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Subject[PATCH tip/core/rcu 37/47] rcu: No interrupt disabling for rcu_prepare_for_idle()
Date
From: "Paul E. McKenney" <paul.mckenney@linaro.org>

The rcu_prepare_for_idle() function is always called with interrupts
disabled, so there is no reason to disable interrupts again within
rcu_prepare_for_idle(). Therefore, this commit removes all of the
interrupt disabling, also removing a latent disabling-unbalance bug.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcutree_plugin.h | 18 +-----------------
1 files changed, 1 insertions(+), 17 deletions(-)

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 30eaf14..5a1c0fb 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2096,10 +2096,6 @@ static void rcu_cleanup_after_idle(int cpu)
*/
static void rcu_prepare_for_idle(int cpu)
{
- unsigned long flags;
-
- local_irq_save(flags);
-
/*
* If there are no callbacks on this CPU, enter dyntick-idle mode.
* Also reset state to avoid prejudicing later attempts.
@@ -2107,7 +2103,6 @@ static void rcu_prepare_for_idle(int cpu)
if (!rcu_cpu_has_callbacks(cpu)) {
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
per_cpu(rcu_dyntick_drain, cpu) = 0;
- local_irq_restore(flags);
trace_rcu_prep_idle("No callbacks");
return;
}
@@ -2117,7 +2112,6 @@ static void rcu_prepare_for_idle(int cpu)
* refrained from disabling the scheduling-clock tick.
*/
if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) {
- local_irq_restore(flags);
trace_rcu_prep_idle("In holdoff");
return;
}
@@ -2142,7 +2136,6 @@ static void rcu_prepare_for_idle(int cpu)
} else if (--per_cpu(rcu_dyntick_drain, cpu) <= 0) {
/* We have hit the limit, so time to give up. */
per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
- local_irq_restore(flags);
trace_rcu_prep_idle("Begin holdoff");
invoke_rcu_core(); /* Force the CPU out of dyntick-idle. */
return;
@@ -2154,23 +2147,17 @@ static void rcu_prepare_for_idle(int cpu)
*/
#ifdef CONFIG_TREE_PREEMPT_RCU
if (per_cpu(rcu_preempt_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_preempt_qs(cpu);
force_quiescent_state(&rcu_preempt_state, 0);
- local_irq_save(flags);
}
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
if (per_cpu(rcu_sched_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_sched_qs(cpu);
force_quiescent_state(&rcu_sched_state, 0);
- local_irq_save(flags);
}
if (per_cpu(rcu_bh_data, cpu).nxtlist) {
- local_irq_restore(flags);
rcu_bh_qs(cpu);
force_quiescent_state(&rcu_bh_state, 0);
- local_irq_save(flags);
}

/*
@@ -2178,13 +2165,10 @@ static void rcu_prepare_for_idle(int cpu)
* So try forcing the callbacks through the grace period.
*/
if (rcu_cpu_has_callbacks(cpu)) {
- local_irq_restore(flags);
trace_rcu_prep_idle("More callbacks");
invoke_rcu_core();
- } else {
- local_irq_restore(flags);
+ } else
trace_rcu_prep_idle("Callbacks drained");
- }
}

#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
--
1.7.8


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