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-rw-r--r--kernel/events/ring_buffer.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 5d3cf407e374..4a9937076331 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -459,10 +459,20 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
if (size || handle->aux_flags) {
/*
* Only send RECORD_AUX if we have something useful to communicate
+ *
+ * Note: the OVERWRITE records by themselves are not considered
+ * useful, as they don't communicate any *new* information,
+ * aside from the short-lived offset, that becomes history at
+ * the next event sched-in and therefore isn't useful.
+ * The userspace that needs to copy out AUX data in overwrite
+ * mode should know to use user_page::aux_head for the actual
+ * offset. So, from now on we don't output AUX records that
+ * have *only* OVERWRITE flag set.
*/
- perf_event_aux_event(handle->event, aux_head, size,
- handle->aux_flags);
+ if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)
+ perf_event_aux_event(handle->event, aux_head, size,
+ handle->aux_flags);
}
rb->user_page->aux_head = rb->aux_head;