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Commit b6a932d1 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Make rcu_read_unlock_special() propagate ->qsmaskinit bit clearing 



This commit causes rcu_read_unlock_special() to propagate ->qsmaskinit
bit clearing up the rcu_node tree once a given rcu_node structure's
blkd_tasks list becomes empty.  This is the final commit in preparation
for the rework of RCU priority boosting:  It enables preempted tasks to
remain queued on their rcu_node structure even after all of that rcu_node
structure's CPUs have gone offline.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 8af3a5e7

kernel/rcu/tree.c

+4 −0
Original line number Diff line number Diff line
@@ -2329,6 +2329,10 @@ static void rcu_cleanup_dying_cpu(struct rcu_state *rsp) 
{

}



static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)

{

}



static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)

{

}

kernel/rcu/tree_plugin.h

+13 −3
Original line number Diff line number Diff line
@@ -322,9 +322,10 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp) 
 */

void rcu_read_unlock_special(struct task_struct *t)

{

	int empty_exp;

	int empty_norm;

	int empty_exp_now;

	bool empty;

	bool empty_exp;

	bool empty_norm;

	bool empty_exp_now;

	unsigned long flags;

	struct list_head *np;

#ifdef CONFIG_RCU_BOOST
@@ -376,6 +377,7 @@ void rcu_read_unlock_special(struct task_struct *t) 
				break;

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

		}

		empty = !rcu_preempt_has_tasks(rnp);

		empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);

		empty_exp = !rcu_preempted_readers_exp(rnp);

		smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
@@ -395,6 +397,14 @@ void rcu_read_unlock_special(struct task_struct *t) 
		drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;

#endif /* #ifdef CONFIG_RCU_BOOST */



		/*

		 * If this was the last task on the list, go see if we

		 * need to propagate ->qsmaskinit bit clearing up the

		 * rcu_node tree.

		 */

		if (!empty && !rcu_preempt_has_tasks(rnp))

			rcu_cleanup_dead_rnp(rnp);



		/*

		 * If this was the last task on the current list, and if

		 * we aren't waiting on any CPUs, report the quiescent state.