[Freedreno] [PATCH v2] drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected

[Jessica Zhang]

On 5/5/2022 1:48 AM, Dmitry Baryshkov wrote:
> On Thu, 5 May 2022 at 05:06, Rob Clark <robdclark at gmail.com> wrote:
>>
>> On Wed, May 4, 2022 at 6:55 PM Jessica Zhang <quic_jesszhan at 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
>>>
>>
>> Note that mdp5_mixer_release() needs the same treatment.. one more comment below

Got it, will submit a fix for that.

>>
>>> Signed-off-by: Jessica Zhang <quic_jesszhan at quicinc.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..97887a2be082 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 -EINVAL;
>>
>> At least per the current code, !hwpipe is "normal".. I think that fits
>> the model of things like kfree(NULL), so lets make this just return 0
> 
> Especially since we release the r_hwpipe w/o additional check. And
> r_hwpipe frequently is NULL.

Noted.

Thanks,
Jessica Zhang

> 
>>
>>> +
>>> +       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
>>>
> 
> 
> 
> -- 
> With best wishes
> Dmitry