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Commit c7920614 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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perf: Disallow mmap() on per-task inherited events 



Since we now have working per-task-per-cpu events for
a while, disallow mmap() on per-task inherited
events. Those things were a performance problem
anyway, and doing away with it allows us to optimize
the buffer somewhat by assuming there is only a
single writer.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent a19d35c1

kernel/perf_event.c

+8 −0
Original line number Diff line number Diff line
@@ -2593,6 +2593,14 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 
	long user_extra, extra;

	int ret = 0;



	/*

	 * Don't allow mmap() of inherited per-task counters. This would

	 * create a performance issue due to all children writing to the

	 * same buffer.

	 */

	if (event->cpu == -1 && event->attr.inherit)

		return -EINVAL;



	if (!(vma->vm_flags & VM_SHARED))

		return -EINVAL;