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perf: Identify the 0->1 transition for event::mmap_count

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

Specifically, this is the case where we've created the RB, this means
there was no RB, and as such there could not have been an mmap.
Additionally we hold mmap_mutex to serialize everything.

This must be the first.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250812104019.956479989@infradead.org
This commit is contained in:
Peter Zijlstra 2025-08-12 12:39:12 +02:00
parent d23a6dbc0a
commit 59741451b4
1 changed files with 1 additions and 1 deletions
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2
kernel/events/core.c
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@ -7034,7 +7034,7 @@ static int perf_mmap_rb(struct vm_area_struct *vma, struct perf_event *event,
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;
}