Re: [PATCH] fixup! drm/msm: Separate locking of buffer resources from struct_mutex

[Sushmita Susheelendra <ssusheel-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

Sounds good.

On 2017-06-16 15:44, Rob Clark wrote:
> On Fri, Jun 16, 2017 at 5:32 PM,  <ssusheel@codeaurora.org> wrote:
>> Hi Rob,
>> 
>> This looks good to me!
>> 
>> Just one nit: msm_gem_vunmap becomes very shrinker specific as it 
>> holds the
>> msm_obj->lock with the shrinker class. Should we have the caller i.e.
>> msm_gem_shrinker_vmap hold it instead? Or change it's name to
>> msm_gem_vunmap_shrinker or something like that...?
> 
> Hmm, I suppose I could pass the lock class in to msm_gem_vunmap() in
> case we ever want to call it elsewhere (iirc, i915 did something like
> that)
> 
> BR,
> -R
> 
>> It does make sense to make the madv/priv->inactive_list locking 
>> cleanup
>> separately.
>> 
>> Thanks,
>> Sushmita
>> 
>> 
>> 
>> On 2017-06-16 08:22, Rob Clark wrote:
>>> 
>>> ---
>>> Ok, 2nd fixup to handle vmap shrinking.
>>> 
>>>  drivers/gpu/drm/msm/msm_gem.c | 44
>>> +++++++++++++++++++++++++++++++++++--------
>>>  1 file changed, 36 insertions(+), 8 deletions(-)
>>> 
>>> diff --git a/drivers/gpu/drm/msm/msm_gem.c 
>>> b/drivers/gpu/drm/msm/msm_gem.c
>>> index f5d1f84..3190e05 100644
>>> --- a/drivers/gpu/drm/msm/msm_gem.c
>>> +++ b/drivers/gpu/drm/msm/msm_gem.c
>>> @@ -42,6 +42,9 @@ enum {
>>>         OBJ_LOCK_SHRINKER,
>>>  };
>>> 
>>> +static void msm_gem_vunmap_locked(struct drm_gem_object *obj);
>>> +
>>> +
>>>  static dma_addr_t physaddr(struct drm_gem_object *obj)
>>>  {
>>>         struct msm_gem_object *msm_obj = to_msm_bo(obj);
>>> @@ -484,6 +487,7 @@ int msm_gem_dumb_map_offset(struct drm_file 
>>> *file,
>>> struct drm_device *dev,
>>>  void *msm_gem_get_vaddr(struct drm_gem_object *obj)
>>>  {
>>>         struct msm_gem_object *msm_obj = to_msm_bo(obj);
>>> +       int ret = 0;
>>> 
>>>         mutex_lock(&msm_obj->lock);
>>> 
>>> @@ -492,22 +496,35 @@ void *msm_gem_get_vaddr(struct drm_gem_object 
>>> *obj)
>>>                 return ERR_PTR(-EBUSY);
>>>         }
>>> 
>>> +       /* increment vmap_count *before* vmap() call, so shrinker can
>>> +        * check vmap_count (is_vunmapable()) outside of 
>>> msm_obj->lock.
>>> +        * This guarantees that we won't try to msm_gem_vunmap() this
>>> +        * same object from within the vmap() call (while we already
>>> +        * hold msm_obj->lock)
>>> +        */
>>> +       msm_obj->vmap_count++;
>>> +
>>>         if (!msm_obj->vaddr) {
>>>                 struct page **pages = get_pages(obj);
>>>                 if (IS_ERR(pages)) {
>>> -                       mutex_unlock(&msm_obj->lock);
>>> -                       return ERR_CAST(pages);
>>> +                       ret = PTR_ERR(pages);
>>> +                       goto fail;
>>>                 }
>>>                 msm_obj->vaddr = vmap(pages, obj->size >> PAGE_SHIFT,
>>>                                 VM_MAP, 
>>> pgprot_writecombine(PAGE_KERNEL));
>>>                 if (msm_obj->vaddr == NULL) {
>>> -                       mutex_unlock(&msm_obj->lock);
>>> -                       return ERR_PTR(-ENOMEM);
>>> +                       ret = -ENOMEM;
>>> +                       goto fail;
>>>                 }
>>>         }
>>> -       msm_obj->vmap_count++;
>>> +
>>>         mutex_unlock(&msm_obj->lock);
>>>         return msm_obj->vaddr;
>>> +
>>> +fail:
>>> +       msm_obj->vmap_count--;
>>> +       mutex_unlock(&msm_obj->lock);
>>> +       return ERR_PTR(ret);
>>>  }
>>> 
>>>  void msm_gem_put_vaddr(struct drm_gem_object *obj)
>>> @@ -554,7 +571,7 @@ void msm_gem_purge(struct drm_gem_object *obj)
>>> 
>>>         put_iova(obj);
>>> 
>>> -       msm_gem_vunmap(obj);
>>> +       msm_gem_vunmap_locked(obj);
>>> 
>>>         put_pages(obj);
>>> 
>>> @@ -576,10 +593,12 @@ void msm_gem_purge(struct drm_gem_object *obj)
>>>         mutex_unlock(&msm_obj->lock);
>>>  }
>>> 
>>> -void msm_gem_vunmap(struct drm_gem_object *obj)
>>> +static void msm_gem_vunmap_locked(struct drm_gem_object *obj)
>>>  {
>>>         struct msm_gem_object *msm_obj = to_msm_bo(obj);
>>> 
>>> +       WARN_ON(!mutex_is_locked(&msm_obj->lock));
>>> +
>>>         if (!msm_obj->vaddr || WARN_ON(!is_vunmapable(msm_obj)))
>>>                 return;
>>> 
>>> @@ -587,6 +606,15 @@ void msm_gem_vunmap(struct drm_gem_object *obj)
>>>         msm_obj->vaddr = NULL;
>>>  }
>>> 
>>> +void msm_gem_vunmap(struct drm_gem_object *obj)
>>> +{
>>> +       struct msm_gem_object *msm_obj = to_msm_bo(obj);
>>> +
>>> +       mutex_lock_nested(&msm_obj->lock, OBJ_LOCK_SHRINKER);
>>> +       msm_gem_vunmap_locked(obj);
>>> +       mutex_unlock(&msm_obj->lock);
>>> +}
>>> +
>>>  /* must be called before _move_to_active().. */
>>>  int msm_gem_sync_object(struct drm_gem_object *obj,
>>>                 struct msm_fence_context *fctx, bool exclusive)
>>> @@ -799,7 +827,7 @@ void msm_gem_free_object(struct drm_gem_object 
>>> *obj)
>>> 
>>>                 drm_prime_gem_destroy(obj, msm_obj->sgt);
>>>         } else {
>>> -               msm_gem_vunmap(obj);
>>> +               msm_gem_vunmap_locked(obj);
>>>                 put_pages(obj);
>>>         }
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