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rcu: Remove lock-acquisition loop from rcu_read_unlock_special()

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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>
This commit is contained in:
Paul E. McKenney 2015-09-29 07:55:41 -07:00
parent fecbf6f01f
commit 8ba9153b2c
1 changed files with 6 additions and 12 deletions
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18
kernel/rcu/tree_plugin.h
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@ -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. */
}
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. */