On 15.02.2017 04:16, zhoucm1 wrote:
> On 2017å¹´02æ??14æ?¥ 18:37, Nicolai Hähnle wrote:
>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>
>> Allow callers to opt out of calling ttm_bo_validate immediately. This
>> allows more flexibility in how locking of the reservation object is
>> done, which is needed to fix a locking bug (destroy locked mutex)
>> in amdgpu.
>>
>> Signed-off-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
>> ---
>> drivers/gpu/drm/ttm/ttm_bo.c | 62
>> +++++++++++++++++++++++++++++---------------
>> include/drm/ttm/ttm_bo_api.h | 45 ++++++++++++++++++++++++++++++++
>> 2 files changed, 86 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>> index 76bee42..ce4c0f5 100644
>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>> @@ -1120,41 +1120,30 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
>> }
>> EXPORT_SYMBOL(ttm_bo_validate);
>> -int ttm_bo_init(struct ttm_bo_device *bdev,
>> - struct ttm_buffer_object *bo,
>> - unsigned long size,
>> - enum ttm_bo_type type,
>> - struct ttm_placement *placement,
>> - uint32_t page_alignment,
>> - bool interruptible,
>> - struct file *persistent_swap_storage,
>> - size_t acc_size,
>> - struct sg_table *sg,
>> - struct reservation_object *resv,
>> - void (*destroy) (struct ttm_buffer_object *))
>> +int ttm_bo_init_top(struct ttm_bo_device *bdev,
>> + struct ttm_buffer_object *bo,
>> + unsigned long size,
>> + enum ttm_bo_type type,
>> + uint32_t page_alignment,
>> + struct file *persistent_swap_storage,
>> + size_t acc_size,
>> + struct sg_table *sg,
>> + struct reservation_object *resv,
>> + void (*destroy) (struct ttm_buffer_object *))
>> {
>> int ret = 0;
>> unsigned long num_pages;
>> struct ttm_mem_global *mem_glob = bdev->glob->mem_glob;
>> - bool locked;
>> ret = ttm_mem_global_alloc(mem_glob, acc_size, false, false);
>> if (ret) {
>> pr_err("Out of kernel memory\n");
>> - if (destroy)
>> - (*destroy)(bo);
>> - else
>> - kfree(bo);
>> return -ENOMEM;
>> }
>> num_pages = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>> if (num_pages == 0) {
>> pr_err("Illegal buffer object size\n");
>> - if (destroy)
>> - (*destroy)(bo);
>> - else
>> - kfree(bo);
>> ttm_mem_global_free(mem_glob, acc_size);
>> return -EINVAL;
>> }
>> @@ -1204,6 +1193,37 @@ int ttm_bo_init(struct ttm_bo_device *bdev,
>> ret = drm_vma_offset_add(&bdev->vma_manager, &bo->vma_node,
>> bo->mem.num_pages);
> if (ret && !resv), we should call
> reservation_object_fini(&bo->ttm_resv), right?
Good point, though actually, ret can never be != 0 here, so this can be
simplified a bit.
>> + return ret;
>> +}
>> +EXPORT_SYMBOL(ttm_bo_init_top);
>> +
>> +int ttm_bo_init(struct ttm_bo_device *bdev,
>> + struct ttm_buffer_object *bo,
>> + unsigned long size,
>> + enum ttm_bo_type type,
>> + struct ttm_placement *placement,
>> + uint32_t page_alignment,
>> + bool interruptible,
>> + struct file *persistent_swap_storage,
>> + size_t acc_size,
>> + struct sg_table *sg,
>> + struct reservation_object *resv,
>> + void (*destroy) (struct ttm_buffer_object *))
>> +{
>> + bool locked;
>> + int ret;
>> +
> Can we lock resv anyway before ttm_bo_init_top like what you did in
> patch #3? if yes, seems we don't need patch#3 any more, right?
>
>
> if (!resv) {
> bool locked;
>
> reservation_object_init(&bo->tbo.ttm_resv);
> locked = ww_mutex_trylock(&bo->tbo.ttm_resv.lock);
> WARN_ON(!locked);
> }
> r = ttm_bo_init_top(&adev->mman.bdev, &bo->tbo, size, type,
> page_align, NULL,
> acc_size, sg, resv ? resv : &bo->tbo.ttm_resv,
> &amdgpu_ttm_bo_destroy);
No, because there's still different behavior when it comes to unlocking.
There are three different behaviors that are needed:
1. resv == NULL, and leaving ttm_bo_init with the BO unreserved.
2. resv != NULL, and not changing the reserved status during initialization.
3. resv != NULL, and leaving initialization with the BO reserved, but
unlocking when the BO is destroyed.
1+2 can be expressed well with the ttm_bo_init interface, but 3 cannot.
I think a possible alternative would be to change ttm_bo_init so that it
always returns on success with the BO reserved, but that would require
changing all the drivers, and I don't really see the advantage over just
being more explicit in each driver.
Cheers,
Nicolai
>
> Regards,
> David Zhou
>> + ret = ttm_bo_init_top(bdev, bo, size, type, page_alignment,
>> + persistent_swap_storage, acc_size, sg, resv,
>> + destroy);
>> + if (ret) {
>> + if (destroy)
>> + (*destroy)(bo);
>> + else
>> + kfree(bo);
>> + return ret;
>> + }
>> +
>> /* passed reservation objects should already be locked,
>> * since otherwise lockdep will be angered in radeon.
>> */
>> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
>> index f195899..d44b8e4 100644
>> --- a/include/drm/ttm/ttm_bo_api.h
>> +++ b/include/drm/ttm/ttm_bo_api.h
>> @@ -453,6 +453,51 @@ size_t ttm_bo_dma_acc_size(struct ttm_bo_device
>> *bdev,
>> unsigned struct_size);
>> /**
>> + * ttm_bo_init_top
>> + *
>> + * @bdev: Pointer to a ttm_bo_device struct.
>> + * @bo: Pointer to a ttm_buffer_object to be initialized.
>> + * @size: Requested size of buffer object.
>> + * @type: Requested type of buffer object.
>> + * @flags: Initial placement flags.
>> + * @page_alignment: Data alignment in pages.
>> + * @persistent_swap_storage: Usually the swap storage is deleted for
>> buffers
>> + * pinned in physical memory. If this behaviour is not desired, this
>> member
>> + * holds a pointer to a persistent shmem object. Typically, this would
>> + * point to the shmem object backing a GEM object if TTM is used to
>> back a
>> + * GEM user interface.
>> + * @acc_size: Accounted size for this object.
>> + * @resv: Pointer to a reservation_object, or NULL to let ttm
>> allocate one.
>> + * @destroy: Destroy function. Use NULL for kfree().
>> + *
>> + * This function initializes a pre-allocated struct ttm_buffer_object.
>> + * As this object may be part of a larger structure, this function,
>> + * together with the @destroy function,
>> + * enables driver-specific objects derived from a ttm_buffer_object.
>> + *
>> + * Unlike ttm_bo_init, @bo is not validated, and when an error is
>> returned,
>> + * the caller is responsible for freeing @bo (but the setup performed by
>> + * ttm_bo_init_top itself is cleaned up).
>> + *
>> + * On successful return, the object kref and list_kref are set to 1.
>> + *
>> + * Returns
>> + * -ENOMEM: Out of memory.
>> + * -EINVAL: Invalid buffer size.
>> + */
>> +
>> +extern int ttm_bo_init_top(struct ttm_bo_device *bdev,
>> + struct ttm_buffer_object *bo,
>> + unsigned long size,
>> + enum ttm_bo_type type,
>> + uint32_t page_alignment,
>> + struct file *persistent_swap_storage,
>> + size_t acc_size,
>> + struct sg_table *sg,
>> + struct reservation_object *resv,
>> + void (*destroy) (struct ttm_buffer_object *));
>> +
>> +/**
>> * ttm_bo_init
>> *
>> * @bdev: Pointer to a ttm_bo_device struct.
>
