linux-kernel - Re: [PATCH v8 1/6] Revert "perf tool_pmu: More accurately set the cpus for tool events"

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Message-ID: <CAP-5=fWNygdxXtiuZyoKcWU7cJ5K9Ad8dZ1ABXC+qkBrsfqZYg@mail.gmail.com>
Date: Mon, 9 Feb 2026 15:10:36 -0800
From: Ian Rogers <irogers@...gle.com>
To: acme@...nel.org
Cc: adrian.hunter@...el.com, ak@...ux.intel.com, 
	alexander.shishkin@...ux.intel.com, andres@...razel.de, 
	dapeng1.mi@...ux.intel.com, james.clark@...aro.org, jolsa@...nel.org, 
	linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, 
	linux@...blig.org, mingo@...hat.com, namhyung@...nel.org, 
	peterz@...radead.org, thomas.falcon@...el.com, tmricht@...ux.ibm.com, 
	yang.lee@...ux.alibaba.com
Subject: Re: [PATCH v8 1/6] Revert "perf tool_pmu: More accurately set the
 cpus for tool events"

On Fri, Feb 6, 2026 at 2:25 PM Ian Rogers <irogers@...gle.com> wrote:
>
> This reverts commit d8d8a0b3603a9a8fa207cf9e4f292e81dc5d1008.
>
> The setting of a user CPU map can cause an empty intersection when
> combined with CPU 0 and the event removed. This later triggers a segv
> in the stat-shadow logic. Let's put back a full online CPU map for now
> by reverting this patch.
>
> Reported-by: Andres Freund <andres@...razel.de>
> Closes: https://lore.kernel.org/linux-perf-users/cgja46br2smmznxs7kbeabs6zgv3b4olfqgh2fdp5mxk2yom4v@w6jjgov6hdi6/
> Signed-off-by: Ian Rogers <irogers@...gle.com>

The additional stat test coverage in:
https://lore.kernel.org/lkml/aYUO0_ccQG2AnZ3V@x1/
has been merged, but without this revert the test is segfaulting.

Thanks,
Ian

> ---
>  tools/perf/util/parse-events.c |  9 ++-------
>  tools/perf/util/tool_pmu.c     | 19 -------------------
>  tools/perf/util/tool_pmu.h     |  1 -
>  3 files changed, 2 insertions(+), 27 deletions(-)
>
> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
> index d4647ded340f..f631bf7a919f 100644
> --- a/tools/perf/util/parse-events.c
> +++ b/tools/perf/util/parse-events.c
> @@ -30,7 +30,6 @@
>  #include "util/event.h"
>  #include "util/bpf-filter.h"
>  #include "util/stat.h"
> -#include "util/tool_pmu.h"
>  #include "util/util.h"
>  #include "tracepoint.h"
>  #include <api/fs/tracing_path.h>
> @@ -230,12 +229,8 @@ __add_event(struct list_head *list, int *idx,
>         if (pmu) {
>                 is_pmu_core = pmu->is_core;
>                 pmu_cpus = perf_cpu_map__get(pmu->cpus);
> -               if (perf_cpu_map__is_empty(pmu_cpus)) {
> -                       if (perf_pmu__is_tool(pmu))
> -                               pmu_cpus = tool_pmu__cpus(attr);
> -                       else
> -                               pmu_cpus = cpu_map__online();
> -               }
> +               if (perf_cpu_map__is_empty(pmu_cpus))
> +                       pmu_cpus = cpu_map__online();
>         } else {
>                 is_pmu_core = (attr->type == PERF_TYPE_HARDWARE ||
>                                attr->type == PERF_TYPE_HW_CACHE);
> diff --git a/tools/perf/util/tool_pmu.c b/tools/perf/util/tool_pmu.c
> index 37c4eae0bef1..6a9df3dc0e07 100644
> --- a/tools/perf/util/tool_pmu.c
> +++ b/tools/perf/util/tool_pmu.c
> @@ -2,7 +2,6 @@
>  #include "cgroup.h"
>  #include "counts.h"
>  #include "cputopo.h"
> -#include "debug.h"
>  #include "evsel.h"
>  #include "pmu.h"
>  #include "print-events.h"
> @@ -14,7 +13,6 @@
>  #include <api/fs/fs.h>
>  #include <api/io.h>
>  #include <internal/threadmap.h>
> -#include <perf/cpumap.h>
>  #include <perf/threadmap.h>
>  #include <fcntl.h>
>  #include <strings.h>
> @@ -111,23 +109,6 @@ const char *evsel__tool_pmu_event_name(const struct evsel *evsel)
>         return tool_pmu__event_to_str(evsel->core.attr.config);
>  }
>
> -struct perf_cpu_map *tool_pmu__cpus(struct perf_event_attr *attr)
> -{
> -       static struct perf_cpu_map *cpu0_map;
> -       enum tool_pmu_event event = (enum tool_pmu_event)attr->config;
> -
> -       if (event <= TOOL_PMU__EVENT_NONE || event >= TOOL_PMU__EVENT_MAX) {
> -               pr_err("Invalid tool PMU event config %llx\n", attr->config);
> -               return NULL;
> -       }
> -       if (event == TOOL_PMU__EVENT_USER_TIME || event == TOOL_PMU__EVENT_SYSTEM_TIME)
> -               return cpu_map__online();
> -
> -       if (!cpu0_map)
> -               cpu0_map = perf_cpu_map__new_int(0);
> -       return perf_cpu_map__get(cpu0_map);
> -}
> -
>  static bool read_until_char(struct io *io, char e)
>  {
>         int c;
> diff --git a/tools/perf/util/tool_pmu.h b/tools/perf/util/tool_pmu.h
> index ea343d1983d3..f1714001bc1d 100644
> --- a/tools/perf/util/tool_pmu.h
> +++ b/tools/perf/util/tool_pmu.h
> @@ -46,7 +46,6 @@ bool tool_pmu__read_event(enum tool_pmu_event ev,
>  u64 tool_pmu__cpu_slots_per_cycle(void);
>
>  bool perf_pmu__is_tool(const struct perf_pmu *pmu);
> -struct perf_cpu_map *tool_pmu__cpus(struct perf_event_attr *attr);
>
>  bool evsel__is_tool(const struct evsel *evsel);
>  enum tool_pmu_event evsel__tool_event(const struct evsel *evsel);
> --
> 2.53.0.rc2.204.g2597b5adb4-goog
>