perf/ring_buffer: Fix AUX record suppression

The following commit:

  c0115714e85870d ("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: c0115714e85870d ("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>

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2545ac08cc77b0bb1df9df04be353bbe6a7a0575..5eedb49a65ea2c8f6e7ea8db916b1320806df0c9 100644 (file)
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -455,24 +455,21 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size)
                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))