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perf: Disallow mmap() on per-task inherited events

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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: Peter 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: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-05-18 10:33:24 +02:00 committed by Ingo Molnar
parent a19d35c11f
commit c7920614ce
1 changed files with 8 additions and 0 deletions
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8
kernel/perf_event.c
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@ -2593,6 +2593,14 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
long user_extra, extra; long user_extra, extra;
int ret = 0; 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)) if (!(vma->vm_flags & VM_SHARED))
return -EINVAL; return -EINVAL;