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From: Peter Zijlstra <peterz@infradead.org>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Will Deacon <will@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Matt Morehouse <mascasa@google.com>
Subject: Re: Process-wide watchpoints
Date: Wed, 3 Feb 2021 13:22:01 +0100
Message-ID: <YBqVaY8aTMYtoUnX@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CACT4Y+bW1gpv8bz0vswaVUt-OB07oJ3NBeTi+vchAe8TTWK+mg@mail.gmail.com>

On Sun, Jan 31, 2021 at 11:04:43AM +0100, Dmitry Vyukov wrote:

> PERF_EVENT_IOC_{ENABLE,DISABLE} work as advertised.
> However, PERF_EVENT_IOC_MODIFY_ATTRIBUTES does not work for inherited
> child events.
> Does something like this make any sense to you? Are you willing to
> accept such change?
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 55d18791a72d..f6974807a32c 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -3174,7 +3174,7 @@ int perf_event_refresh(struct perf_event *event,
> int refresh)
>  }
>  EXPORT_SYMBOL_GPL(perf_event_refresh);
> 
> -static int perf_event_modify_breakpoint(struct perf_event *bp,
> +static int _perf_event_modify_breakpoint(struct perf_event *bp,
>                                          struct perf_event_attr *attr)
>  {
>         int err;
> @@ -3189,6 +3189,28 @@ static int perf_event_modify_breakpoint(struct
> perf_event *bp,
>         return err;
>  }
> 
> +static int perf_event_modify_breakpoint(struct perf_event *bp,
> +                                       struct perf_event_attr *attr)
> +{
> +       struct perf_event *child;
> +       int err;
> +
> +       WARN_ON_ONCE(bp->ctx->parent_ctx);
> +
> +       mutex_lock(&bp->child_mutex);
> +       err = _perf_event_modify_breakpoint(bp, attr);
> +       if (err)
> +               goto unlock;
> +       list_for_each_entry(child, &bp->child_list, child_list) {
> +               err = _perf_event_modify_breakpoint(child, attr);
> +               if (err)
> +                       goto unlock;
> +       }
> +unlock:
> +       mutex_unlock(&bp->child_mutex);
> +       return err;
> +}
> +
>  static int perf_event_modify_attr(struct perf_event *event,
>                                   struct perf_event_attr *attr)

Oh.. yeah, normal ioctl()s go through the perf_event_for_each_child()
thing, but that doesn't work here.

So yeah, I suppose your patch makes sense.

      parent reply index

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-12  7:46 Dmitry Vyukov
2020-11-12 10:31 ` Peter Zijlstra
2020-11-12 10:43   ` Dmitry Vyukov
     [not found]     ` <CACT4Y+bW1gpv8bz0vswaVUt-OB07oJ3NBeTi+vchAe8TTWK+mg@mail.gmail.com>
     [not found]       ` <CACT4Y+ZsKXfAxrzJGQc5mJ+QiP5sAw7zKWtciS+07qZzSf33mw@mail.gmail.com>
2021-02-01  8:50         ` Dmitry Vyukov
2021-02-03 12:29           ` Peter Zijlstra
2021-02-03 12:49             ` Dmitry Vyukov
2021-02-03 12:50               ` Dmitry Vyukov
2021-02-03 13:37               ` Peter Zijlstra
2021-02-04  8:10                 ` Dmitry Vyukov
2021-02-04  9:38                   ` Peter Zijlstra
2021-02-04  9:54                     ` Dmitry Vyukov
2021-02-04 12:09                       ` Peter Zijlstra
2021-02-04 12:53                         ` Dmitry Vyukov
2021-02-04 13:10                           ` Peter Zijlstra
2021-02-04 13:35                             ` Dmitry Vyukov
2021-02-04 13:45                               ` Peter Zijlstra
2021-02-04 14:59                               ` Peter Zijlstra
2021-02-04 13:33                           ` Peter Zijlstra
2021-02-04 13:37                             ` Dmitry Vyukov
2021-02-04 13:06                         ` Peter Zijlstra
2021-02-03  5:38         ` Namhyung Kim
2021-02-04  8:10           ` Dmitry Vyukov
2021-02-03 12:22       ` Peter Zijlstra [this message]

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