linux-kernel - Re: [PATCH] perf: ignore exited thread when synthesize thread map

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Date:   Wed, 22 Nov 2023 13:05:24 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Cruz Zhao <CruzZhao@...ux.alibaba.com>
Cc:     mingo@...hat.com, peterz@...radead.org, acme@...nel.org,
        mark.rutland@....com, alexander.shishkin@...ux.intel.com,
        jolsa@...nel.org, irogers@...gle.com, adrian.hunter@...el.com,
        kprateek.nayak@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf: ignore exited thread when synthesize thread map

Hello,

On Tue, Nov 21, 2023 at 6:22 PM Cruz Zhao <CruzZhao@...ux.alibaba.com> wrote:
>
> When synthesize thread map, some threads in thread map may have
> already exited, so that __event__synthesize_thread() returns -1
> and the synthesis breaks. However, It will not have any effect
> if we just ignore the exited thread. So just ignore it and continue.

Looks ok.  But I guess you want to do the same for the leader
thread below as well.

Thanks,
Namhyung

>
> Signed-off-by: Cruz Zhao <CruzZhao@...ux.alibaba.com>
> ---
>  tools/perf/util/synthetic-events.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/synthetic-events.c b/tools/perf/util/synthetic-events.c
> index a0579c7d7b9e..43ad2298a933 100644
> --- a/tools/perf/util/synthetic-events.c
> +++ b/tools/perf/util/synthetic-events.c
> @@ -866,14 +866,16 @@ int perf_event__synthesize_thread_map(struct perf_tool *tool,
>
>         err = 0;
>         for (thread = 0; thread < threads->nr; ++thread) {
> +               /*
> +                * We may race with exiting thread, so don't stop just because
> +                * one thread couldn't be synthesized.
> +                */
>                 if (__event__synthesize_thread(comm_event, mmap_event,
>                                                fork_event, namespaces_event,
>                                                perf_thread_map__pid(threads, thread), 0,
>                                                process, tool, machine,
> -                                              needs_mmap, mmap_data)) {
> -                       err = -1;
> -                       break;
> -               }
> +                                              needs_mmap, mmap_data))
> +                       continue;
>
>                 /*
>                  * comm.pid is set to thread group id by
> --
> 2.39.3
>