Re: [PATCH v3 3/3] drm/amdgpu: simplify reservation handling during buffer creation

[zhoucm1 <david1.zhou@xxxxxxx>]

On 2017年02月16日 20:08, Christian König wrote:
> Am 16.02.2017 um 12:39 schrieb Nicolai Hähnle:
> > From: Nicolai Hähnle <nicolai.haehnle@xxxxxxx>
> >
> > By using ttm_bo_init_reserved instead of the manual initialization of
> > the reservation object, the reservation lock will be properly unlocked
> > and destroyed when the TTM BO initialization fails.
> >
> > Actual deadlocks caused by the missing unlock should have been fixed
> > by "drm/ttm: never add BO that failed to validate to the LRU list",
> > superseding the flawed fix in commit 38fc4856ad98 ("drm/amdgpu: fix
> > a potential deadlock in amdgpu_bo_create_restricted()").
> >
> > This change fixes remaining recursive locking errors that can be seen
> > with lock debugging enabled, and avoids the error of freeing a locked
> > mutex.
> >
> > As an additional minor bonus, buffers created with resv == NULL and
> > the AMDGPU_GEM_CREATE_VRAM_CLEARED flag are now only added to the
> > global LRU list after the fill commands have been issued.
> >
> > Fixes: 12a852219583 ("drm/amdgpu: improve 
> > AMDGPU_GEM_CREATE_VRAM_CLEARED handling (v2)")
> > Signed-off-by: Nicolai Hähnle <nicolai.haehnle@xxxxxxx>
Reviewed-by: Chunming Zhou <david1.zhou@xxxxxxx> as well

> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 17 ++++-------------
> >   1 file changed, 4 insertions(+), 13 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c 
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> > index c2e57f7..4d0536d 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
> > @@ -395,19 +395,10 @@ int amdgpu_bo_create_restricted(struct 
> > amdgpu_device *adev,
> >       amdgpu_fill_placement_to_bo(bo, placement);
> >       /* Kernel allocation are uninterruptible */
> >   -    if (!resv) {
> > -        bool locked;
> > -
> > -        reservation_object_init(&bo->tbo.ttm_resv);
> > -        locked = ww_mutex_trylock(&bo->tbo.ttm_resv.lock);
> > -        WARN_ON(!locked);
> > -    }
> > -
> >       initial_bytes_moved = atomic64_read(&adev->num_bytes_moved);
> > -    r = ttm_bo_init(&adev->mman.bdev, &bo->tbo, size, type,
> > -            &bo->placement, page_align, !kernel, NULL,
> > -            acc_size, sg, resv ? resv : &bo->tbo.ttm_resv,
> > -            &amdgpu_ttm_bo_destroy);
> > +    r = ttm_bo_init_reserved(&adev->mman.bdev, &bo->tbo, size, type,
> > +                 &bo->placement, page_align, !kernel, NULL,
> > +                 acc_size, sg, resv, &amdgpu_ttm_bo_destroy);
> >       amdgpu_cs_report_moved_bytes(adev,
> >           atomic64_read(&adev->num_bytes_moved) - initial_bytes_moved);
> >   @@ -433,7 +424,7 @@ int amdgpu_bo_create_restricted(struct 
> > amdgpu_device *adev,
> >           fence_put(fence);
> >       }
> >       if (!resv)
> > -        ww_mutex_unlock(&bo->tbo.resv->lock);
> > +        ttm_bo_unreserve(&bo->tbo);
>
> You can just use amdgpu_bo_unreserve() here. With that fixed the whole 
> set is Reviewed-by: Christian König <christian.koenig@xxxxxxx>.
>
> Regards,
> Christian.
>
> >       *bo_ptr = bo;
> >         trace_amdgpu_bo_create(bo);
>
>
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