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

From: Mathieu Poirier <mathieu.poirier@linaro.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Namhyung Kim <namhyung@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	ast@kernel.org, Greg KH <gregkh@linuxfoundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-s390@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 5/6] perf/core: Use ioctl to communicate driver configuration to kernel
Date: Tue, 3 Jul 2018 11:47:00 -0600	[thread overview]
Message-ID: <CANLsYkyAcJ3yPmdtRWnktOTLcirzxz0G2kwRjwtfhYvorXOs0Q@mail.gmail.com> (raw)
In-Reply-To: <20180703134026.GA3728@krava>

On Tue, 3 Jul 2018 at 07:40, Jiri Olsa <jolsa@redhat.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