linux-kernel - [PATCH 2/2] perf metricgroup: Return error code from metricgroup__add_metric_sys_event

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Date:   Thu, 10 Jun 2021 22:33:00 +0800
From:   John Garry <john.garry@...wei.com>
To:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...hat.com>, <namhyung@...nel.org>, <irogers@...gle.com>,
        <kjain@...ux.ibm.com>
CC:     <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "John Garry" <john.garry@...wei.com>
Subject: [PATCH 2/2] perf metricgroup: Return error code from metricgroup__add_metric_sys_event_iter()

The error code is not set at all in the sys event iter function.

This may lead to an uninitialized value of "ret" in
metricgroup__add_metric() when no CPU metric is added.

Fix by properly setting the error code.

It is not necessary to init "ret" to 0 in metricgroup__add_metric(), as
if we have no CPU or sys event metric matching, then "has_match" should
be 0 and "ret" is set to -EINVAL.

However gcc cannot detect that it may not have been set after the
map_for_each_metric() loop for CPU metrics, which is strange.

Fixes: be335ec28efa8 ("perf metricgroup: Support adding metrics for system PMUs")
Signed-off-by: John Garry <john.garry@...wei.com>
---
 tools/perf/util/metricgroup.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index c456fdeae06a..d3cf2dee36c8 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -1073,16 +1073,18 @@ static int metricgroup__add_metric_sys_event_iter(struct pmu_event *pe,
 
 	ret = add_metric(d->metric_list, pe, d->metric_no_group, &m, NULL, d->ids);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = resolve_metric(d->metric_no_group,
 				     d->metric_list, NULL, d->ids);
 	if (ret)
-		return ret;
+		goto out;
 
 	*(d->has_match) = true;
 
-	return *d->ret;
+out:
+	*(d->ret) = ret;
+	return ret;
 }
 
 static int metricgroup__add_metric(const char *metric, bool metric_no_group,
-- 
2.26.2