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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-05-20 14:35:15 +0200
committerIngo Molnar <mingo@elte.hu>2010-05-21 11:37:57 +0200
commit0f139300c9057c16b5833a4636b715b104fe0baa (patch)
treee7b19c4fc8599fb683cee1b618b28a8aa16208e2
parent1c024eca51fdc965290acf342ae16a476c2189d0 (diff)
downloadlinux-2.6.34-ux500-0f139300c9057c16b5833a4636b715b104fe0baa.tar.gz
perf: Ensure that IOC_OUTPUT isn't used to create multi-writer buffers
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> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> LKML-Reference: <20100521090710.528215873@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/perf_event.c19
1 files changed, 19 insertions, 0 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 3f2cc313ee2..7a932526946 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4920,6 +4920,13 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
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;
@@ -4940,6 +4947,18 @@ static int perf_event_set_output(struct perf_event *event, int output_fd)
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: