Commit db49a717 authored by Stephane Eranian's avatar Stephane Eranian Committed by Arnaldo Carvalho de Melo
Browse files

perf stat: Fix bug in handling events in error state 



(This is a patch has been sitting in the Intel CQM/CMT driver series for
 a while, despite not depend on it. Sending it now independently since
 the series is being discarded.)

When an event is in error state, read() returns 0 instead of sizeof()
buffer. In certain modes, such as interval printing, ignoring the 0
return value may cause bogus count deltas to be computed and thus
invalid results printed.

This patch fixes this problem by modifying read_counters() to mark the
event as not scaled (scaled = -1) to force the printout routine to show
<NOT COUNTED>.

Signed-off-by: default avatarStephane Eranian <eranian@google.com>
Reviewed-by: default avatarDavid Carrillo-Cisneros <davidcc@google.com>
Acked-by: default avatarJiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20170412182301.44406-1-davidcc@google.com


Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 7be6b316

tools/perf/builtin-stat.c

+9 −3
Original line number Diff line number Diff line
@@ -312,8 +312,12 @@ static int read_counter(struct perf_evsel *counter) 
			struct perf_counts_values *count;



			count = perf_counts(counter->counts, cpu, thread);

			if (perf_evsel__read(counter, cpu, thread, count))

			if (perf_evsel__read(counter, cpu, thread, count)) {

				counter->counts->scaled = -1;

				perf_counts(counter->counts, cpu, thread)->ena = 0;

				perf_counts(counter->counts, cpu, thread)->run = 0;

				return -1;

			}



			if (STAT_RECORD) {

				if (perf_evsel__write_stat_event(counter, cpu, thread, count)) {
@@ -338,12 +342,14 @@ static int read_counter(struct perf_evsel *counter) 
static void read_counters(void)

{

	struct perf_evsel *counter;

	int ret;



	evlist__for_each_entry(evsel_list, counter) {

		if (read_counter(counter))

		ret = read_counter(counter);

		if (ret)

			pr_debug("failed to read counter %s\n", counter->name);



		if (perf_stat_process_counter(&stat_config, counter))

		if (ret == 0 && perf_stat_process_counter(&stat_config, counter))

			pr_warning("failed to process counter %s\n", counter->name);

	}

}

tools/perf/util/evsel.c

+2 −2
Original line number Diff line number Diff line
@@ -1239,7 +1239,7 @@ int perf_evsel__read(struct perf_evsel *evsel, int cpu, int thread, 
	if (FD(evsel, cpu, thread) < 0)

		return -EINVAL;



	if (readn(FD(evsel, cpu, thread), count, sizeof(*count)) < 0)

	if (readn(FD(evsel, cpu, thread), count, sizeof(*count)) <= 0)

		return -errno;



	return 0;
@@ -1257,7 +1257,7 @@ int __perf_evsel__read_on_cpu(struct perf_evsel *evsel, 
	if (evsel->counts == NULL && perf_evsel__alloc_counts(evsel, cpu + 1, thread + 1) < 0)

		return -ENOMEM;



	if (readn(FD(evsel, cpu, thread), &count, nv * sizeof(u64)) < 0)

	if (readn(FD(evsel, cpu, thread), &count, nv * sizeof(u64)) <= 0)

		return -errno;



	perf_evsel__compute_deltas(evsel, cpu, thread, &count);

CRA Git | Maintained and supported by SUSTech CRA and CCSE