linux-kernel - [tip: perf/core] perf/core: Fix perf-stat / read()

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Message-ID: <174488940302.31282.13464297816136814347.tip-bot2@tip-bot2>
Date: Thu, 17 Apr 2025 11:30:03 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>,
 James Clark <james.clark@...aro.org>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Ingo Molnar <mingo@...nel.org>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: perf/core] perf/core: Fix perf-stat / read()

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

Commit-ID:     75195453f7b17ae604dc28a91f19937b1906b333
Gitweb:        https://git.kernel.org/tip/75195453f7b17ae604dc28a91f19937b1906b333
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Wed, 16 Apr 2025 20:50:27 +02:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 17 Apr 2025 13:24:49 +02:00

perf/core: Fix perf-stat / read()

In the zeal to adjust all event->state checks to include the new
REVOKED state, one adjustment was made in error. Notably it resulted
in read() on the perf filedesc to stop working for any state lower
than ERROR, specifically EXIT.

This leads to problems with (among others) perf-stat, which wants to
read the counts after a program has finished execution.

Fixes: da916e96e2de ("perf: Make perf_pmu_unregister() useable")
Reported-by: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
Reported-by: James Clark <james.clark@...aro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/20250417080725.GH38216@noisy.programming.kicks-ass.net
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2eb9cd5..e4d7a0c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6021,7 +6021,7 @@ __perf_read(struct perf_event *event, char __user *buf, size_t count)
 	 * error state (i.e. because it was pinned but it couldn't be
 	 * scheduled on to the CPU at some point).
 	 */
-	if (event->state <= PERF_EVENT_STATE_ERROR)
+	if (event->state == PERF_EVENT_STATE_ERROR)
 		return 0;
 
 	if (count < event->read_size)