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perf intel-pt: Fix snapshot overlap detection decoder errors
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Fix occasional decoder errors decoding trace data collected in snapshot
mode.

Snapshot mode can take successive snapshots of trace which might overlap.
The decoder checks whether there is an overlap but only looks at the
current and previous buffer. However buffers that do not contain
synchronization (i.e. PSB) packets cannot be decoded or used for overlap
checking. That means the decoder actually needs to check overlaps between
the current buffer and the previous buffer that contained usable data.
Make that change.

Signed-off-by: Adrian Hunter <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Poirier <[email protected]>
Cc: [email protected] # v4.3+
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
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ahunter6 authored and acmel committed Sep 29, 2016
1 parent f965520 commit 810c398
Showing 1 changed file with 11 additions and 4 deletions.
15 changes: 11 additions & 4 deletions tools/perf/util/intel-pt.c
Original file line number Diff line number Diff line change
@@ -241,7 +241,7 @@ static int intel_pt_get_trace(struct intel_pt_buffer *b, void *data)
}

queue = &ptq->pt->queues.queue_array[ptq->queue_nr];

next:
buffer = auxtrace_buffer__next(queue, buffer);
if (!buffer) {
if (old_buffer)
@@ -264,9 +264,6 @@ static int intel_pt_get_trace(struct intel_pt_buffer *b, void *data)
intel_pt_do_fix_overlap(ptq->pt, old_buffer, buffer))
return -ENOMEM;

if (old_buffer)
auxtrace_buffer__drop_data(old_buffer);

if (buffer->use_data) {
b->len = buffer->use_size;
b->buf = buffer->use_data;
@@ -276,6 +273,16 @@ static int intel_pt_get_trace(struct intel_pt_buffer *b, void *data)
}
b->ref_timestamp = buffer->reference;

/*
* If in snapshot mode and the buffer has no usable data, get next
* buffer and again check overlap against old_buffer.
*/
if (ptq->pt->snapshot_mode && !b->len)
goto next;

if (old_buffer)
auxtrace_buffer__drop_data(old_buffer);

if (!old_buffer || ptq->pt->sampling_mode || (ptq->pt->snapshot_mode &&
!buffer->consecutive)) {
b->consecutive = false;

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