diff options
| author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-03-17 17:32:29 -0400 |
|---|---|---|
| committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2020-03-19 19:11:20 -0400 |
| commit | 153368ce1bd0ccb47812a3185e824445a7024ea5 (patch) | |
| tree | 1733d0e1eeb0611c99aa07bd96b697a03b00d198 | |
| parent | ff84c50cfb4b8dc68c982fb6c05a524e1539ee2f (diff) | |
ring-buffer: Optimize rb_iter_head_event()
As it is fine to perform several "peeks" of event data in the ring buffer
via the iterator before moving it forward, do not re-read the event, just
return what was read before. Otherwise, it can cause inconsistent results,
especially when testing multiple CPU buffers to interleave them.
Link: http://lkml.kernel.org/r/20200317213416.592032170@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
| -rw-r--r-- | kernel/trace/ring_buffer.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 475338fda969..5979327254f9 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1929,6 +1929,9 @@ rb_iter_head_event(struct ring_buffer_iter *iter) unsigned long commit; unsigned length; + if (iter->head != iter->next_event) + return iter->event; + /* * When the writer goes across pages, it issues a cmpxchg which * is a mb(), which will synchronize with the rmb here. |