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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-05-18 10:33:24 +0200
committerIngo Molnar <mingo@elte.hu>2010-05-18 18:35:48 +0200
commitc7920614cebbf269a7c8397ff959a8dcf727465c (patch)
treed1ca38ee77cb4160660efb97b8bdc2e5c44967c1 /kernel
parenta19d35c11fd559dd7dfd5a2078df7c9af74a5d88 (diff)
downloadlinux-2.6.34-ux500-c7920614cebbf269a7c8397ff959a8dcf727465c.tar.gz
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: 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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/perf_event.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 6ae62186dd0..ff5d430d45a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -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;