Commit 59741451 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

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



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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250812104019.956479989@infradead.org
parent d23a6dbc

kernel/events/core.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

}