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Commit 385c859f authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Use RCU's online-CPU state for expedited IPI retry 



This commit improves the accuracy of the interaction between CPU hotplug
operations and RCU's expedited grace periods by using RCU's online-CPU
state to determine when failed IPIs should be retried.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 98834b83

kernel/rcu/tree_exp.h

+5 −6
Original line number Diff line number Diff line
@@ -385,17 +385,16 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, 
				mask_ofl_ipi &= ~mask;

				continue;

			}

			/* Failed, raced with offline. */

			/* Failed, raced with CPU hotplug operation. */

			raw_spin_lock_irqsave_rcu_node(rnp, flags);

			if (cpu_online(cpu) &&

			if ((rnp->qsmaskinitnext & mask) &&

			    (rnp->expmask & mask)) {

				/* Online, so delay for a bit and try again. */

				raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

				schedule_timeout_uninterruptible(1);

				if (cpu_online(cpu) &&

				    (rnp->expmask & mask))

				goto retry_ipi;

				raw_spin_lock_irqsave_rcu_node(rnp, flags);

			}

			/* CPU really is offline, so we can ignore it. */

			if (!(rnp->expmask & mask))

				mask_ofl_ipi &= ~mask;

			raw_spin_unlock_irqrestore_rcu_node(rnp, flags);