On Wed, Jun 02, 2021 at 01:17:11PM +0200, Christian König wrote:
> When the comment needs to state explicitly that this
> doesn't get a reference to the object then the function
> is named rather badly.
>
> Rename the function and use rcu_dereference_check(), this
> way it can be used from both rcu as well as lock protected
> critical sections.
>
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
I'd call this dma_resv_exlusive_fence, since without that it's a bit close
to dma_resv_make_exclusive or something like that. But this is definitely
better than the previous pointer deref in a "I'm totally getting you a
full reference" trenchcoat thing.
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/dma-buf/dma-buf.c | 4 ++--
> drivers/dma-buf/dma-resv.c | 10 +++++-----
> drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 2 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c | 2 +-
> drivers/gpu/drm/etnaviv/etnaviv_gem.c | 2 +-
> drivers/gpu/drm/i915/gem/i915_gem_busy.c | 3 +--
> drivers/gpu/drm/msm/msm_gem.c | 4 ++--
> drivers/gpu/drm/nouveau/nouveau_bo.c | 2 +-
> drivers/gpu/drm/nouveau/nouveau_fence.c | 2 +-
> drivers/gpu/drm/radeon/radeon_display.c | 2 +-
> drivers/gpu/drm/radeon/radeon_sync.c | 2 +-
> drivers/gpu/drm/radeon/radeon_uvd.c | 2 +-
> drivers/gpu/drm/ttm/ttm_bo.c | 2 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_resource.c | 2 +-
> include/linux/dma-resv.h | 13 +++++--------
> 15 files changed, 25 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index d3b4e370dbc1..4d0ddc712f1e 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -234,7 +234,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
> shared_count = fobj->shared_count;
> else
> shared_count = 0;
> - fence_excl = rcu_dereference(resv->fence_excl);
> + fence_excl = dma_resv_exclusive(resv);
> if (read_seqcount_retry(&resv->seq, seq)) {
> rcu_read_unlock();
> goto retry;
> @@ -1385,7 +1385,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
> robj = buf_obj->resv;
> seq = read_seqcount_begin(&robj->seq);
> rcu_read_lock();
> - fence = rcu_dereference(robj->fence_excl);
> + fence = dma_resv_exclusive(robj);
> if (fence)
> seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
> fence->ops->get_driver_name(fence),
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index 6c6195315e9f..81b032b43457 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -281,7 +281,7 @@ EXPORT_SYMBOL(dma_resv_add_shared_fence);
> */
> void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
> {
> - struct dma_fence *old_fence = dma_resv_get_excl(obj);
> + struct dma_fence *old_fence = dma_resv_exclusive(obj);
> struct dma_resv_list *old;
> u32 i = 0;
>
> @@ -377,7 +377,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
> rcu_read_unlock();
>
> src_list = dma_resv_get_list(dst);
> - old = dma_resv_get_excl(dst);
> + old = dma_resv_exclusive(dst);
>
> write_seqcount_begin(&dst->seq);
> /* write_seqcount_begin provides the necessary memory barrier */
> @@ -425,7 +425,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
> rcu_read_lock();
> seq = read_seqcount_begin(&obj->seq);
>
> - fence_excl = rcu_dereference(obj->fence_excl);
> + fence_excl = dma_resv_exclusive(obj);
> if (fence_excl && !dma_fence_get_rcu(fence_excl))
> goto unlock;
>
> @@ -520,7 +520,7 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
> rcu_read_lock();
> i = -1;
>
> - fence = rcu_dereference(obj->fence_excl);
> + fence = dma_resv_exclusive(obj);
> if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
> if (!dma_fence_get_rcu(fence))
> goto unlock_retry;
> @@ -642,7 +642,7 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
> }
>
> if (!shared_count) {
> - struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
> + struct dma_fence *fence_excl = dma_resv_exclusive(obj);
>
> if (fence_excl) {
> ret = dma_resv_test_signaled_single(fence_excl);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 73c76a3e2b12..cd5146fa6fb6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -226,7 +226,7 @@ static void amdgpu_gem_object_close(struct drm_gem_object *obj,
> if (!amdgpu_vm_ready(vm))
> goto out_unlock;
>
> - fence = dma_resv_get_excl(bo->tbo.base.resv);
> + fence = dma_resv_exclusive(bo->tbo.base.resv);
> if (fence) {
> amdgpu_bo_fence(bo, fence, true);
> fence = NULL;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> index 4e558632a5d2..c84d5b843985 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> @@ -210,7 +210,7 @@ int amdgpu_sync_resv(struct amdgpu_device *adev, struct amdgpu_sync *sync,
> return -EINVAL;
>
> /* always sync to the exclusive fence */
> - f = dma_resv_get_excl(resv);
> + f = dma_resv_exclusive(resv);
> r = amdgpu_sync_fence(sync, f);
>
> flist = dma_resv_get_list(resv);
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> index db69f19ab5bc..d4f54dea8ac1 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> @@ -471,7 +471,7 @@ static void etnaviv_gem_describe(struct drm_gem_object *obj, struct seq_file *m)
> }
> }
>
> - fence = rcu_dereference(robj->fence_excl);
> + fence = dma_resv_exclusive(robj);
> if (fence)
> etnaviv_gem_describe_fence(fence, "Exclusive", m);
> rcu_read_unlock();
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> index 25235ef630c1..02312a0c3a36 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
> @@ -113,8 +113,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
> seq = raw_read_seqcount(&obj->base.resv->seq);
>
> /* Translate the exclusive fence to the READ *and* WRITE engine */
> - args->busy =
> - busy_check_writer(rcu_dereference(obj->base.resv->fence_excl));
> + args->busy = busy_check_writer(dma_resv_exclusive(obj->base.resv));
>
> /* Translate shared fences to READ set of engines */
> list = rcu_dereference(obj->base.resv->fence);
> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
> index 56df86e5f740..54c1b53426d6 100644
> --- a/drivers/gpu/drm/msm/msm_gem.c
> +++ b/drivers/gpu/drm/msm/msm_gem.c
> @@ -819,7 +819,7 @@ int msm_gem_sync_object(struct drm_gem_object *obj,
>
> fobj = dma_resv_get_list(obj->resv);
> if (!fobj || (fobj->shared_count == 0)) {
> - fence = dma_resv_get_excl(obj->resv);
> + fence = dma_resv_exclusive(obj->resv);
> /* don't need to wait on our own fences, since ring is fifo */
> if (fence && (fence->context != fctx->context)) {
> ret = dma_fence_wait(fence, true);
> @@ -1035,7 +1035,7 @@ void msm_gem_describe(struct drm_gem_object *obj, struct seq_file *m,
> }
> }
>
> - fence = rcu_dereference(robj->fence_excl);
> + fence = dma_resv_exclusive(robj);
> if (fence)
> describe_fence(fence, "Exclusive", m);
> rcu_read_unlock();
> diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
> index e688ca77483d..ac0ebcc4ebb7 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_bo.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
> @@ -955,7 +955,7 @@ nouveau_bo_vm_cleanup(struct ttm_buffer_object *bo,
> {
> struct nouveau_drm *drm = nouveau_bdev(bo->bdev);
> struct drm_device *dev = drm->dev;
> - struct dma_fence *fence = dma_resv_get_excl(bo->base.resv);
> + struct dma_fence *fence = dma_resv_exclusive(bo->base.resv);
>
> nv10_bo_put_tile_region(dev, *old_tile, fence);
> *old_tile = new_tile;
> diff --git a/drivers/gpu/drm/nouveau/nouveau_fence.c b/drivers/gpu/drm/nouveau/nouveau_fence.c
> index e5dcbf67de7e..a6cb35181aee 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_fence.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_fence.c
> @@ -356,7 +356,7 @@ nouveau_fence_sync(struct nouveau_bo *nvbo, struct nouveau_channel *chan, bool e
> }
>
> fobj = dma_resv_get_list(resv);
> - fence = dma_resv_get_excl(resv);
> + fence = dma_resv_exclusive(resv);
>
> if (fence && (!exclusive || !fobj || !fobj->shared_count)) {
> struct nouveau_channel *prev = NULL;
> diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
> index 652af7a134bd..57c910e5ae77 100644
> --- a/drivers/gpu/drm/radeon/radeon_display.c
> +++ b/drivers/gpu/drm/radeon/radeon_display.c
> @@ -533,7 +533,7 @@ static int radeon_crtc_page_flip_target(struct drm_crtc *crtc,
> DRM_ERROR("failed to pin new rbo buffer before flip\n");
> goto cleanup;
> }
> - work->fence = dma_fence_get(dma_resv_get_excl(new_rbo->tbo.base.resv));
> + work->fence = dma_fence_get(dma_resv_exclusive(new_rbo->tbo.base.resv));
> radeon_bo_get_tiling_flags(new_rbo, &tiling_flags, NULL);
> radeon_bo_unreserve(new_rbo);
>
> diff --git a/drivers/gpu/drm/radeon/radeon_sync.c b/drivers/gpu/drm/radeon/radeon_sync.c
> index 5d3302945076..e476f90ef1c1 100644
> --- a/drivers/gpu/drm/radeon/radeon_sync.c
> +++ b/drivers/gpu/drm/radeon/radeon_sync.c
> @@ -98,7 +98,7 @@ int radeon_sync_resv(struct radeon_device *rdev,
> int r = 0;
>
> /* always sync to the exclusive fence */
> - f = dma_resv_get_excl(resv);
> + f = dma_resv_exclusive(resv);
> fence = f ? to_radeon_fence(f) : NULL;
> if (fence && fence->rdev == rdev)
> radeon_sync_fence(sync, fence);
> diff --git a/drivers/gpu/drm/radeon/radeon_uvd.c b/drivers/gpu/drm/radeon/radeon_uvd.c
> index dfa9fdbe98da..02d4bbdc9111 100644
> --- a/drivers/gpu/drm/radeon/radeon_uvd.c
> +++ b/drivers/gpu/drm/radeon/radeon_uvd.c
> @@ -477,7 +477,7 @@ static int radeon_uvd_cs_msg(struct radeon_cs_parser *p, struct radeon_bo *bo,
> return -EINVAL;
> }
>
> - f = dma_resv_get_excl(bo->tbo.base.resv);
> + f = dma_resv_exclusive(bo->tbo.base.resv);
> if (f) {
> r = radeon_fence_wait((struct radeon_fence *)f, false);
> if (r) {
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 5a7ab4b35b2d..92361556bf0b 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -262,7 +262,7 @@ static void ttm_bo_flush_all_fences(struct ttm_buffer_object *bo)
>
> rcu_read_lock();
> fobj = rcu_dereference(resv->fence);
> - fence = rcu_dereference(resv->fence_excl);
> + fence = dma_resv_exclusive(resv);
> if (fence && !fence->ops->signaled)
> dma_fence_enable_sw_signaling(fence);
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> index 62ea920addc3..c78f38ee1c20 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> @@ -1166,7 +1166,7 @@ int vmw_resources_clean(struct vmw_buffer_object *vbo, pgoff_t start,
> if (bo->moving)
> dma_fence_put(bo->moving);
> bo->moving = dma_fence_get
> - (dma_resv_get_excl(bo->base.resv));
> + (dma_resv_exclusive(bo->base.resv));
> }
>
> return 0;
> diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
> index f32a3d176513..7549ec5eb35c 100644
> --- a/include/linux/dma-resv.h
> +++ b/include/linux/dma-resv.h
> @@ -226,22 +226,19 @@ static inline void dma_resv_unlock(struct dma_resv *obj)
> }
>
> /**
> - * dma_resv_get_excl - get the reservation object's
> - * exclusive fence, with update-side lock held
> + * dma_resv_exclusive - return the object's exclusive fence
> * @obj: the reservation object
> *
> - * Returns the exclusive fence (if any). Does NOT take a
> - * reference. Writers must hold obj->lock, readers may only
> - * hold a RCU read side lock.
> + * Returns the exclusive fence (if any). Caller must either hold the objects
> + * lock or the rcu read side lock.
> *
> * RETURNS
> * The exclusive fence or NULL
> */
> static inline struct dma_fence *
> -dma_resv_get_excl(struct dma_resv *obj)
> +dma_resv_exclusive(struct dma_resv *obj)
> {
> - return rcu_dereference_protected(obj->fence_excl,
> - dma_resv_held(obj));
> + return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj));
> }
>
> /**
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
