reservation: add suppport for read-only access using rcu
This adds some extra functions to deal with rcu. reservation_object_get_fences_rcu() will obtain the list of shared and exclusive fences without obtaining the ww_mutex. reservation_object_wait_timeout_rcu() will wait on all fences of the reservation_object, without obtaining the ww_mutex. reservation_object_test_signaled_rcu() will test if all fences of the reservation_object are signaled without using the ww_mutex. reservation_object_get_excl and reservation_object_get_list require the reservation object to be held, updating requires write_seqcount_begin/end. If only the exclusive fence is needed, rcu_dereference followed by fence_get_rcu can be used, if the shared fences are needed it's recommended to use the supplied functions. Signed-off-by: Maarten Lankhorst <maarten.lankhorst@canonical.com> Acked-by: Sumit Semwal <sumit.semwal@linaro.org> Acked-by: Daniel Vetter <daniel@ffwll.ch> Reviewed-By: Thomas Hellstrom <thellstrom@vmware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Maarten Lankhorst
Greg Kroah-Hartman
parent
04a5faa8cb
commit
3c3b177a93
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@ -137,7 +137,7 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
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struct reservation_object_list *fobj;
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struct fence *fence_excl;
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unsigned long events;
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unsigned shared_count;
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unsigned shared_count, seq;
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dmabuf = file->private_data;
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if (!dmabuf || !dmabuf->resv)
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@ -151,14 +151,20 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
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if (!events)
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return 0;
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ww_mutex_lock(&resv->lock, NULL);
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retry:
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seq = read_seqcount_begin(&resv->seq);
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rcu_read_lock();
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fobj = resv->fence;
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if (!fobj)
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goto out;
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shared_count = fobj->shared_count;
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fence_excl = resv->fence_excl;
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fobj = rcu_dereference(resv->fence);
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if (fobj)
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shared_count = fobj->shared_count;
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else
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shared_count = 0;
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fence_excl = rcu_dereference(resv->fence_excl);
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if (read_seqcount_retry(&resv->seq, seq)) {
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rcu_read_unlock();
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goto retry;
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}
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if (fence_excl && (!(events & POLLOUT) || shared_count == 0)) {
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struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
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@ -176,14 +182,20 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
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spin_unlock_irq(&dmabuf->poll.lock);
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if (events & pevents) {
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if (!fence_add_callback(fence_excl, &dcb->cb,
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if (!fence_get_rcu(fence_excl)) {
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/* force a recheck */
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events &= ~pevents;
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dma_buf_poll_cb(NULL, &dcb->cb);
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} else if (!fence_add_callback(fence_excl, &dcb->cb,
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dma_buf_poll_cb)) {
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events &= ~pevents;
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fence_put(fence_excl);
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} else {
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/*
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* No callback queued, wake up any additional
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* waiters.
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*/
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fence_put(fence_excl);
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dma_buf_poll_cb(NULL, &dcb->cb);
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}
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}
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@ -205,13 +217,26 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
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goto out;
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for (i = 0; i < shared_count; ++i) {
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struct fence *fence = fobj->shared[i];
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struct fence *fence = rcu_dereference(fobj->shared[i]);
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if (!fence_get_rcu(fence)) {
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/*
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* fence refcount dropped to zero, this means
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* that fobj has been freed
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*
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* call dma_buf_poll_cb and force a recheck!
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*/
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events &= ~POLLOUT;
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dma_buf_poll_cb(NULL, &dcb->cb);
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break;
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}
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if (!fence_add_callback(fence, &dcb->cb,
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dma_buf_poll_cb)) {
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fence_put(fence);
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events &= ~POLLOUT;
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break;
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}
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fence_put(fence);
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}
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/* No callback queued, wake up any additional waiters. */
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@ -220,7 +245,7 @@ static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
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}
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out:
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ww_mutex_unlock(&resv->lock);
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rcu_read_unlock();
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return events;
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}
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@ -184,7 +184,7 @@ EXPORT_SYMBOL(fence_release);
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void fence_free(struct fence *fence)
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{
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kfree(fence);
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kfree_rcu(fence, rcu);
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}
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EXPORT_SYMBOL(fence_free);
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@ -38,6 +38,11 @@
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DEFINE_WW_CLASS(reservation_ww_class);
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EXPORT_SYMBOL(reservation_ww_class);
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struct lock_class_key reservation_seqcount_class;
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EXPORT_SYMBOL(reservation_seqcount_class);
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const char reservation_seqcount_string[] = "reservation_seqcount";
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EXPORT_SYMBOL(reservation_seqcount_string);
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/*
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* Reserve space to add a shared fence to a reservation_object,
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* must be called with obj->lock held.
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@ -82,27 +87,37 @@ reservation_object_add_shared_inplace(struct reservation_object *obj,
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{
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u32 i;
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fence_get(fence);
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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for (i = 0; i < fobj->shared_count; ++i) {
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if (fobj->shared[i]->context == fence->context) {
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struct fence *old_fence = fobj->shared[i];
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struct fence *old_fence;
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fence_get(fence);
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old_fence = rcu_dereference_protected(fobj->shared[i],
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reservation_object_held(obj));
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fobj->shared[i] = fence;
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if (old_fence->context == fence->context) {
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/* memory barrier is added by write_seqcount_begin */
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RCU_INIT_POINTER(fobj->shared[i], fence);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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fence_put(old_fence);
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return;
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}
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}
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fence_get(fence);
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fobj->shared[fobj->shared_count] = fence;
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/*
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* make the new fence visible before incrementing
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* fobj->shared_count
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* memory barrier is added by write_seqcount_begin,
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* fobj->shared_count is protected by this lock too
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*/
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smp_wmb();
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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fobj->shared_count++;
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write_seqcount_end(&obj->seq);
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preempt_enable();
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}
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static void
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@ -112,11 +127,12 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
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struct fence *fence)
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{
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unsigned i;
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struct fence *old_fence = NULL;
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fence_get(fence);
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if (!old) {
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fobj->shared[0] = fence;
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RCU_INIT_POINTER(fobj->shared[0], fence);
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fobj->shared_count = 1;
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goto done;
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}
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@ -130,19 +146,38 @@ reservation_object_add_shared_replace(struct reservation_object *obj,
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fobj->shared_count = old->shared_count;
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for (i = 0; i < old->shared_count; ++i) {
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if (fence && old->shared[i]->context == fence->context) {
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fence_put(old->shared[i]);
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fobj->shared[i] = fence;
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fence = NULL;
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struct fence *check;
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check = rcu_dereference_protected(old->shared[i],
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reservation_object_held(obj));
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if (!old_fence && check->context == fence->context) {
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old_fence = check;
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RCU_INIT_POINTER(fobj->shared[i], fence);
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} else
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fobj->shared[i] = old->shared[i];
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RCU_INIT_POINTER(fobj->shared[i], check);
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}
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if (!old_fence) {
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RCU_INIT_POINTER(fobj->shared[fobj->shared_count], fence);
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fobj->shared_count++;
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}
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if (fence)
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fobj->shared[fobj->shared_count++] = fence;
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done:
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obj->fence = fobj;
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kfree(old);
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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/*
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* RCU_INIT_POINTER can be used here,
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* seqcount provides the necessary barriers
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*/
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RCU_INIT_POINTER(obj->fence, fobj);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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if (old)
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kfree_rcu(old, rcu);
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if (old_fence)
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fence_put(old_fence);
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}
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/*
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@ -158,7 +193,7 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
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obj->staged = NULL;
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if (!fobj) {
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BUG_ON(old->shared_count == old->shared_max);
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BUG_ON(old->shared_count >= old->shared_max);
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reservation_object_add_shared_inplace(obj, old, fence);
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} else
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reservation_object_add_shared_replace(obj, old, fobj, fence);
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@ -168,26 +203,275 @@ EXPORT_SYMBOL(reservation_object_add_shared_fence);
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void reservation_object_add_excl_fence(struct reservation_object *obj,
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struct fence *fence)
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{
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struct fence *old_fence = obj->fence_excl;
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struct fence *old_fence = reservation_object_get_excl(obj);
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struct reservation_object_list *old;
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u32 i = 0;
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old = reservation_object_get_list(obj);
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if (old) {
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if (old)
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i = old->shared_count;
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old->shared_count = 0;
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}
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if (fence)
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fence_get(fence);
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obj->fence_excl = fence;
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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/* write_seqcount_begin provides the necessary memory barrier */
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RCU_INIT_POINTER(obj->fence_excl, fence);
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if (old)
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old->shared_count = 0;
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write_seqcount_end(&obj->seq);
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preempt_enable();
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/* inplace update, no shared fences */
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while (i--)
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fence_put(old->shared[i]);
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fence_put(rcu_dereference_protected(old->shared[i],
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reservation_object_held(obj)));
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if (old_fence)
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fence_put(old_fence);
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}
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EXPORT_SYMBOL(reservation_object_add_excl_fence);
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int reservation_object_get_fences_rcu(struct reservation_object *obj,
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struct fence **pfence_excl,
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unsigned *pshared_count,
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struct fence ***pshared)
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{
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unsigned shared_count = 0;
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unsigned retry = 1;
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struct fence **shared = NULL, *fence_excl = NULL;
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int ret = 0;
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while (retry) {
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struct reservation_object_list *fobj;
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unsigned seq;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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fobj = rcu_dereference(obj->fence);
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if (fobj) {
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struct fence **nshared;
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size_t sz = sizeof(*shared) * fobj->shared_max;
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nshared = krealloc(shared, sz,
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GFP_NOWAIT | __GFP_NOWARN);
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if (!nshared) {
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rcu_read_unlock();
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nshared = krealloc(shared, sz, GFP_KERNEL);
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if (nshared) {
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shared = nshared;
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continue;
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}
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ret = -ENOMEM;
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shared_count = 0;
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break;
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}
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shared = nshared;
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memcpy(shared, fobj->shared, sz);
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shared_count = fobj->shared_count;
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} else
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shared_count = 0;
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fence_excl = rcu_dereference(obj->fence_excl);
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retry = read_seqcount_retry(&obj->seq, seq);
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if (retry)
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goto unlock;
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if (!fence_excl || fence_get_rcu(fence_excl)) {
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unsigned i;
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for (i = 0; i < shared_count; ++i) {
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if (fence_get_rcu(shared[i]))
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continue;
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/* uh oh, refcount failed, abort and retry */
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while (i--)
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fence_put(shared[i]);
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if (fence_excl) {
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fence_put(fence_excl);
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fence_excl = NULL;
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}
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retry = 1;
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break;
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}
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} else
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retry = 1;
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unlock:
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rcu_read_unlock();
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}
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*pshared_count = shared_count;
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if (shared_count)
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*pshared = shared;
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else {
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*pshared = NULL;
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kfree(shared);
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}
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*pfence_excl = fence_excl;
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return ret;
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}
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EXPORT_SYMBOL_GPL(reservation_object_get_fences_rcu);
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long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
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bool wait_all, bool intr,
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unsigned long timeout)
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{
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struct fence *fence;
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unsigned seq, shared_count, i = 0;
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long ret = timeout;
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retry:
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fence = NULL;
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shared_count = 0;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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if (wait_all) {
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struct reservation_object_list *fobj = rcu_dereference(obj->fence);
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if (fobj)
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shared_count = fobj->shared_count;
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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for (i = 0; i < shared_count; ++i) {
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struct fence *lfence = rcu_dereference(fobj->shared[i]);
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if (test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags))
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continue;
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if (!fence_get_rcu(lfence))
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goto unlock_retry;
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if (fence_is_signaled(lfence)) {
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fence_put(lfence);
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continue;
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}
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fence = lfence;
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break;
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}
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}
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if (!shared_count) {
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struct fence *fence_excl = rcu_dereference(obj->fence_excl);
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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if (fence_excl &&
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!test_bit(FENCE_FLAG_SIGNALED_BIT, &fence_excl->flags)) {
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if (!fence_get_rcu(fence_excl))
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goto unlock_retry;
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if (fence_is_signaled(fence_excl))
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fence_put(fence_excl);
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else
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fence = fence_excl;
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}
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}
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rcu_read_unlock();
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if (fence) {
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ret = fence_wait_timeout(fence, intr, ret);
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fence_put(fence);
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if (ret > 0 && wait_all && (i + 1 < shared_count))
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goto retry;
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}
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return ret;
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unlock_retry:
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rcu_read_unlock();
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goto retry;
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}
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EXPORT_SYMBOL_GPL(reservation_object_wait_timeout_rcu);
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static inline int
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reservation_object_test_signaled_single(struct fence *passed_fence)
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{
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struct fence *fence, *lfence = passed_fence;
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int ret = 1;
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if (!test_bit(FENCE_FLAG_SIGNALED_BIT, &lfence->flags)) {
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int ret;
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fence = fence_get_rcu(lfence);
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if (!fence)
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return -1;
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ret = !!fence_is_signaled(fence);
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fence_put(fence);
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}
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return ret;
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}
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bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
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bool test_all)
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{
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unsigned seq, shared_count;
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int ret = true;
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retry:
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shared_count = 0;
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seq = read_seqcount_begin(&obj->seq);
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rcu_read_lock();
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if (test_all) {
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unsigned i;
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struct reservation_object_list *fobj = rcu_dereference(obj->fence);
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if (fobj)
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shared_count = fobj->shared_count;
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if (read_seqcount_retry(&obj->seq, seq))
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goto unlock_retry;
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|
||||
for (i = 0; i < shared_count; ++i) {
|
||||
struct fence *fence = rcu_dereference(fobj->shared[i]);
|
||||
|
||||
ret = reservation_object_test_signaled_single(fence);
|
||||
if (ret < 0)
|
||||
goto unlock_retry;
|
||||
else if (!ret)
|
||||
break;
|
||||
}
|
||||
|
||||
/*
|
||||
* There could be a read_seqcount_retry here, but nothing cares
|
||||
* about whether it's the old or newer fence pointers that are
|
||||
* signaled. That race could still have happened after checking
|
||||
* read_seqcount_retry. If you care, use ww_mutex_lock.
|
||||
*/
|
||||
}
|
||||
|
||||
if (!shared_count) {
|
||||
struct fence *fence_excl = rcu_dereference(obj->fence_excl);
|
||||
|
||||
if (read_seqcount_retry(&obj->seq, seq))
|
||||
goto unlock_retry;
|
||||
|
||||
if (fence_excl) {
|
||||
ret = reservation_object_test_signaled_single(fence_excl);
|
||||
if (ret < 0)
|
||||
goto unlock_retry;
|
||||
}
|
||||
}
|
||||
|
||||
rcu_read_unlock();
|
||||
return ret;
|
||||
|
||||
unlock_retry:
|
||||
rcu_read_unlock();
|
||||
goto retry;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(reservation_object_test_signaled_rcu);
|
||||
|
|
|
|||
|
|
@ -28,6 +28,7 @@
|
|||
#include <linux/kref.h>
|
||||
#include <linux/sched.h>
|
||||
#include <linux/printk.h>
|
||||
#include <linux/rcupdate.h>
|
||||
|
||||
struct fence;
|
||||
struct fence_ops;
|
||||
|
|
@ -37,6 +38,7 @@ struct fence_cb;
|
|||
* struct fence - software synchronization primitive
|
||||
* @refcount: refcount for this fence
|
||||
* @ops: fence_ops associated with this fence
|
||||
* @rcu: used for releasing fence with kfree_rcu
|
||||
* @cb_list: list of all callbacks to call
|
||||
* @lock: spin_lock_irqsave used for locking
|
||||
* @context: execution context this fence belongs to, returned by
|
||||
|
|
@ -70,6 +72,7 @@ struct fence_cb;
|
|||
struct fence {
|
||||
struct kref refcount;
|
||||
const struct fence_ops *ops;
|
||||
struct rcu_head rcu;
|
||||
struct list_head cb_list;
|
||||
spinlock_t *lock;
|
||||
unsigned context, seqno;
|
||||
|
|
@ -191,6 +194,20 @@ static inline struct fence *fence_get(struct fence *fence)
|
|||
return fence;
|
||||
}
|
||||
|
||||
/**
|
||||
* fence_get_rcu - get a fence from a reservation_object_list with rcu read lock
|
||||
* @fence: [in] fence to increase refcount of
|
||||
*
|
||||
* Function returns NULL if no refcount could be obtained, or the fence.
|
||||
*/
|
||||
static inline struct fence *fence_get_rcu(struct fence *fence)
|
||||
{
|
||||
if (kref_get_unless_zero(&fence->refcount))
|
||||
return fence;
|
||||
else
|
||||
return NULL;
|
||||
}
|
||||
|
||||
/**
|
||||
* fence_put - decreases refcount of the fence
|
||||
* @fence: [in] fence to reduce refcount of
|
||||
|
|
|
|||
|
|
@ -42,22 +42,29 @@
|
|||
#include <linux/ww_mutex.h>
|
||||
#include <linux/fence.h>
|
||||
#include <linux/slab.h>
|
||||
#include <linux/seqlock.h>
|
||||
#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 {
|
||||
struct rcu_head rcu;
|
||||
u32 shared_count, shared_max;
|
||||
struct fence *shared[];
|
||||
struct fence __rcu *shared[];
|
||||
};
|
||||
|
||||
struct reservation_object {
|
||||
struct ww_mutex lock;
|
||||
seqcount_t seq;
|
||||
|
||||
struct fence *fence_excl;
|
||||
struct reservation_object_list *fence;
|
||||
struct fence __rcu *fence_excl;
|
||||
struct reservation_object_list __rcu *fence;
|
||||
struct reservation_object_list *staged;
|
||||
};
|
||||
|
||||
#define reservation_object_held(obj) lockdep_is_held(&(obj)->lock.base)
|
||||
#define reservation_object_assert_held(obj) \
|
||||
lockdep_assert_held(&(obj)->lock.base)
|
||||
|
||||
|
|
@ -66,8 +73,9 @@ reservation_object_init(struct reservation_object *obj)
|
|||
{
|
||||
ww_mutex_init(&obj->lock, &reservation_ww_class);
|
||||
|
||||
obj->fence_excl = NULL;
|
||||
obj->fence = NULL;
|
||||
__seqcount_init(&obj->seq, reservation_seqcount_string, &reservation_seqcount_class);
|
||||
RCU_INIT_POINTER(obj->fence, NULL);
|
||||
RCU_INIT_POINTER(obj->fence_excl, NULL);
|
||||
obj->staged = NULL;
|
||||
}
|
||||
|
||||
|
|
@ -76,18 +84,20 @@ reservation_object_fini(struct reservation_object *obj)
|
|||
{
|
||||
int i;
|
||||
struct reservation_object_list *fobj;
|
||||
struct fence *excl;
|
||||
|
||||
/*
|
||||
* This object should be dead and all references must have
|
||||
* been released to it.
|
||||
* been released to it, so no need to be protected with rcu.
|
||||
*/
|
||||
if (obj->fence_excl)
|
||||
fence_put(obj->fence_excl);
|
||||
excl = rcu_dereference_protected(obj->fence_excl, 1);
|
||||
if (excl)
|
||||
fence_put(excl);
|
||||
|
||||
fobj = obj->fence;
|
||||
fobj = rcu_dereference_protected(obj->fence, 1);
|
||||
if (fobj) {
|
||||
for (i = 0; i < fobj->shared_count; ++i)
|
||||
fence_put(fobj->shared[i]);
|
||||
fence_put(rcu_dereference_protected(fobj->shared[i], 1));
|
||||
|
||||
kfree(fobj);
|
||||
}
|
||||
|
|
@ -99,17 +109,15 @@ reservation_object_fini(struct reservation_object *obj)
|
|||
static inline struct reservation_object_list *
|
||||
reservation_object_get_list(struct reservation_object *obj)
|
||||
{
|
||||
reservation_object_assert_held(obj);
|
||||
|
||||
return obj->fence;
|
||||
return rcu_dereference_protected(obj->fence,
|
||||
reservation_object_held(obj));
|
||||
}
|
||||
|
||||
static inline struct fence *
|
||||
reservation_object_get_excl(struct reservation_object *obj)
|
||||
{
|
||||
reservation_object_assert_held(obj);
|
||||
|
||||
return obj->fence_excl;
|
||||
return rcu_dereference_protected(obj->fence_excl,
|
||||
reservation_object_held(obj));
|
||||
}
|
||||
|
||||
int reservation_object_reserve_shared(struct reservation_object *obj);
|
||||
|
|
@ -119,4 +127,16 @@ void reservation_object_add_shared_fence(struct reservation_object *obj,
|
|||
void reservation_object_add_excl_fence(struct reservation_object *obj,
|
||||
struct fence *fence);
|
||||
|
||||
int reservation_object_get_fences_rcu(struct reservation_object *obj,
|
||||
struct fence **pfence_excl,
|
||||
unsigned *pshared_count,
|
||||
struct fence ***pshared);
|
||||
|
||||
long reservation_object_wait_timeout_rcu(struct reservation_object *obj,
|
||||
bool wait_all, bool intr,
|
||||
unsigned long timeout);
|
||||
|
||||
bool reservation_object_test_signaled_rcu(struct reservation_object *obj,
|
||||
bool test_all);
|
||||
|
||||
#endif /* _LINUX_RESERVATION_H */
|
||||
|
|
|
|||
Loading…
Reference in New Issue