Commit 8b464eac authored Mar 17, 2022 by Ian Rogers Committed by Arnaldo Carvalho de Melo Mar 18, 2022

perf evlist: Avoid iteration for empty evlist.

As seen with 'perf stat --null ..' and reported in:
https://lore.kernel.org/lkml/YjCLcpcX2peeQVCH@kernel.org/



v2. Avoids setting evsel in the empty list case as suggested by Jiri Olsa.

    Committer testing:

Before:

  $  perf stat --null sleep 1
  Segmentation fault (core dumped)
  $

After:

  $  perf stat --null sleep 1

   Performance counter stats for 'sleep 1':

         1.010340646 seconds time elapsed

         0.001420000 seconds user
         0.000000000 seconds sys
  $

Fixes: 472832d2 ("perf evlist: Refactor evlist__for_each_cpu()")
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20220317231643.550902-1-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

parent 3cf6a32f

tools/perf/util/evlist.c

+17 −11

Original line number	Diff line number	Diff line
		@@ -346,7 +346,7 @@ struct evlist_cpu_iterator evlist__cpu_begin(struct evlist *evlist, struct affin
		{
		struct evlist_cpu_iterator itr = {
		.container = evlist,
		.evsel = evlist__first(evlist),
		.evsel = NULL,
		.cpu_map_idx = 0,
		.evlist_cpu_map_idx = 0,
		.evlist_cpu_map_nr = perf_cpu_map__nr(evlist->core.all_cpus),
		@@ -354,17 +354,23 @@ struct evlist_cpu_iterator evlist__cpu_begin(struct evlist *evlist, struct affin
		.affinity = affinity,
		};

		if (evlist__empty(evlist)) {
		/* Ensure the empty list doesn't iterate. */
		itr.evlist_cpu_map_idx = itr.evlist_cpu_map_nr;
		} else {
		itr.evsel = evlist__first(evlist);
		if (itr.affinity) {
		itr.cpu = perf_cpu_map__cpu(evlist->core.all_cpus, 0);
		affinity__set(itr.affinity, itr.cpu.cpu);
		itr.cpu_map_idx = perf_cpu_map__idx(itr.evsel->core.cpus, itr.cpu);
		/*
		* If this CPU isn't in the evsel's cpu map then advance through
		* the list.
		* If this CPU isn't in the evsel's cpu map then advance
		* through the list.
		*/
		if (itr.cpu_map_idx == -1)
		evlist_cpu_iterator__next(&itr);
		}
		}
		return itr;
		}