[PATCH 3/3] drm/ttm: remove ttm_bo_wait_unreserved

Koenig, Christian Christian.Koenig at amd.com
Tue Aug 20 15:45:44 UTC 2019


Am 20.08.19 um 17:41 schrieb Daniel Vetter:
> On Tue, Aug 20, 2019 at 5:34 PM Koenig, Christian
> <Christian.Koenig at amd.com> wrote:
>> Am 20.08.19 um 17:21 schrieb Daniel Vetter:
>>> On Tue, Aug 20, 2019 at 5:16 PM Koenig, Christian
>>> <Christian.Koenig at amd.com> wrote:
>>>> Am 20.08.19 um 16:53 schrieb Daniel Vetter:
>>>>> With nouveau fixed all ttm-using drives have the correct nesting of
>>>>> mmap_sem vs dma_resv, and we can just lock the buffer.
>>>>>
>>>>> Assuming I didn't screw up anything with my audit of course.
>>>>>
>>>>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>>>>> Cc: Christian Koenig <christian.koenig at amd.com>
>>>>> Cc: Huang Rui <ray.huang at amd.com>
>>>>> Cc: Gerd Hoffmann <kraxel at redhat.com>
>>>>> Cc: "VMware Graphics" <linux-graphics-maintainer at vmware.com>
>>>>> Cc: Thomas Hellstrom <thellstrom at vmware.com>
>>>> Yes, please. But one more point: you can now remove bo->wu_mutex as well!
>>> Ah right totally forgot about that in my enthusiasm after all the
>>> auditing and fixing nouveau.
>>>
>>>> Apart from that Reviewed-by: Christian K├Ânig <christian.koenig at amd.com>
>>> Thanks, I already respun the patches, so will be in the next version.
>>> Can you pls also give this a spin on the amdgpu CI, just to make sure
>>> it's all fine? With full lockdep ofc. And then reply with a t-b.
>> I can ask for this on our call tomorrow, but I fear our CI
>> infrastructure is not ready yet.
> I thought you have some internal branch you all commit amdgpu stuff
> for, and then Alex goes and collects the pieces that are ready?

No, that part is correct. The problem is that this branch is not QA 
tested regularly as far as I know.

> Or does that all blow up if you push a patch which touches code outside
> of the dkms?

No, but the problem is related to that.

See the release branches for dkms are separate and indeed QA tested 
regularly.

But changes from amd-staging-drm-next are only cherry picked into those 
in certain intervals.

Well going to discuss that tomorrow,
Christian.

> -Daniel
>
>> Christian.
>>
>>> Thanks, Daniel
>>>>> ---
>>>>>     drivers/gpu/drm/ttm/ttm_bo.c    | 34 ---------------------------------
>>>>>     drivers/gpu/drm/ttm/ttm_bo_vm.c | 26 +------------------------
>>>>>     include/drm/ttm/ttm_bo_api.h    |  1 -
>>>>>     3 files changed, 1 insertion(+), 60 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>>>>> index 20ff56f27aa4..a952dd624b06 100644
>>>>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>>>>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>>>>> @@ -1954,37 +1954,3 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
>>>>>                 ;
>>>>>     }
>>>>>     EXPORT_SYMBOL(ttm_bo_swapout_all);
>>>>> -
>>>>> -/**
>>>>> - * ttm_bo_wait_unreserved - interruptible wait for a buffer object to become
>>>>> - * unreserved
>>>>> - *
>>>>> - * @bo: Pointer to buffer
>>>>> - */
>>>>> -int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo)
>>>>> -{
>>>>> -     int ret;
>>>>> -
>>>>> -     /*
>>>>> -      * In the absense of a wait_unlocked API,
>>>>> -      * Use the bo::wu_mutex to avoid triggering livelocks due to
>>>>> -      * concurrent use of this function. Note that this use of
>>>>> -      * bo::wu_mutex can go away if we change locking order to
>>>>> -      * mmap_sem -> bo::reserve.
>>>>> -      */
>>>>> -     ret = mutex_lock_interruptible(&bo->wu_mutex);
>>>>> -     if (unlikely(ret != 0))
>>>>> -             return -ERESTARTSYS;
>>>>> -     if (!dma_resv_is_locked(bo->base.resv))
>>>>> -             goto out_unlock;
>>>>> -     ret = dma_resv_lock_interruptible(bo->base.resv, NULL);
>>>>> -     if (ret == -EINTR)
>>>>> -             ret = -ERESTARTSYS;
>>>>> -     if (unlikely(ret != 0))
>>>>> -             goto out_unlock;
>>>>> -     dma_resv_unlock(bo->base.resv);
>>>>> -
>>>>> -out_unlock:
>>>>> -     mutex_unlock(&bo->wu_mutex);
>>>>> -     return ret;
>>>>> -}
>>>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>>>> index 76eedb963693..505e1787aeea 100644
>>>>> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>>>> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
>>>>> @@ -125,31 +125,7 @@ static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
>>>>>                 &bdev->man[bo->mem.mem_type];
>>>>>         struct vm_area_struct cvma;
>>>>>
>>>>> -     /*
>>>>> -      * Work around locking order reversal in fault / nopfn
>>>>> -      * between mmap_sem and bo_reserve: Perform a trylock operation
>>>>> -      * for reserve, and if it fails, retry the fault after waiting
>>>>> -      * for the buffer to become unreserved.
>>>>> -      */
>>>>> -     if (unlikely(!dma_resv_trylock(bo->base.resv))) {
>>>>> -             if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
>>>>> -                     if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
>>>>> -                             ttm_bo_get(bo);
>>>>> -                             up_read(&vmf->vma->vm_mm->mmap_sem);
>>>>> -                             (void) ttm_bo_wait_unreserved(bo);
>>>>> -                             ttm_bo_put(bo);
>>>>> -                     }
>>>>> -
>>>>> -                     return VM_FAULT_RETRY;
>>>>> -             }
>>>>> -
>>>>> -             /*
>>>>> -              * If we'd want to change locking order to
>>>>> -              * mmap_sem -> bo::reserve, we'd use a blocking reserve here
>>>>> -              * instead of retrying the fault...
>>>>> -              */
>>>>> -             return VM_FAULT_NOPAGE;
>>>>> -     }
>>>>> +     dma_resv_lock(bo->base.resv, NULL);
>>>>>
>>>>>         /*
>>>>>          * Refuse to fault imported pages. This should be handled
>>>>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>>>>> index 43c4929a2171..6b50e624e3e2 100644
>>>>> --- a/include/drm/ttm/ttm_bo_api.h
>>>>> +++ b/include/drm/ttm/ttm_bo_api.h
>>>>> @@ -765,7 +765,6 @@ ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
>>>>>     int ttm_bo_swapout(struct ttm_bo_global *glob,
>>>>>                         struct ttm_operation_ctx *ctx);
>>>>>     void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
>>>>> -int ttm_bo_wait_unreserved(struct ttm_buffer_object *bo);
>>>>>
>>>>>     /**
>>>>>      * ttm_bo_uses_embedded_gem_object - check if the given bo uses the
>



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