linux-kernel - [PATCH v3 14/15] perf: Identify the 0->1 transition for event::mmap

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Message-ID: <20250812104019.956479989@infradead.org>
Date: Tue, 12 Aug 2025 12:39:12 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: tglx@...utronix.de
Cc: linux-kernel@...r.kernel.org,
 peterz@...radead.org,
 torvalds@...uxfoundation.org,
 mingo@...nel.org,
 namhyung@...nel.org,
 acme@...hat.com,
 kees@...nel.org
Subject: [PATCH v3 14/15] perf: Identify the 0->1 transition for event::mmap_count

Needed because refcount_inc() doesn't allow the 0->1 transition.

Suggested-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/events/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7033,7 +7033,7 @@ static int perf_mmap_rb(struct vm_area_s
 	perf_event_update_userpage(event);
 
 	perf_mmap_account(vma, user_extra, extra);
-	atomic_inc(&event->mmap_count);
+	atomic_set(&event->mmap_count, 1);
 
 	return 0;
 }