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perf/core: Disable the event on a truncated AUX record

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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 <[email protected]>
Signed-off-by: Alexander Shishkin <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/1462886313-13660-3-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Alexander Shishkin 2016-05-10 16:18:33 +03:00 • committed by Ingo Molnar
commit 3f56e687a1
1 changed files with 9 additions and 1 deletions
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10
kernel/events/ring_buffer.c
View file

@ -405,6 +405,7 @@ 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;
@ -433,9 +434,16 @@ 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);