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perf/ring_buffer: Fix AUX record suppression 

The following commit:

  1627314fb5 ("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: 1627314fb5 ("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>
This commit is contained in:
Alexander Shishkin 2019-03-29 11:13:38 +02:00 committed by Ingo Molnar
parent 52a44f83fc
commit 339bc41835
1 changed files with 15 additions and 18 deletions
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33
kernel/events/ring_buffer.c
View File

@ -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))