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rcu: Apply ACCESS_ONCE() to rcu_boost() return value 

Both TINY_RCU's and TREE_RCU's implementations of rcu_boost() access
the ->boost_tasks and ->exp_tasks fields without preventing concurrent
changes to these fields.  This commit therefore applies ACCESS_ONCE in
order to prevent compiler mischief.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
hifive-unleashed-5.1
Paul E. McKenney 2011-12-09 14:43:47 -08:00 committed by Paul E. McKenney
parent 70321d447a
commit 4f89b336fd
2 changed files with 4 additions and 3 deletions
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4
kernel/rcutiny_plugin.h
View File

@ -312,8 +312,8 @@ static int rcu_boost(void)
rt_mutex_lock(&mtx);
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */
return rcu_preempt_ctrlblk.boost_tasks != NULL ||
rcu_preempt_ctrlblk.exp_tasks != NULL;
return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL ||
ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL;
}
/*

3
kernel/rcutree_plugin.h
View File

@ -1232,7 +1232,8 @@ static int rcu_boost(struct rcu_node *rnp)
rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */
rt_mutex_unlock(&mtx); /* Keep lockdep happy. */
return rnp->exp_tasks != NULL || rnp->boost_tasks != NULL;
return ACCESS_ONCE(rnp->exp_tasks) != NULL ||
ACCESS_ONCE(rnp->boost_tasks) != NULL;
}
/*