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Subject[PATCH 5.0 111/115] perf/ring_buffer: Fix AUX record suppression
Date
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>

commit 339bc4183596e1f68c2c98a03b87aa124107c317 upstream.

The following commit:

1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")

has an unintended side-effect of also suppressing all AUX records with no flags
and non-zero size, so all the regular records in the full trace mode.
This breaks some use cases for people.

Fix this by restoring "regular" AUX records.

Reported-by: Ben Gainey <Ben.Gainey@arm.com>
Tested-by: Ben Gainey <Ben.Gainey@arm.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 1627314fb54a33e ("perf: Suppress AUX/OVERWRITE records")
Link: https://lkml.kernel.org/r/20190329091338.29999-1-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/events/ring_buffer.c | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)

--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -456,24 +456,21 @@ void perf_aux_output_end(struct perf_out
rb->aux_head += 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.
- */
-
- if (handle->aux_flags & ~(u64)PERF_AUX_FLAG_OVERWRITE)
- perf_event_aux_event(handle->event, aux_head, 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.
+ */
+ if (size || (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;
if (rb_need_aux_wakeup(rb))

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