linux-kernel - Re: [PATCH v2 1/2] drm/panfrost: Handle resetting on timeout better

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Message-ID: <CAL_JsqKjvuhw_fWVyfptbgP-_Q6R44i6y+pg8FojO4BujDmxnA@mail.gmail.com>
Date:   Wed, 9 Oct 2019 13:39:55 -0500
From:   Rob Herring <robh@...nel.org>
To:     Steven Price <steven.price@....com>
Cc:     Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...ux.ie>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Neil Armstrong <narmstrong@...libre.com>
Subject: Re: [PATCH v2 1/2] drm/panfrost: Handle resetting on timeout better

On Wed, Oct 9, 2019 at 4:45 AM Steven Price <steven.price@....com> wrote:
>
> Panfrost uses multiple schedulers (one for each slot, so 2 in reality),
> and on a timeout has to stop all the schedulers to safely perform a
> reset. However more than one scheduler can trigger a timeout at the same
> time. This race condition results in jobs being freed while they are
> still in use.
>
> When stopping other slots use cancel_delayed_work_sync() to ensure that
> any timeout started for that slot has completed. Also use
> mutex_trylock() to obtain reset_lock. This means that only one thread
> attempts the reset, the other threads will simply complete without doing
> anything (the first thread will wait for this in the call to
> cancel_delayed_work_sync()).
>
> While we're here and since the function is already dependent on
> sched_job not being NULL, let's remove the unnecessary checks.
>
> Fixes: aa20236784ab ("drm/panfrost: Prevent concurrent resets")
> Tested-by: Neil Armstrong <narmstrong@...libre.com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> v2:
>  * Added fixes and tested-by tags
>  * Moved cleanup of panfrost_core_dump() comment to separate patch
>
>  drivers/gpu/drm/panfrost/panfrost_job.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)

Both patches applied.

Rob