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Commit 4f89b336 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
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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: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 70321d44

kernel/rcutiny_plugin.h

+2 −2
Original line number Diff line number Diff line
@@ -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;

}



/*

kernel/rcutree_plugin.h

+2 −1
Original line number Diff line number Diff line
@@ -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;

}



/*