The commit f4b07fd62d4d11d5 ("perf/core: Use POLLHUP for pinned events
in error") started to emit POLLHUP for pinned events in an error state.

But the POLLHUP is also used to signal events that the attached task is
terminated.  To distinguish pinned per-task events in the error state
it would need to check if the task is live.

If we can change it to POLLERR it should be clear.

Suggested-by: Gabriel Marin <gmx@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
---
 kernel/events/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e93c195659140d30..95e703891b24f8fc 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3943,7 +3943,7 @@ static int merge_sched_in(struct perf_event *event, void *data)
 			perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
 
 			if (*perf_event_fasync(event))
-				event->pending_kill = POLL_HUP;
+				event->pending_kill = POLL_ERR;
 
 			perf_event_wakeup(event);
 		} else {
@@ -6075,7 +6075,7 @@ static __poll_t perf_poll(struct file *file, poll_table *wait)
 
 	if (unlikely(READ_ONCE(event->state) == PERF_EVENT_STATE_ERROR &&
 		     event->attr.pinned))
-		return events;
+		return EPOLLERR;
 
 	/*
 	 * Pin the event->rb by taking event->mmap_mutex; otherwise
-- 
2.49.0.805.g082f7c87e0-goog

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

Commit-ID:     0db61388b389f43c1ba2f1cee3613feb4fd12150
Gitweb:        https://git.kernel.org/tip/0db61388b389f43c1ba2f1cee3613feb4fd12150
Author:        Namhyung Kim <namhyung@kernel.org>
AuthorDate:    Tue, 22 Apr 2025 15:33:18 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 23 Apr 2025 09:39:06 +02:00

perf/core: Change to POLLERR for pinned events with error

Commit:

  f4b07fd62d4d11d5 ("perf/core: Use POLLHUP for pinned events in error")

started to emit POLLHUP for pinned events in an error state.

But the POLLHUP is also used to signal events that the attached task is
terminated.  To distinguish pinned per-task events in the error state
it would need to check if the task is live.

Change it to POLLERR to make it clear.

Suggested-by: Gabriel Marin <gmx@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250422223318.180343-1-namhyung@kernel.org
---
 kernel/events/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index e93c195..95e7038 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3943,7 +3943,7 @@ static int merge_sched_in(struct perf_event *event, void *data)
 			perf_event_set_state(event, PERF_EVENT_STATE_ERROR);
 
 			if (*perf_event_fasync(event))
-				event->pending_kill = POLL_HUP;
+				event->pending_kill = POLL_ERR;
 
 			perf_event_wakeup(event);
 		} else {
@@ -6075,7 +6075,7 @@ static __poll_t perf_poll(struct file *file, poll_table *wait)
 
 	if (unlikely(READ_ONCE(event->state) == PERF_EVENT_STATE_ERROR &&
 		     event->attr.pinned))
-		return events;
+		return EPOLLERR;
 
 	/*
 	 * Pin the event->rb by taking event->mmap_mutex; otherwise