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rcu: Reduce latency of rcu_prepare_for_idle()

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Re-enable interrupts across calls to quiescent-state functions and
also across force_quiescent_state() to reduce latency.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2011-11-22 21:08:13 -08:00 committed by Paul E. McKenney
parent f535a607c1
commit 3ad0decf98
1 changed files with 7 additions and 5 deletions
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12
kernel/rcutree_plugin.h
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@ -2009,7 +2009,6 @@ int rcu_needs_cpu(int cpu)
*/ */
static void rcu_prepare_for_idle(int cpu) static void rcu_prepare_for_idle(int cpu)
{ {
int c = 0;
unsigned long flags; unsigned long flags;
local_irq_save(flags); local_irq_save(flags);
@ -2055,27 +2054,30 @@ static void rcu_prepare_for_idle(int cpu)
*/ */
#ifdef CONFIG_TREE_PREEMPT_RCU #ifdef CONFIG_TREE_PREEMPT_RCU
if (per_cpu(rcu_preempt_data, cpu).nxtlist) { if (per_cpu(rcu_preempt_data, cpu).nxtlist) {
local_irq_restore(flags);
rcu_preempt_qs(cpu); rcu_preempt_qs(cpu);
force_quiescent_state(&rcu_preempt_state, 0); force_quiescent_state(&rcu_preempt_state, 0);
c = c || per_cpu(rcu_preempt_data, cpu).nxtlist; local_irq_save(flags);
} }
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
if (per_cpu(rcu_sched_data, cpu).nxtlist) { if (per_cpu(rcu_sched_data, cpu).nxtlist) {
local_irq_restore(flags);
rcu_sched_qs(cpu); rcu_sched_qs(cpu);
force_quiescent_state(&rcu_sched_state, 0); force_quiescent_state(&rcu_sched_state, 0);
c = c || per_cpu(rcu_sched_data, cpu).nxtlist; local_irq_save(flags);
} }
if (per_cpu(rcu_bh_data, cpu).nxtlist) { if (per_cpu(rcu_bh_data, cpu).nxtlist) {
local_irq_restore(flags);
rcu_bh_qs(cpu); rcu_bh_qs(cpu);
force_quiescent_state(&rcu_bh_state, 0); force_quiescent_state(&rcu_bh_state, 0);
c = c || per_cpu(rcu_bh_data, cpu).nxtlist; local_irq_save(flags);
} }
/* /*
* If RCU callbacks are still pending, RCU still needs this CPU. * If RCU callbacks are still pending, RCU still needs this CPU.
* So try forcing the callbacks through the grace period. * So try forcing the callbacks through the grace period.
*/ */
if (c) { if (rcu_cpu_has_callbacks(cpu)) {
local_irq_restore(flags); local_irq_restore(flags);
trace_rcu_prep_idle("More callbacks"); trace_rcu_prep_idle("More callbacks");
invoke_rcu_core(); invoke_rcu_core();