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dma-buf: nuke reservation_object seq number
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. v2: switch setting excl fence to rcu_assign_pointer Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/322380/
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@ -49,12 +49,6 @@
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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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* reservation_object_list_alloc - allocate fence list
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* @shared_max: number of fences we need space for
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@ -103,9 +97,6 @@ static void reservation_object_list_free(struct reservation_object_list *list)
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void reservation_object_init(struct reservation_object *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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@ -282,12 +273,10 @@ void reservation_object_add_excl_fence(struct reservation_object *obj,
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dma_fence_get(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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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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if (old)
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old->shared_count = 0;
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write_seqcount_end(&obj->seq);
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smp_store_mb(old->shared_count, 0);
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preempt_enable();
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/* inplace update, no shared fences */
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@ -368,11 +357,8 @@ retry:
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old = reservation_object_get_excl(dst);
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preempt_disable();
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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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rcu_assign_pointer(dst->fence_excl, new);
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rcu_assign_pointer(dst->fence, dst_list);
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preempt_enable();
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reservation_object_list_free(src_list);
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@ -46,8 +46,6 @@
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#include <linux/rcupdate.h>
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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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* struct reservation_object_list - a list of shared fences
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@ -71,7 +69,6 @@ struct reservation_object_list {
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*/
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struct reservation_object {
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struct ww_mutex lock;
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seqcount_t seq;
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struct dma_fence __rcu *fence_excl;
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struct reservation_object_list __rcu *fence;
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@ -130,14 +127,12 @@ reservation_object_fences(struct reservation_object *obj,
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struct reservation_object_list **list,
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u32 *shared_count)
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{
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unsigned int seq;
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do {
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seq = read_seqcount_begin(&obj->seq);
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*excl = rcu_dereference(obj->fence_excl);
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*list = rcu_dereference(obj->fence);
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*shared_count = *list ? (*list)->shared_count : 0;
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} while (read_seqcount_retry(&obj->seq, seq));
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smp_rmb(); /* See reservation_object_add_excl_fence */
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} while (rcu_access_pointer(obj->fence_excl) != *excl);
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}
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/**
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