNORM flag for poll

Greg Kroah-Hartman
2025-04-08T12:06:17Z

From: Tao Chen <chen.dylane@linux.dev>

[ Upstream commit c96fff391c095c11dc87dab35be72dee7d217cde ]

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 679cc87b40f4b..0611477e4dadd 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;
irq_work_queue(&handle->event->pending);
--
2.39.5