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: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index 3bc4b3d..24343eb 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -385,17 +385,16 @@
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);
+ goto retry_ipi;
}
+ /* 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);