From c7920614cebbf269a7c8397ff959a8dcf727465c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 18 May 2010 10:33:24 +0200 Subject: 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 Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker LKML-Reference: Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 8 ++++++++ 1 file changed, 8 insertions(+) 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; -- cgit v1.2.3