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rcu: ignore offline CPUs in last non-dyntick-idle CPU check
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Offline CPUs are not in nohz_cpu_mask, but can be ignored when checking
for the last non-dyntick-idle CPU.  This patch therefore only checks
online CPUs for not being dyntick idle, allowing fast entry into
full-system dyntick-idle state even when there are some offline CPUs.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Lai Jiangshan authored and Paul E. McKenney committed May 10, 2010
1 parent 0c34029 commit 5db3567
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion kernel/rcutree_plugin.h
Original file line number Diff line number Diff line change
Expand Up @@ -1016,7 +1016,7 @@ int rcu_needs_cpu(int cpu)

/* Don't bother unless we are the last non-dyntick-idle CPU. */
for_each_cpu_not(thatcpu, nohz_cpu_mask)
if (thatcpu != cpu) {
if (cpu_online(thatcpu) && thatcpu != cpu) {
per_cpu(rcu_dyntick_drain, cpu) = 0;
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
return rcu_needs_cpu_quick_check(cpu);
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