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dma-buf: Relax the write-seqlock for reallocating the shared fence list
As the set of shared fences is not being changed during reallocation of the reservation list, we can skip updating the write_seqlock. Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Christian König <christian.koenig@amd.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: https://patchwork.freedesktop.org/patch/msgid/20190712080314.21018-2-chris@chris-wilson.co.uk
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1 changed files with 7 additions and 7 deletions
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@ -157,15 +157,15 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
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(ksize(new) - offsetof(typeof(*new), shared)) /
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sizeof(*new->shared);
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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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* We are not changing the effective set of fences here so can
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* merely update the pointer to the new array; both existing
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* readers and new readers will see exactly the same set of
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* active (unsignaled) shared fences. Individual fences and the
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* old array are protected by RCU and so will not vanish under
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* the gaze of the rcu_read_lock() readers.
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*/
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RCU_INIT_POINTER(obj->fence, new);
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write_seqcount_end(&obj->seq);
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preempt_enable();
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rcu_assign_pointer(obj->fence, new);
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if (!old)
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return 0;
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