The only remaining use for this is to protect against setting a new exclusive fence while we grab both exclusive and shared. That can also be archived by looking if the exclusive fence has changed or not after completing the operation.
Signed-off-by: Christian König christian.koenig@amd.com --- drivers/dma-buf/dma-buf.c | 14 ++--- drivers/dma-buf/reservation.c | 58 +++++++------------ .../gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 8 +-- drivers/gpu/drm/i915/gem/i915_gem_busy.c | 11 ++-- include/linux/reservation.h | 3 - 5 files changed, 33 insertions(+), 61 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index f45bfb29ef96..c4ee4ccbfc40 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -199,7 +199,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) struct reservation_object_list *fobj; struct dma_fence *fence_excl; __poll_t events; - unsigned shared_count, seq; + unsigned shared_count;
dmabuf = file->private_data; if (!dmabuf || !dmabuf->resv) @@ -214,16 +214,16 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll) return 0;
retry: - seq = read_seqcount_begin(&resv->seq); rcu_read_lock();
+ fence_excl = rcu_dereference(resv->fence_excl); fobj = rcu_dereference(resv->fence); if (fobj) shared_count = fobj->shared_count; else shared_count = 0; - fence_excl = rcu_dereference(resv->fence_excl); - if (read_seqcount_retry(&resv->seq, seq)) { + + if (rcu_dereference(resv->fence_excl) != fence_excl) { rcu_read_unlock(); goto retry; } @@ -1157,7 +1157,6 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused) struct reservation_object *robj; struct reservation_object_list *fobj; struct dma_fence *fence; - unsigned seq; int count = 0, attach_count, shared_count, i; size_t size = 0;
@@ -1189,12 +1188,11 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
robj = buf_obj->resv; while (true) { - seq = read_seqcount_begin(&robj->seq); rcu_read_lock(); + fence = rcu_dereference(robj->fence_excl); fobj = rcu_dereference(robj->fence); shared_count = fobj ? fobj->shared_count : 0; - fence = rcu_dereference(robj->fence_excl); - if (!read_seqcount_retry(&robj->seq, seq)) + if (rcu_dereference(robj->fence_excl) != fence) break; rcu_read_unlock(); } diff --git a/drivers/dma-buf/reservation.c b/drivers/dma-buf/reservation.c index 69c826553c72..d8ed6235a3eb 100644 --- a/drivers/dma-buf/reservation.c +++ b/drivers/dma-buf/reservation.c @@ -49,12 +49,6 @@ DEFINE_WD_CLASS(reservation_ww_class); EXPORT_SYMBOL(reservation_ww_class);
-struct lock_class_key reservation_seqcount_class; -EXPORT_SYMBOL(reservation_seqcount_class); - -const char reservation_seqcount_string[] = "reservation_seqcount"; -EXPORT_SYMBOL(reservation_seqcount_string); - /** * reservation_object_init - initialize a reservation object * @obj: the reservation object @@ -62,9 +56,6 @@ EXPORT_SYMBOL(reservation_seqcount_string); void reservation_object_init(struct reservation_object *obj) { ww_mutex_init(&obj->lock, &reservation_ww_class); - - __seqcount_init(&obj->seq, reservation_seqcount_string, - &reservation_seqcount_class); RCU_INIT_POINTER(obj->fence, NULL); RCU_INIT_POINTER(obj->fence_excl, NULL); } @@ -251,12 +242,10 @@ void reservation_object_add_excl_fence(struct reservation_object *obj, dma_fence_get(fence);
preempt_disable(); - write_seqcount_begin(&obj->seq); - /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(obj->fence_excl, fence); + /* pointer update must be visible before we modify the shared_count */ if (old) - old->shared_count = 0; - write_seqcount_end(&obj->seq); + smp_store_mb(old->shared_count, 0); preempt_enable();
/* inplace update, no shared fences */ @@ -340,11 +329,8 @@ int reservation_object_copy_fences(struct reservation_object *dst, old = reservation_object_get_excl(dst);
preempt_disable(); - write_seqcount_begin(&dst->seq); - /* write_seqcount_begin provides the necessary memory barrier */ RCU_INIT_POINTER(dst->fence_excl, new); - RCU_INIT_POINTER(dst->fence, dst_list); - write_seqcount_end(&dst->seq); + rcu_assign_pointer(dst->fence, dst_list); preempt_enable();
if (src_list) @@ -380,18 +366,14 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj,
do { struct reservation_object_list *fobj; - unsigned int i, seq; + unsigned int i; size_t sz = 0;
shared_count = i = 0;
rcu_read_lock(); - seq = read_seqcount_begin(&obj->seq); - - fence_excl = rcu_dereference(obj->fence_excl); - if (fence_excl && !dma_fence_get_rcu(fence_excl)) - goto unlock;
+ fence_excl = dma_fence_get_rcu_safe(&obj->fence_excl); fobj = rcu_dereference(obj->fence); if (fobj) sz += sizeof(*shared) * fobj->shared_max; @@ -428,7 +410,8 @@ int reservation_object_get_fences_rcu(struct reservation_object *obj, } }
- if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) { + if (i != shared_count || + rcu_dereference(obj->fence_excl) != fence_excl) { while (i--) dma_fence_put(shared[i]); dma_fence_put(fence_excl); @@ -472,18 +455,17 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, bool wait_all, bool intr, unsigned long timeout) { - struct dma_fence *fence; - unsigned seq, shared_count; + struct dma_fence *fence, *fence_excl; long ret = timeout ? timeout : 1; + unsigned shared_count; int i;
retry: shared_count = 0; - seq = read_seqcount_begin(&obj->seq); rcu_read_lock(); i = -1;
- fence = rcu_dereference(obj->fence_excl); + fence = fence_excl = rcu_dereference(obj->fence_excl); if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) { if (!dma_fence_get_rcu(fence)) goto unlock_retry; @@ -524,13 +506,13 @@ long reservation_object_wait_timeout_rcu(struct reservation_object *obj, } }
+ if (rcu_dereference(obj->fence_excl) != fence_excl) { + dma_fence_put(fence); + goto unlock_retry; + } + rcu_read_unlock(); if (fence) { - if (read_seqcount_retry(&obj->seq, seq)) { - dma_fence_put(fence); - goto retry; - } - ret = dma_fence_wait_timeout(fence, intr, ret); dma_fence_put(fence); if (ret > 0 && wait_all && (i + 1 < shared_count)) @@ -575,14 +557,15 @@ reservation_object_test_signaled_single(struct dma_fence *passed_fence) bool reservation_object_test_signaled_rcu(struct reservation_object *obj, bool test_all) { - unsigned seq, shared_count; + struct dma_fence *fence_excl; + unsigned shared_count; int ret;
rcu_read_lock(); retry: + fence_excl = rcu_dereference(obj->fence_excl); ret = true; shared_count = 0; - seq = read_seqcount_begin(&obj->seq);
if (test_all) { unsigned i; @@ -603,12 +586,11 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, break; }
- if (read_seqcount_retry(&obj->seq, seq)) + if (rcu_dereference(obj->fence_excl) != fence_excl) goto retry; }
if (!shared_count) { - struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
if (fence_excl) { ret = reservation_object_test_signaled_single( @@ -616,7 +598,7 @@ bool reservation_object_test_signaled_rcu(struct reservation_object *obj, if (ret < 0) goto retry;
- if (read_seqcount_retry(&obj->seq, seq)) + if (rcu_dereference(obj->fence_excl) != fence_excl) goto retry; } } diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c index 1d3ee9c42f7e..a2a2ae592f20 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c @@ -251,12 +251,8 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo, new->shared_max = old->shared_max; new->shared_count = k;
- /* Install the new fence list, seqcount provides the barriers */ - preempt_disable(); - write_seqcount_begin(&resv->seq); - RCU_INIT_POINTER(resv->fence, new); - write_seqcount_end(&resv->seq); - preempt_enable(); + /* Install the new fence list */ + rcu_assign_pointer(resv->fence, new);
/* Drop the references to the removed fences or move them to ef_list */ for (i = j, k = 0; i < old->shared_count; ++i) { diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c b/drivers/gpu/drm/i915/gem/i915_gem_busy.c index 6ad93a09968c..6e8a6e4f39ff 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c @@ -83,7 +83,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, struct drm_i915_gem_busy *args = data; struct drm_i915_gem_object *obj; struct reservation_object_list *list; - unsigned int seq; + struct dma_fence *fence_excl; int err;
err = -ENOENT; @@ -110,11 +110,9 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, * */ retry: - 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)); + fence_excl = rcu_dereference(obj->base.resv->fence_excl); + args->busy = busy_check_writer(fence_excl);
/* Translate shared fences to READ set of engines */ list = rcu_dereference(obj->base.resv->fence); @@ -129,7 +127,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data, } }
- if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq)) + if (args->busy && + rcu_dereference(obj->base.resv->fence_excl) != fence_excl) goto retry;
err = 0; diff --git a/include/linux/reservation.h b/include/linux/reservation.h index 56b782fec49b..2b0b2a1aeae2 100644 --- a/include/linux/reservation.h +++ b/include/linux/reservation.h @@ -46,8 +46,6 @@ #include <linux/rcupdate.h>
extern struct ww_class reservation_ww_class; -extern struct lock_class_key reservation_seqcount_class; -extern const char reservation_seqcount_string[];
/** * struct reservation_object_list - a list of shared fences @@ -71,7 +69,6 @@ struct reservation_object_list { */ struct reservation_object { struct ww_mutex lock; - seqcount_t seq;
struct dma_fence __rcu *fence_excl; struct reservation_object_list __rcu *fence;