linux-kernel - Re: [PATCH 2/3] tools/power turbostat: avoid an infinite loop of restarts

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Message-ID: <CAJvTdK=tw76+79sCAa3TbVQwDdv9EGCWVrFvFbHihtH3jNcDWw@mail.gmail.com>
Date: Tue, 25 Nov 2025 14:12:38 -0500
From: Len Brown <lenb@...nel.org>
To: David Arcari <darcari@...hat.com>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] tools/power turbostat: avoid an infinite loop of restarts

this patch introduces a limit of 10-restarts per turbostat lifetime,
down from infinity.

some turbostat invocations span multiple uses of cpu online/offline --
so this limit will not fly.

On Tue, Nov 18, 2025 at 10:58 AM David Arcari <darcari@...hat.com> wrote:
>
> There are some error cases where turbostat will attempt to reinitialize
> by calling the re_initialize() function.  The code attempts to avoid
> an infinite loop by checking the value of 'restarted' in one case, but
> not others. It should be checked in all cases of restart.  Additonally,
> the 'restarted' is reset to zero at the start of the loop which also
> needs to be removed.
>
> Signed-off-by: David Arcari <darcari@...hat.com>
> Cc: Len Brown <lenb@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> ---
>  tools/power/x86/turbostat/turbostat.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
> index 584b0f7f9067..5567b9ecd516 100644
> --- a/tools/power/x86/turbostat/turbostat.c
> +++ b/tools/power/x86/turbostat/turbostat.c
> @@ -6722,7 +6722,11 @@ void turbostat_loop()
>         set_my_sched_priority(-20);
>
>  restart:
> -       restarted++;
> +       if (restarted++ > 10) {
> +               if (!retval)
> +                       retval = -1;
> +               exit(retval);
> +       }
>
>         snapshot_proc_sysfs_files();
>         retval = for_all_cpus(get_counters, EVEN_COUNTERS);
> @@ -6730,13 +6734,9 @@ void turbostat_loop()
>         if (retval < -1) {
>                 exit(retval);
>         } else if (retval == -1) {
> -               if (restarted > 10) {
> -                       exit(retval);
> -               }
>                 re_initialize();
>                 goto restart;
>         }
> -       restarted = 0;
>         done_iters = 0;
>         gettimeofday(&tv_even, (struct timezone *)NULL);
>
> --
> 2.51.0
>
>


-- 
Len Brown, Intel Open Source Technology Center