linux-kernel - [tip: perf/urgent] perf/core: Change to POLLERR for pinned events with error

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Message-ID: <174539441547.31282.3071132411377381637.tip-bot2@tip-bot2>
Date: Wed, 23 Apr 2025 07:46:54 -0000
From: "tip-bot2 for Namhyung Kim" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Gabriel Marin <gmx@...gle.com>, Namhyung Kim <namhyung@...nel.org>,
 Ingo Molnar <mingo@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Kan Liang <kan.liang@...ux.intel.com>, Mark Rutland <mark.rutland@....com>,
 Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject:
 [tip: perf/urgent] perf/core: Change to POLLERR for pinned events with error

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@...nel.org>
AuthorDate:    Tue, 22 Apr 2025 15:33:18 -07:00
Committer:     Ingo Molnar <mingo@...nel.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@...gle.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Peter Zijlstra <peterz@...radead.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