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Commit c0cfbbb0 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Paul E. McKenney
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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: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 3d3b7db0

kernel/rcutree_plugin.h

+1 −17
Original line number Diff line number Diff line
@@ -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);

	}



	/*
@@ -2178,14 +2165,11 @@ 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) */