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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 57ba873..ae4ce2b 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -449,19 +449,13 @@
/*
* 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. */
- }
+ rnp = t->rcu_blocked_node;
+ raw_spin_lock_rcu_node(rnp); /* irqs already 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. */
