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rcu: Use RCU's online-CPU state for expedited IPI retry

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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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2016-06-30 12:16:11 -07:00
parent 98834b8378
commit 385c859f67
1 changed files with 5 additions and 6 deletions
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11
kernel/rcu/tree_exp.h
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@@ -385,17 +385,16 @@ retry_ipi:
mask_ofl_ipi &= ~mask; mask_ofl_ipi &= ~mask;
continue; continue;
} }
/* Failed, raced with offline. */ /* Failed, raced with CPU hotplug operation. */
raw_spin_lock_irqsave_rcu_node(rnp, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (cpu_online(cpu) && if ((rnp->qsmaskinitnext & mask) &&
(rnp->expmask & mask)) { (rnp->expmask & mask)) {
/* Online, so delay for a bit and try again. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
schedule_timeout_uninterruptible(1); schedule_timeout_uninterruptible(1);
if (cpu_online(cpu) && goto retry_ipi;
(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)) if (!(rnp->expmask & mask))
mask_ofl_ipi &= ~mask; mask_ofl_ipi &= ~mask;
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); raw_spin_unlock_irqrestore_rcu_node(rnp, flags);