Re: [PATCH v3 1/2] drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected

From: Rob Clark <robdclark@gmail.com>
To: Jessica Zhang <quic_jesszhan@quicinc.com>
Cc: freedreno <freedreno@lists.freedesktop.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	Sean Paul <seanpaul@chromium.org>,
	Stephen Boyd <swboyd@chromium.org>,
	quic_aravindh@quicinc.com,
	Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
	Abhinav Kumar <quic_abhinavk@quicinc.com>,
	Tomeu Vizoso <tomeu.vizoso@collabora.com>
Subject: Re: [PATCH v3 1/2] drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected
Date: Thu, 5 May 2022 15:01:45 -0700	[thread overview]
Message-ID: <CAF6AEGsFAkozD1j+padLREzGWNyzq8eVM9YxsX4=P4SROJ_0wA@mail.gmail.com> (raw)
In-Reply-To: <20220505214051.155-1-quic_jesszhan@quicinc.com>

On Thu, May 5, 2022 at 2:41 PM Jessica Zhang <quic_jesszhan@quicinc.com> wrote:
>
> mdp5_get_global_state runs the risk of hitting a -EDEADLK when acquiring
> the modeset lock, but currently mdp5_pipe_release doesn't check for if
> an error is returned. Because of this, there is a possibility of
> mdp5_pipe_release hitting a NULL dereference error.
>
> To avoid this, let's have mdp5_pipe_release check if
> mdp5_get_global_state returns an error and propogate that error.
>
> Changes since v1:
> - Separated declaration and initialization of *new_state to avoid
>   compiler warning
> - Fixed some spelling mistakes in commit message
>
> Changes since v2:
> - Return 0 in case where hwpipe is NULL as this is considered normal
>   behavior
> - Added 2nd patch in series to fix a similar NULL dereference issue in
>   mdp5_mixer_release
>
> Reported-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>

Fixes: 7907a0d77cb4 ("drm/msm/mdp5: Use the new private_obj state")
Reviewed-by: Rob Clark <robdclark@gmail.com>

> ---
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c  | 15 +++++++++++----
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h  |  2 +-
>  drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c | 20 ++++++++++++++++----
>  3 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> index ba6695963aa6..a4f5cb90f3e8 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c
> @@ -119,18 +119,23 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
>         return 0;
>  }
>
> -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
> +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
>  {
>         struct msm_drm_private *priv = s->dev->dev_private;
>         struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
>         struct mdp5_global_state *state = mdp5_get_global_state(s);
> -       struct mdp5_hw_pipe_state *new_state = &state->hwpipe;
> +       struct mdp5_hw_pipe_state *new_state;
>
>         if (!hwpipe)
> -               return;
> +               return 0;
> +
> +       if (IS_ERR(state))
> +               return PTR_ERR(state);
> +
> +       new_state = &state->hwpipe;
>
>         if (WARN_ON(!new_state->hwpipe_to_plane[hwpipe->idx]))
> -               return;
> +               return -EINVAL;
>
>         DBG("%s: release from plane %s", hwpipe->name,
>                 new_state->hwpipe_to_plane[hwpipe->idx]->name);
> @@ -141,6 +146,8 @@ void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
>         }
>
>         new_state->hwpipe_to_plane[hwpipe->idx] = NULL;
> +
> +       return 0;
>  }
>
>  void mdp5_pipe_destroy(struct mdp5_hw_pipe *hwpipe)
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> index 9b26d0761bd4..cca67938cab2 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.h
> @@ -37,7 +37,7 @@ int mdp5_pipe_assign(struct drm_atomic_state *s, struct drm_plane *plane,
>                      uint32_t caps, uint32_t blkcfg,
>                      struct mdp5_hw_pipe **hwpipe,
>                      struct mdp5_hw_pipe **r_hwpipe);
> -void mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
> +int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe);
>
>  struct mdp5_hw_pipe *mdp5_pipe_init(enum mdp5_pipe pipe,
>                 uint32_t reg_offset, uint32_t caps);
> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> index 228b22830970..979458482841 100644
> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_plane.c
> @@ -311,12 +311,24 @@ static int mdp5_plane_atomic_check_with_state(struct drm_crtc_state *crtc_state,
>                                 mdp5_state->r_hwpipe = NULL;
>
>
> -                       mdp5_pipe_release(state->state, old_hwpipe);
> -                       mdp5_pipe_release(state->state, old_right_hwpipe);
> +                       ret = mdp5_pipe_release(state->state, old_hwpipe);
> +                       if (ret)
> +                               return ret;
> +
> +                       ret = mdp5_pipe_release(state->state, old_right_hwpipe);
> +                       if (ret)
> +                               return ret;
> +
>                 }
>         } else {
> -               mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> -               mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> +               ret = mdp5_pipe_release(state->state, mdp5_state->hwpipe);
> +               if (ret)
> +                       return ret;
> +
> +               ret = mdp5_pipe_release(state->state, mdp5_state->r_hwpipe);
> +               if (ret)
> +                       return ret;
> +
>                 mdp5_state->hwpipe = mdp5_state->r_hwpipe = NULL;
>         }
>
> --
> 2.35.1
>