Patch "perf stat: Fix bug in handling events in error state" has been added to the 4.9-stable tree

Patch "perf stat: Fix bug in handling events in error state" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    perf stat: Fix bug in handling events in error state

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-stat-fix-bug-in-handling-events-in-error-state.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Sun Mar 18 16:55:33 CET 2018
From: Stephane Eranian <eranian@google.com>
Date: Wed, 12 Apr 2017 11:23:01 -0700
Subject: perf stat: Fix bug in handling events in error state

From: Stephane Eranian <eranian@google.com>


[ Upstream commit db49a71798a38f3ddf3f3462703328dca39b1ac7 ]

(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: Stephane Eranian <eranian@google.com>
Reviewed-by: David Carrillo-Cisneros <davidcc@google.com>
Acked-by: Jiri 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: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/perf/builtin-stat.c |   12 +++++++++---
 tools/perf/util/evsel.c   |    4 ++--
 2 files changed, 11 insertions(+), 5 deletions(-)

--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -311,8 +311,12 @@ static int read_counter(struct perf_evse
 			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)) {
@@ -337,12 +341,14 @@ static int read_counter(struct perf_evse
 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);
 	}
 }
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1221,7 +1221,7 @@ int perf_evsel__read(struct perf_evsel *
 	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;
@@ -1239,7 +1239,7 @@ int __perf_evsel__read_on_cpu(struct per
 	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);


Patches currently in stable-queue which might be from eranian@google.com are

queue-4.9/perf-session-don-t-rely-on-evlist-in-pipe-mode.patch
queue-4.9/perf-tools-make-perf_event__synthesize_mmap_events-scale.patch
queue-4.9/perf-inject-copy-events-when-reordering-events-in-pipe-mode.patch
queue-4.9/perf-stat-fix-bug-in-handling-events-in-error-state.patch