linux-kernel - Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver configuration to kernel

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Date:   Tue, 3 Jul 2018 11:47:00 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>, ast@...nel.org,
        Greg KH <gregkh@...uxfoundation.org>,
        "H. Peter Anvin" <hpa@...or.com>, linux-s390@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver
 configuration to kernel

On Tue, 3 Jul 2018 at 07:40, Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Mon, Jul 02, 2018 at 04:33:29PM -0600, Mathieu Poirier wrote:
>
> SNIP
>
> > +static int
> > +perf_event_process_drv_config(struct perf_event *event, char *config_str)
> > +{
> > +     int ret = -EINVAL;
> > +     void *drv_data;
> > +
> > +     /* Make sure ctx.mutex it held */
> > +     lockdep_assert_held(&event->ctx->mutex);
> > +
> > +     /* Children take their configuration from their parent */
> > +     if (WARN_ON_ONCE(event->parent))
> > +             goto out;
> > +
> > +     drv_data = event->pmu->drv_config_validate(event, config_str);
> > +     if (!drv_data)
> > +             goto out;
>
> what's this check for? doc does not mention that,
> also the coresight callback does not return NULL
>

Very true - thanks for pointing this out.

Mathieu

> jirka