On Mon, Nov 04, 2019 at 06:38:01PM +0100, Daniel Vetter wrote:
> 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.
>
> v2:
> - Dont forget wu_mutex (Christian König)
> - Keep the mmap_sem-less wait optimization (Thomas)
> - Use _lock_interruptible to be good citizens (Thomas)
>
> v3: Rebase over fault handler helperification.
>
> Reviewed-by: Christian König <christian.koenig@xxxxxxx> (v2)
> Reviewed-by: Thomas Hellström <thellstrom@xxxxxxxxxx> (v2)
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> Cc: Christian Koenig <christian.koenig@xxxxxxx>
> Cc: Huang Rui <ray.huang@xxxxxxx>
> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> Cc: "VMware Graphics" <linux-graphics-maintainer@xxxxxxxxxx>
> Cc: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Entire series merged into drm-misc-next (probably for 5.6) with Dave's
irc-ack for the nouveau patch.
-Daniel
> ---
> drivers/gpu/drm/ttm/ttm_bo.c | 36 -------------------------------
> drivers/gpu/drm/ttm/ttm_bo_util.c | 1 -
> drivers/gpu/drm/ttm/ttm_bo_vm.c | 18 +++++-----------
> include/drm/ttm/ttm_bo_api.h | 4 ----
> 4 files changed, 5 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 8d91b0428af1..5df596fb0280 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -161,7 +161,6 @@ static void ttm_bo_release_list(struct kref *list_kref)
> dma_fence_put(bo->moving);
> if (!ttm_bo_uses_embedded_gem_object(bo))
> dma_resv_fini(&bo->base._resv);
> - mutex_destroy(&bo->wu_mutex);
> bo->destroy(bo);
> ttm_mem_global_free(&ttm_mem_glob, acc_size);
> }
> @@ -1299,7 +1298,6 @@ int ttm_bo_init_reserved(struct ttm_bo_device *bdev,
> INIT_LIST_HEAD(&bo->ddestroy);
> INIT_LIST_HEAD(&bo->swap);
> INIT_LIST_HEAD(&bo->io_reserve_lru);
> - mutex_init(&bo->wu_mutex);
> bo->bdev = bdev;
> bo->type = type;
> bo->num_pages = num_pages;
> @@ -1903,37 +1901,3 @@ void ttm_bo_swapout_all(struct ttm_bo_device *bdev)
> while (ttm_bo_swapout(&ttm_bo_glob, &ctx) == 0);
> }
> 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_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
> index 6b0883a1776e..2b0e5a088da0 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_util.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
> @@ -504,7 +504,6 @@ static int ttm_buffer_object_transfer(struct ttm_buffer_object *bo,
> INIT_LIST_HEAD(&fbo->base.lru);
> INIT_LIST_HEAD(&fbo->base.swap);
> INIT_LIST_HEAD(&fbo->base.io_reserve_lru);
> - mutex_init(&fbo->base.wu_mutex);
> fbo->base.moving = NULL;
> drm_vma_node_reset(&fbo->base.base.vma_node);
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> index 11863fbdd5d6..91466cfb6f16 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
> @@ -128,30 +128,22 @@ static unsigned long ttm_bo_io_mem_pfn(struct ttm_buffer_object *bo,
> vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
> struct vm_fault *vmf)
> {
> - /*
> - * 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);
> + if (!dma_resv_lock_interruptible(bo->base.resv,
> + NULL))
> + dma_resv_unlock(bo->base.resv);
> 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;
> + if (dma_resv_lock_interruptible(bo->base.resv, NULL))
> + return VM_FAULT_NOPAGE;
> }
>
> return 0;
> diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
> index 65e399d280f7..e8b0f0c66059 100644
> --- a/include/drm/ttm/ttm_bo_api.h
> +++ b/include/drm/ttm/ttm_bo_api.h
> @@ -154,7 +154,6 @@ struct ttm_tt;
> * @offset: The current GPU offset, which can have different meanings
> * depending on the memory type. For SYSTEM type memory, it should be 0.
> * @cur_placement: Hint of current placement.
> - * @wu_mutex: Wait unreserved mutex.
> *
> * Base class for TTM buffer object, that deals with data placement and CPU
> * mappings. GPU mappings are really up to the driver, but for simpler GPUs
> @@ -222,8 +221,6 @@ struct ttm_buffer_object {
> uint64_t offset; /* GPU address space is independent of CPU word size */
>
> struct sg_table *sg;
> -
> - struct mutex wu_mutex;
> };
>
> /**
> @@ -707,7 +704,6 @@ 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
> --
> 2.24.0.rc2
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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