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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 23 Feb 2021 15:48:54 +0100
Message-ID: <CACT4Y+YGrj3zc+KsxQ0=N5t3dPy58FwVuy=MY95RphOD4i4FHg@mail.gmail.com>
Subject: Re: [PATCH RFC 1/4] perf/core: Apply PERF_EVENT_IOC_MODIFY_ATTRIBUTES
 to children
To:     Marco Elver <elver@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexander Potapenko <glider@google.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Arnd Bergmann <arnd@arndb.de>,
        Christian Brauner <christian@brauner.io>,
        Jann Horn <jannh@google.com>, Jens Axboe <axboe@kernel.dk>,
        Matt Morehouse <mascasa@google.com>,
        Peter Collingbourne <pcc@google.com>,
        Ian Rogers <irogers@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        linux-arch <linux-arch@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-m68k@lists.linux-m68k.org,
        "the arch/x86 maintainers" <x86@kernel.org>
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On Tue, Feb 23, 2021 at 3:34 PM Marco Elver <elver@google.com> wrote:
>
> As with other ioctls (such as PERF_EVENT_IOC_{ENABLE,DISABLE}), fix up
> handling of PERF_EVENT_IOC_MODIFY_ATTRIBUTES to also apply to children.
>
> Link: https://lkml.kernel.org/r/YBqVaY8aTMYtoUnX@hirez.programming.kicks-ass.net
> Suggested-by: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Marco Elver <elver@google.com>

Reviewed-by: Dmitry Vyukov <dvyukov@google.com>


> ---
>  kernel/events/core.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 129dee540a8b..37a8297be164 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3179,16 +3179,36 @@ static int perf_event_modify_breakpoint(struct perf_event *bp,
>  static int perf_event_modify_attr(struct perf_event *event,
>                                   struct perf_event_attr *attr)
>  {
> +       int (*func)(struct perf_event *, struct perf_event_attr *);
> +       struct perf_event *child;
> +       int err;
> +
>         if (event->attr.type != attr->type)
>                 return -EINVAL;
>
>         switch (event->attr.type) {
>         case PERF_TYPE_BREAKPOINT:
> -               return perf_event_modify_breakpoint(event, attr);
> +               func = perf_event_modify_breakpoint;
> +               break;
>         default:
>                 /* Place holder for future additions. */
>                 return -EOPNOTSUPP;
>         }
> +
> +       WARN_ON_ONCE(event->ctx->parent_ctx);
> +
> +       mutex_lock(&event->child_mutex);
> +       err = func(event, attr);
> +       if (err)
> +               goto out;
> +       list_for_each_entry(child, &event->child_list, child_list) {
> +               err = func(child, attr);
> +               if (err)
> +                       goto out;
> +       }
> +out:
> +       mutex_unlock(&event->child_mutex);
> +       return err;
>  }
>
>  static void ctx_sched_out(struct perf_event_context *ctx,
> --
> 2.30.0.617.g56c4b15f3c-goog
>