rcu: No interrupt disabling for rcu_prepare_for_idle()

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>

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 98ce17c..5e25ee3 100644 (file)
--- 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) */