dma-buf: Restore seqlock around dma_resv updates
This reverts67c97fb79a("dma-buf: add reservation_object_fences helper")dd7a7d1ff2("drm/i915: use new reservation_object_fences helper")0e1d8083bd("dma-buf: further relax reservation_object_add_shared_fence")5d344f58da("dma-buf: nuke reservation_object seq number") The scenario that defeats simply grabbing a set of shared/exclusive fences and using them blissfully under RCU is that any of those fences may be reallocated by a SLAB_TYPESAFE_BY_RCU fence slab cache. In this scenario, while keeping the rcu_read_lock we need to establish that no fence was changed in the dma_resv after a read (or full) memory barrier. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Acked-by: Christian König <christian.koenig@amd.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190814182401.25009-1-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson
Родитель
dc2e1e5b27
Коммит
b016cd6ed4
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@ -199,7 +199,7 @@ static __poll_t dma_buf_poll(struct file *file, poll_table *poll)
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struct dma_resv_list *fobj;
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struct dma_fence *fence_excl;
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__poll_t 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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@ -213,8 +213,21 @@ static __poll_t 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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retry:
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seq = read_seqcount_begin(&resv->seq);
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rcu_read_lock();
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dma_resv_fences(resv, &fence_excl, &fobj, &shared_count);
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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 & EPOLLOUT) || shared_count == 0)) {
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struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
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__poll_t pevents = EPOLLIN;
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@ -1144,6 +1157,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
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struct dma_resv *robj;
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struct dma_resv_list *fobj;
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struct dma_fence *fence;
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unsigned seq;
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int count = 0, attach_count, shared_count, i;
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size_t size = 0;
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@ -1174,9 +1188,16 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
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buf_obj->name ?: "");
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robj = buf_obj->resv;
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rcu_read_lock();
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dma_resv_fences(robj, &fence, &fobj, &shared_count);
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rcu_read_unlock();
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while (true) {
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seq = read_seqcount_begin(&robj->seq);
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rcu_read_lock();
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fobj = rcu_dereference(robj->fence);
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shared_count = fobj ? fobj->shared_count : 0;
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fence = rcu_dereference(robj->fence_excl);
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if (!read_seqcount_retry(&robj->seq, seq))
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break;
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rcu_read_unlock();
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}
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if (fence)
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seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
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@ -49,6 +49,12 @@
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DEFINE_WD_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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* dma_resv_list_alloc - allocate fence list
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* @shared_max: number of fences we need space for
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@ -96,6 +102,9 @@ static void dma_resv_list_free(struct dma_resv_list *list)
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void dma_resv_init(struct dma_resv *obj)
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{
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ww_mutex_init(&obj->lock, &reservation_ww_class);
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__seqcount_init(&obj->seq, reservation_seqcount_string,
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&reservation_seqcount_class);
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RCU_INIT_POINTER(obj->fence, NULL);
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RCU_INIT_POINTER(obj->fence_excl, NULL);
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}
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@ -225,6 +234,9 @@ void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence)
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fobj = dma_resv_get_list(obj);
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count = fobj->shared_count;
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preempt_disable();
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write_seqcount_begin(&obj->seq);
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for (i = 0; i < count; ++i) {
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old = rcu_dereference_protected(fobj->shared[i],
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@ -242,6 +254,9 @@ replace:
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RCU_INIT_POINTER(fobj->shared[i], fence);
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/* pointer update must be visible before we extend the shared_count */
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smp_store_mb(fobj->shared_count, count);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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dma_fence_put(old);
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}
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EXPORT_SYMBOL(dma_resv_add_shared_fence);
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@ -269,10 +284,12 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
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dma_fence_get(fence);
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preempt_disable();
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rcu_assign_pointer(obj->fence_excl, fence);
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/* pointer update must be visible before we modify the shared_count */
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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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smp_store_mb(old->shared_count, 0);
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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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@ -295,15 +312,17 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
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{
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struct dma_resv_list *src_list, *dst_list;
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struct dma_fence *old, *new;
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unsigned int i, shared_count;
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unsigned i;
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dma_resv_assert_held(dst);
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rcu_read_lock();
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src_list = rcu_dereference(src->fence);
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retry:
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dma_resv_fences(src, &new, &src_list, &shared_count);
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if (shared_count) {
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if (src_list) {
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unsigned shared_count = src_list->shared_count;
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rcu_read_unlock();
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dst_list = dma_resv_list_alloc(shared_count);
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@ -311,14 +330,14 @@ retry:
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return -ENOMEM;
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rcu_read_lock();
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dma_resv_fences(src, &new, &src_list, &shared_count);
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if (!src_list || shared_count > dst_list->shared_max) {
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src_list = rcu_dereference(src->fence);
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if (!src_list || src_list->shared_count > shared_count) {
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kfree(dst_list);
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goto retry;
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}
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dst_list->shared_count = 0;
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for (i = 0; i < shared_count; ++i) {
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for (i = 0; i < src_list->shared_count; ++i) {
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struct dma_fence *fence;
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fence = rcu_dereference(src_list->shared[i]);
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@ -328,6 +347,7 @@ retry:
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if (!dma_fence_get_rcu(fence)) {
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dma_resv_list_free(dst_list);
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src_list = rcu_dereference(src->fence);
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goto retry;
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}
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@ -342,18 +362,18 @@ retry:
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dst_list = NULL;
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}
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if (new && !dma_fence_get_rcu(new)) {
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dma_resv_list_free(dst_list);
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goto retry;
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}
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new = dma_fence_get_rcu_safe(&src->fence_excl);
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rcu_read_unlock();
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src_list = dma_resv_get_list(dst);
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old = dma_resv_get_excl(dst);
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preempt_disable();
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rcu_assign_pointer(dst->fence_excl, new);
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rcu_assign_pointer(dst->fence, dst_list);
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write_seqcount_begin(&dst->seq);
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/* write_seqcount_begin provides the necessary memory barrier */
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RCU_INIT_POINTER(dst->fence_excl, new);
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RCU_INIT_POINTER(dst->fence, dst_list);
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write_seqcount_end(&dst->seq);
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preempt_enable();
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dma_resv_list_free(src_list);
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@ -388,18 +408,19 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
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do {
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struct dma_resv_list *fobj;
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unsigned int i;
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unsigned int i, seq;
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size_t sz = 0;
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i = 0;
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shared_count = i = 0;
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rcu_read_lock();
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dma_resv_fences(obj, &fence_excl, &fobj,
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&shared_count);
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seq = read_seqcount_begin(&obj->seq);
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fence_excl = rcu_dereference(obj->fence_excl);
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if (fence_excl && !dma_fence_get_rcu(fence_excl))
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goto unlock;
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fobj = rcu_dereference(obj->fence);
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if (fobj)
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sz += sizeof(*shared) * fobj->shared_max;
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@ -427,6 +448,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
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break;
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}
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shared = nshared;
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shared_count = fobj ? fobj->shared_count : 0;
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for (i = 0; i < shared_count; ++i) {
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shared[i] = rcu_dereference(fobj->shared[i]);
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if (!dma_fence_get_rcu(shared[i]))
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@ -434,7 +456,7 @@ int dma_resv_get_fences_rcu(struct dma_resv *obj,
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}
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}
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if (i != shared_count) {
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if (i != shared_count || read_seqcount_retry(&obj->seq, seq)) {
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while (i--)
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dma_fence_put(shared[i]);
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dma_fence_put(fence_excl);
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@ -478,17 +500,18 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *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 dma_resv_list *fobj;
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struct dma_fence *fence;
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unsigned shared_count;
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unsigned seq, shared_count;
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long ret = timeout ? timeout : 1;
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int i;
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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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i = -1;
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dma_resv_fences(obj, &fence, &fobj, &shared_count);
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fence = rcu_dereference(obj->fence_excl);
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if (fence && !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
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if (!dma_fence_get_rcu(fence))
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goto unlock_retry;
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@ -503,6 +526,11 @@ retry:
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}
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if (wait_all) {
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struct dma_resv_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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for (i = 0; !fence && i < shared_count; ++i) {
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struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
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@ -525,6 +553,11 @@ retry:
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rcu_read_unlock();
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if (fence) {
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if (read_seqcount_retry(&obj->seq, seq)) {
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dma_fence_put(fence);
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goto retry;
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}
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ret = dma_fence_wait_timeout(fence, intr, ret);
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dma_fence_put(fence);
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if (ret > 0 && wait_all && (i + 1 < shared_count))
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@ -567,19 +600,23 @@ static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
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*/
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bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
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{
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struct dma_resv_list *fobj;
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struct dma_fence *fence_excl;
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unsigned shared_count;
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unsigned seq, shared_count;
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int ret;
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rcu_read_lock();
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retry:
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ret = true;
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shared_count = 0;
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seq = read_seqcount_begin(&obj->seq);
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dma_resv_fences(obj, &fence_excl, &fobj, &shared_count);
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if (test_all) {
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unsigned i;
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struct dma_resv_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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for (i = 0; i < shared_count; ++i) {
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struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
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@ -589,12 +626,22 @@ retry:
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else if (!ret)
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break;
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}
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if (read_seqcount_retry(&obj->seq, seq))
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goto retry;
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}
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if (!shared_count && fence_excl) {
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ret = dma_resv_test_signaled_single(fence_excl);
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if (ret < 0)
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goto retry;
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if (!shared_count) {
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struct dma_fence *fence_excl = rcu_dereference(obj->fence_excl);
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if (fence_excl) {
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ret = dma_resv_test_signaled_single(fence_excl);
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if (ret < 0)
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goto retry;
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if (read_seqcount_retry(&obj->seq, seq))
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goto retry;
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}
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}
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rcu_read_unlock();
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@ -251,7 +251,12 @@ static int amdgpu_amdkfd_remove_eviction_fence(struct amdgpu_bo *bo,
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new->shared_max = old->shared_max;
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new->shared_count = k;
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rcu_assign_pointer(resv->fence, new);
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/* Install the new fence list, seqcount provides the barriers */
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preempt_disable();
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write_seqcount_begin(&resv->seq);
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RCU_INIT_POINTER(resv->fence, new);
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write_seqcount_end(&resv->seq);
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preempt_enable();
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/* Drop the references to the removed fences or move them to ef_list */
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for (i = j, k = 0; i < old->shared_count; ++i) {
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|
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@ -83,8 +83,7 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
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struct drm_i915_gem_busy *args = data;
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struct drm_i915_gem_object *obj;
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struct dma_resv_list *list;
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unsigned int i, shared_count;
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struct dma_fence *excl;
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unsigned int seq;
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int err;
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err = -ENOENT;
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@ -110,18 +109,29 @@ i915_gem_busy_ioctl(struct drm_device *dev, void *data,
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* to report the overall busyness. This is what the wait-ioctl does.
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*
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*/
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dma_resv_fences(obj->base.resv, &excl, &list, &shared_count);
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retry:
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seq = raw_read_seqcount(&obj->base.resv->seq);
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/* Translate the exclusive fence to the READ *and* WRITE engine */
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args->busy = busy_check_writer(excl);
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args->busy =
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busy_check_writer(rcu_dereference(obj->base.resv->fence_excl));
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|
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/* Translate shared fences to READ set of engines */
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for (i = 0; i < shared_count; ++i) {
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struct dma_fence *fence = rcu_dereference(list->shared[i]);
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list = rcu_dereference(obj->base.resv->fence);
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if (list) {
|
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unsigned int shared_count = list->shared_count, i;
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|
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args->busy |= busy_check_reader(fence);
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for (i = 0; i < shared_count; ++i) {
|
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struct dma_fence *fence =
|
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rcu_dereference(list->shared[i]);
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args->busy |= busy_check_reader(fence);
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}
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}
|
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|
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if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
|
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goto retry;
|
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|
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err = 0;
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out:
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rcu_read_unlock();
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|
|
|
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|
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@ -46,6 +46,8 @@
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#include <linux/rcupdate.h>
|
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|
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extern struct ww_class reservation_ww_class;
|
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extern struct lock_class_key reservation_seqcount_class;
|
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extern const char reservation_seqcount_string[];
|
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|
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/**
|
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* struct dma_resv_list - a list of shared fences
|
||||
|
|
@ -69,6 +71,7 @@ struct dma_resv_list {
|
|||
*/
|
||||
struct dma_resv {
|
||||
struct ww_mutex lock;
|
||||
seqcount_t seq;
|
||||
|
||||
struct dma_fence __rcu *fence_excl;
|
||||
struct dma_resv_list __rcu *fence;
|
||||
|
|
@ -77,24 +80,6 @@ struct dma_resv {
|
|||
#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
|
||||
#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
|
||||
|
||||
/**
|
||||
* dma_resv_get_excl - get the reservation object's
|
||||
* exclusive fence, with update-side lock held
|
||||
* @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 or NULL
|
||||
*/
|
||||
static inline struct dma_fence *dma_resv_get_excl(struct dma_resv *obj)
|
||||
{
|
||||
return rcu_dereference_protected(obj->fence_excl,
|
||||
dma_resv_held(obj));
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_get_list - get the reservation object's
|
||||
* shared fence list, with update-side lock held
|
||||
|
|
@ -109,53 +94,6 @@ static inline struct dma_resv_list *dma_resv_get_list(struct dma_resv *obj)
|
|||
dma_resv_held(obj));
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_fences - read consistent fence pointers
|
||||
* @obj: reservation object where we get the fences from
|
||||
* @excl: pointer for the exclusive fence
|
||||
* @list: pointer for the shared fence list
|
||||
*
|
||||
* Make sure we have a consisten exclusive fence and shared fence list.
|
||||
* Must be called with rcu read side lock held.
|
||||
*/
|
||||
static inline void dma_resv_fences(struct dma_resv *obj,
|
||||
struct dma_fence **excl,
|
||||
struct dma_resv_list **list,
|
||||
u32 *shared_count)
|
||||
{
|
||||
do {
|
||||
*excl = rcu_dereference(obj->fence_excl);
|
||||
*list = rcu_dereference(obj->fence);
|
||||
*shared_count = *list ? (*list)->shared_count : 0;
|
||||
smp_rmb(); /* See dma_resv_add_excl_fence */
|
||||
} while (rcu_access_pointer(obj->fence_excl) != *excl);
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_get_excl_rcu - get the reservation object's
|
||||
* exclusive fence, without lock held.
|
||||
* @obj: the reservation object
|
||||
*
|
||||
* If there is an exclusive fence, this atomically increments it's
|
||||
* reference count and returns it.
|
||||
*
|
||||
* RETURNS
|
||||
* The exclusive fence or NULL if none
|
||||
*/
|
||||
static inline struct dma_fence *dma_resv_get_excl_rcu(struct dma_resv *obj)
|
||||
{
|
||||
struct dma_fence *fence;
|
||||
|
||||
if (!rcu_access_pointer(obj->fence_excl))
|
||||
return NULL;
|
||||
|
||||
rcu_read_lock();
|
||||
fence = dma_fence_get_rcu_safe(&obj->fence_excl);
|
||||
rcu_read_unlock();
|
||||
|
||||
return fence;
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_lock - lock the reservation object
|
||||
* @obj: the reservation object
|
||||
|
|
@ -290,6 +228,51 @@ static inline void dma_resv_unlock(struct dma_resv *obj)
|
|||
ww_mutex_unlock(&obj->lock);
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_get_excl - get the reservation object's
|
||||
* exclusive fence, with update-side lock held
|
||||
* @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 or NULL
|
||||
*/
|
||||
static inline struct dma_fence *
|
||||
dma_resv_get_excl(struct dma_resv *obj)
|
||||
{
|
||||
return rcu_dereference_protected(obj->fence_excl,
|
||||
dma_resv_held(obj));
|
||||
}
|
||||
|
||||
/**
|
||||
* dma_resv_get_excl_rcu - get the reservation object's
|
||||
* exclusive fence, without lock held.
|
||||
* @obj: the reservation object
|
||||
*
|
||||
* If there is an exclusive fence, this atomically increments it's
|
||||
* reference count and returns it.
|
||||
*
|
||||
* RETURNS
|
||||
* The exclusive fence or NULL if none
|
||||
*/
|
||||
static inline struct dma_fence *
|
||||
dma_resv_get_excl_rcu(struct dma_resv *obj)
|
||||
{
|
||||
struct dma_fence *fence;
|
||||
|
||||
if (!rcu_access_pointer(obj->fence_excl))
|
||||
return NULL;
|
||||
|
||||
rcu_read_lock();
|
||||
fence = dma_fence_get_rcu_safe(&obj->fence_excl);
|
||||
rcu_read_unlock();
|
||||
|
||||
return fence;
|
||||
}
|
||||
|
||||
void dma_resv_init(struct dma_resv *obj);
|
||||
void dma_resv_fini(struct dma_resv *obj);
|
||||
int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences);
|
||||
|
|
|
|||
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