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Commit ec6c676a authored Feb 17, 2014 by Paul E. McKenney Committed by Jens Axboe Feb 18, 2014

block: Substitute rcu_access_pointer() for rcu_dereference_raw()



(Trivial patch.)

If the code is looking at the RCU-protected pointer itself, but not
dereferencing it, the rcu_dereference() functions can be downgraded to
rcu_access_pointer().  This commit makes this downgrade in blkg_destroy()
and ioc_destroy_icq(), both of which simply compare the RCU-protected
pointer against another pointer with no dereferencing.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Jens Axboe <axboe@fb.com>

parent e3ebf0d4

block/blk-cgroup.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -336,7 +336,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
		* under queue_lock. If it's not pointing to @blkg now, it never
		* will. Hint assignment itself can race safely.
		*/
		if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
		if (rcu_access_pointer(blkcg->blkg_hint) == blkg)
		rcu_assign_pointer(blkcg->blkg_hint, NULL);

		/*

block/blk-ioc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -68,7 +68,7 @@ static void ioc_destroy_icq(struct io_cq *icq)
		* under queue_lock. If it's not pointing to @icq now, it never
		* will. Hint assignment itself can race safely.
		*/
		if (rcu_dereference_raw(ioc->icq_hint) == icq)
		if (rcu_access_pointer(ioc->icq_hint) == icq)
		rcu_assign_pointer(ioc->icq_hint, NULL);

		ioc_exit_icq(icq);