linux-kernel - Re: [PATCH v2 3/4] drm/msm: Fix debugfs deadlock

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Date:   Thu, 1 Apr 2021 08:34:50 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jordan Crouse <jordan@...micpenguin.net>,
        "Kristian H. Kristensen" <hoegsberg@...gle.com>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <linux-arm-msm@...r.kernel.org>,
        "open list:DRM DRIVER FOR MSM ADRENO GPU" 
        <freedreno@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] drm/msm: Fix debugfs deadlock

Hi,

On Wed, Mar 31, 2021 at 6:24 PM Rob Clark <robdclark@...il.com> wrote:
>
> From: Rob Clark <robdclark@...omium.org>
>
> In normal cases the gem obj lock is acquired first before mm_lock.  The
> exception is iterating the various object lists.  In the shrinker path,
> deadlock is avoided by using msm_gem_trylock() and skipping over objects
> that cannot be locked.  But for debugfs the straightforward thing is to
> split things out into a separate list of all objects protected by it's
> own lock.
>
> Fixes: d984457b31c4 ("drm/msm: Add priv->mm_lock to protect active/inactive lists")
> Signed-off-by: Rob Clark <robdclark@...omium.org>
> Tested-by: Douglas Anderson <dianders@...omium.org>

Reviewed-by: Douglas Anderson <dianders@...omium.org>