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Commit 2e597558 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
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rcu: Simplify RCU CPU-hotplug notification 



Use the new cpu_notifier() API to simplify RCU's CPU-hotplug
notifiers, collapsing down to a single such notifier.

This makes it trivial to provide the notifier-ordering
guarantee that rcu_barrier() depends on.

Also remove redundant open_softirq() calls from Hierarchical
RCU notifier.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: josht@linux.vnet.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: hugh.dickins@tiscali.co.uk
Cc: benh@kernel.crashing.org
LKML-Reference: <12503552312510-git-send-email->
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 799e64f0

kernel/rcupdate.c

+15 −1
Original line number Diff line number Diff line
@@ -217,9 +217,13 @@ static void rcu_migrate_callback(struct rcu_head *notused) 
		wake_up(&rcu_migrate_wq);

}



extern int rcu_cpu_notify(struct notifier_block *self,

			  unsigned long action, void *hcpu);



static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,

		unsigned long action, void *hcpu)

{

	rcu_cpu_notify(self, action, hcpu);

	if (action == CPU_DYING) {

		/*

		 * preempt_disable() in on_each_cpu() prevents stop_machine(),
@@ -244,8 +248,18 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self, 


void __init rcu_init(void)

{

	int i;



	__rcu_init();

	hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);

	cpu_notifier(rcu_barrier_cpu_hotplug, 0);



	/*

	 * We don't need protection against CPU-hotplug here because

	 * this is called early in boot, before either interrupts

	 * or the scheduler are operational.

	 */

	for_each_online_cpu(i)

		rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);

}



void rcu_scheduler_starting(void)

kernel/rcupreempt.c

+2 −23
Original line number Diff line number Diff line
@@ -1417,7 +1417,7 @@ int rcu_pending(int cpu) 
	return 0;

}



static int __cpuinit rcu_cpu_notify(struct notifier_block *self,

int __cpuinit rcu_cpu_notify(struct notifier_block *self,

			     unsigned long action, void *hcpu)

{

	long cpu = (long)hcpu;
@@ -1439,10 +1439,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, 
	return NOTIFY_OK;

}



static struct notifier_block __cpuinitdata rcu_nb = {

	.notifier_call = rcu_cpu_notify,

};



void __init __rcu_init(void)

{

	int cpu;
@@ -1471,23 +1467,6 @@ void __init __rcu_init(void) 
		rdp->waitschedtail = &rdp->waitschedlist;

		rdp->rcu_sched_sleeping = 0;

	}

	register_cpu_notifier(&rcu_nb);



	/*

	 * We don't need protection against CPU-Hotplug here

	 * since

	 * a) If a CPU comes online while we are iterating over the

	 *    cpu_online_mask below, we would only end up making a

	 *    duplicate call to rcu_online_cpu() which sets the corresponding

	 *    CPU's mask in the rcu_cpu_online_map.

	 *

	 * b) A CPU cannot go offline at this point in time since the user

	 *    does not have access to the sysfs interface, nor do we

	 *    suspend the system.

	 */

	for_each_online_cpu(cpu)

		rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE,	(void *)(long) cpu);



	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);

}

kernel/rcutree.c

+5 −12
Original line number Diff line number Diff line
@@ -1132,6 +1132,8 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) 
{

	unsigned long flags;



	WARN_ON_ONCE(rdp->beenonline == 0);



	/*

	 * If an RCU GP has gone long enough, go check for dyntick

	 * idle CPUs and, if needed, send resched IPIs.
@@ -1416,13 +1418,12 @@ static void __cpuinit rcu_online_cpu(int cpu) 
{

	rcu_init_percpu_data(cpu, &rcu_state);

	rcu_init_percpu_data(cpu, &rcu_bh_state);

	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);

}



/*

 * Handle CPU online/offline notifcation events.

 */

static int __cpuinit rcu_cpu_notify(struct notifier_block *self,

int __cpuinit rcu_cpu_notify(struct notifier_block *self,

			     unsigned long action, void *hcpu)

{

	long cpu = (long)hcpu;
@@ -1532,10 +1533,6 @@ do { \ 
	} \

} while (0)



static struct notifier_block __cpuinitdata rcu_nb = {

	.notifier_call	= rcu_cpu_notify,

};



void __init __rcu_init(void)

{

	int i;			/* All used by RCU_DATA_PTR_INIT(). */
@@ -1554,11 +1551,7 @@ void __init __rcu_init(void) 
	RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);

	for_each_possible_cpu(i)

		rcu_boot_init_percpu_data(i, &rcu_bh_state);



	for_each_online_cpu(i)

		rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);

	/* Register notifier for non-boot CPUs */

	register_cpu_notifier(&rcu_nb);

	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);

}



module_param(blimit, int, 0);