Re: [PATCH v1 4/4] libperf evlist: Recompute CPU map when an evsel goes system wide

[James Clark <james.clark@linaro.org>]

On 27/10/2026 17:04, Ian Rogers wrote:
> perf_evlist__go_system_wide() marks the evsel as system wide and then
> propagates the evlist's maps to it. __perf_evlist__propagate_maps()
> only assigns the PMU CPUs to evsel->cpus if the map is empty, but an
> evsel added after the evlist's maps were created already has the user
> requested CPUs propagated (e.g. the "any CPU" map of -1 in per-thread
> or workload mode). Going system wide then leaves the evsel opened on
> the wrong CPUs.
> 
> Drop the existing CPU map before propagating so the evsel is given all
> of its PMU's CPUs, as is expected for a system wide event.
> 
> Fixes: 811082e4b668 ("perf parse-events: Support user CPUs mixed with threads/processes")
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>   tools/lib/perf/evlist.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/lib/perf/evlist.c b/tools/lib/perf/evlist.c
> index c1c5b0684eed..46de69aa5a86 100644
> --- a/tools/lib/perf/evlist.c
> +++ b/tools/lib/perf/evlist.c
> @@ -835,7 +835,10 @@ void perf_evlist__go_system_wide(struct perf_evlist *evlist, struct perf_evsel *
>   {
>   	if (!evsel->system_wide) {
>   		evsel->system_wide = true;
> -		if (evlist->needs_map_propagation)
> +		if (evlist->needs_map_propagation) {
> +			perf_cpu_map__put(evsel->cpus);
> +			evsel->cpus = NULL;
>   			__perf_evlist__propagate_maps(evlist, evsel);
> +		}
>   	}
>   }

Reviewed-by: James Clark <james.clark@linaro.org>