Messages in this thread Patch in this message | | | Date | Fri, 21 May 2010 11:02:04 +0200 | From | Peter Zijlstra <> | Subject | [PATCH 03/10] perf: Ensure IOC_OUTPUT isnt used to create multi-writer buffers |
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Since we want to ensure buffers only have a single writer, we must avoid creating one with multiple.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- kernel/perf_event.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)
Index: linux-2.6/kernel/perf_event.c =================================================================== --- linux-2.6.orig/kernel/perf_event.c +++ linux-2.6/kernel/perf_event.c @@ -4885,6 +4885,13 @@ static int perf_event_set_output(struct int fput_needed = 0; int ret = -EINVAL; + /* + * Don't allow output of inherited per-task events. This would + * create performance issues due to cross cpu access. + */ + if (event->cpu == -1 && event->attr.inherit) + return -EINVAL; + if (!output_fd) goto set; @@ -4905,6 +4912,18 @@ static int perf_event_set_output(struct if (event->data) goto out; + /* + * Don't allow cross-cpu buffers + */ + if (output_event->cpu != event->cpu) + goto out; + + /* + * If its not a per-cpu buffer, it must be the same task. + */ + if (output_event->cpu == -1 && output_event->ctx != event->ctx) + goto out; + atomic_long_inc(&output_file->f_count); set:
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