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Commit 8ba9153b authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Remove lock-acquisition loop from rcu_read_unlock_special() 



Several releases have come and gone without the warning triggering,
so remove the lock-acquisition loop.  Retain the WARN_ON_ONCE()
out of sheer paranoia.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent fecbf6f0

kernel/rcu/tree_plugin.h

+6 −12
Original line number Diff line number Diff line
@@ -449,19 +449,13 @@ void rcu_read_unlock_special(struct task_struct *t) 


		/*

		 * Remove this task from the list it blocked on.  The task

		 * now remains queued on the rcu_node corresponding to

		 * the CPU it first blocked on, so the first attempt to

		 * acquire the task's rcu_node's ->lock will succeed.

		 * Keep the loop and add a WARN_ON() out of sheer paranoia.

		 * now remains queued on the rcu_node corresponding to the

		 * CPU it first blocked on, so there is no longer any need

		 * to loop.  Retain a WARN_ON_ONCE() out of sheer paranoia.

		 */

		for (;;) {

		rnp = t->rcu_blocked_node;

		raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */

			if (rnp == t->rcu_blocked_node)

				break;

			WARN_ON_ONCE(1);

			raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */

		}

		WARN_ON_ONCE(rnp != t->rcu_blocked_node);

		empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);

		empty_exp = sync_rcu_preempt_exp_done(rnp);

		smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */