linux-kernel - Re: [PATCH] perf stat: Fix crash on arm64

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Message-ID: <20260205175250.GC3529712@e132581.arm.com>
Date: Thu, 5 Feb 2026 17:52:50 +0000
From: Leo Yan <leo.yan@....com>
To: Ian Rogers <irogers@...gle.com>
Cc: Breno Leitao <leitao@...ian.org>, Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	James Clark <james.clark@...aro.org>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-team@...a.com, Denis Yaroshevskiy <dyaroshev@...a.com>
Subject: Re: [PATCH] perf stat: Fix crash on arm64

On Thu, Feb 05, 2026 at 05:39:18PM +0000, Leo Yan wrote:

> > > The sorting function introduced by commit a745c0831c15c ("perf stat:
> > > Sort default events/metrics") compares events based on their individual
> > > properties. This can cause events from different groups to be
> > > interleaved, resulting in group members appearing before their leaders
> > > in the sorted evlist.
> > 
> > Hi, sorry for the issue. I can see what you're saying but why is this
> > an arm64 issue? The legacy Default metrics are common to all
> > architectures:
> > https://web.git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tree/tools/perf/pmu-events/arch/common/common/metrics.json?h=perf-tools-next
> 
> Since you are mentioning common metrics, I found the common metrics does
> not work on Arm64 platform (I built with NO_JEVENTS=1 or enabled jevnts
> but both don't work).
> 
> The latest perf will have no any output if the CPU type is missed in
> json and rallback to common metrics. The failure path is:
> 
>   add_default_events()
>     metricgroup__parse_groups()
>       pmu_metrics_table__find()  => return NULL
> 
> In my case, pmu_metrics_table__find() always return NULL, as a result,
> `perf stat sleep 1` directly bail out without any output.
> 
> I expect Breno's env might have the corresponding CPU json files, this
> is possible different from my test machine.

On my local env, I need a fix:

diff --git a/tools/perf/pmu-events/empty-pmu-events.c b/tools/perf/pmu-events/empty-pmu-events.c
index e4d00f6b2b5d..f74acc206856 100644
--- a/tools/perf/pmu-events/empty-pmu-events.c
+++ b/tools/perf/pmu-events/empty-pmu-events.c
@@ -3237,14 +3237,6 @@ const struct pmu_events_table *perf_pmu__default_core_events_table(void)
         return NULL;
 }
 
-const struct pmu_metrics_table *pmu_metrics_table__find(void)
-{
-        struct perf_cpu cpu = {-1};
-        const struct pmu_events_map *map = map_for_cpu(cpu);
-
-        return map ? &map->metric_table : NULL;
-}
-
 const struct pmu_metrics_table *pmu_metrics_table__default(void)
 {
         int i = 0;
@@ -3261,6 +3253,17 @@ const struct pmu_metrics_table *pmu_metrics_table__default(void)
         return NULL;
 }
 
+const struct pmu_metrics_table *pmu_metrics_table__find(void)
+{
+        struct perf_cpu cpu = {-1};
+        const struct pmu_events_map *map = map_for_cpu(cpu);
+
+       if (map)
+               return &map->metric_table;
+
+       return pmu_metrics_table__default();
+}
+

I have no deep understanding for jevents, seems to me, Breno's issue is
a different one from me.  Please kindly confirm.

Thanks,
Leo