diff options
Diffstat (limited to 'kernel/events/ring_buffer.c')
| -rw-r--r-- | kernel/events/ring_buffer.c | 14 |
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; |