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author | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2016-05-10 16:18:33 +0300 |
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committer | Sasha Levin <sasha.levin@oracle.com> | 2016-05-17 13:43:10 -0400 |
commit | 6f24160677ab5a2783b7f1f2ea5c2a23526d494e (patch) | |
tree | 3159a65a155ebb5b98813baed555dcee6d39b05b | |
parent | e5c1c3a557c8412a9afe7bc346976e93de95c1c5 (diff) | |
download | lwn-6f24160677ab5a2783b7f1f2ea5c2a23526d494e.tar.gz lwn-6f24160677ab5a2783b7f1f2ea5c2a23526d494e.zip |
perf/core: Disable the event on a truncated AUX record
[ Upstream commit 9f448cd3cbcec8995935e60b27802ae56aac8cc0 ]
When the PMU driver reports a truncated AUX record, it effectively means
that there is no more usable room in the event's AUX buffer (even though
there may still be some room, so that perf_aux_output_begin() doesn't take
action). At this point the consumer still has to be woken up and the event
has to be disabled, otherwise the event will just keep spinning between
perf_aux_output_begin() and perf_aux_output_end() until its context gets
unscheduled.
Again, for cpu-wide events this means never, so once in this condition,
they will be forever losing data.
Fix this by disabling the event and waking up the consumer in case of a
truncated AUX record.
Reported-by: Markus Metzger <markus.t.metzger@intel.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@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
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>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/1462886313-13660-3-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
-rw-r--r-- | kernel/events/ring_buffer.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 7f63ad978cb8..dba8894d25cc 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -347,6 +347,7 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size, bool truncated) { struct ring_buffer *rb = handle->rb; + bool wakeup = truncated; unsigned long aux_head; u64 flags = 0; @@ -375,9 +376,16 @@ void perf_aux_output_end(struct perf_output_handle *handle, unsigned long size, aux_head = rb->user_page->aux_head = local_read(&rb->aux_head); if (aux_head - local_read(&rb->aux_wakeup) >= rb->aux_watermark) { - perf_output_wakeup(handle); + wakeup = true; local_add(rb->aux_watermark, &rb->aux_wakeup); } + + if (wakeup) { + if (truncated) + handle->event->pending_disable = 1; + perf_output_wakeup(handle); + } + handle->event = NULL; local_set(&rb->aux_nest, 0); |