dma-buf: Relax the write-seqlock for reallocating the shared fence list (30fe7b07) · Commits · 戴 / test

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:

drivers/dma-buf/reservation.c

+7 −7

Original line number	Diff line number	Diff line
		@@ -157,15 +157,15 @@ int reservation_object_reserve_shared(struct reservation_object *obj,
		(ksize(new) - offsetof(typeof(*new), shared)) /
		sizeof(*new->shared);

		preempt_disable();
		write_seqcount_begin(&obj->seq);
		/*
		* RCU_INIT_POINTER can be used here,
		* seqcount provides the necessary barriers
		* We are not changing the effective set of fences here so can
		* merely update the pointer to the new array; both existing
		* readers and new readers will see exactly the same set of
		* active (unsignaled) shared fences. Individual fences and the
		* old array are protected by RCU and so will not vanish under
		* the gaze of the rcu_read_lock() readers.
		*/
		RCU_INIT_POINTER(obj->fence, new);
		write_seqcount_end(&obj->seq);
		preempt_enable();
		rcu_assign_pointer(obj->fence, new);

		if (!old)
		return 0;