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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: Paul 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: Ingo Molnar <mingo@elte.hu>
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parent
799e64f05f
commit
2e59755808
3 changed files with 22 additions and 36 deletions
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@ -217,9 +217,13 @@ static void rcu_migrate_callback(struct rcu_head *notused)
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wake_up(&rcu_migrate_wq);
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}
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extern int rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu);
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static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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rcu_cpu_notify(self, action, hcpu);
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if (action == CPU_DYING) {
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/*
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* preempt_disable() in on_each_cpu() prevents stop_machine(),
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@ -244,8 +248,18 @@ static int __cpuinit rcu_barrier_cpu_hotplug(struct notifier_block *self,
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void __init rcu_init(void)
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{
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int i;
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__rcu_init();
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hotcpu_notifier(rcu_barrier_cpu_hotplug, 0);
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cpu_notifier(rcu_barrier_cpu_hotplug, 0);
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/*
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* We don't need protection against CPU-hotplug here because
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* this is called early in boot, before either interrupts
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* or the scheduler are operational.
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*/
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for_each_online_cpu(i)
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rcu_barrier_cpu_hotplug(NULL, CPU_UP_PREPARE, (void *)(long)i);
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}
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void rcu_scheduler_starting(void)
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@ -1417,8 +1417,8 @@ int rcu_pending(int cpu)
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return 0;
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}
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static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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long cpu = (long)hcpu;
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@ -1439,10 +1439,6 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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return NOTIFY_OK;
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}
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static struct notifier_block __cpuinitdata rcu_nb = {
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.notifier_call = rcu_cpu_notify,
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};
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void __init __rcu_init(void)
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{
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int cpu;
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@ -1471,23 +1467,6 @@ void __init __rcu_init(void)
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rdp->waitschedtail = &rdp->waitschedlist;
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rdp->rcu_sched_sleeping = 0;
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}
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register_cpu_notifier(&rcu_nb);
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/*
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* We don't need protection against CPU-Hotplug here
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* since
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* a) If a CPU comes online while we are iterating over the
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* cpu_online_mask below, we would only end up making a
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* duplicate call to rcu_online_cpu() which sets the corresponding
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* CPU's mask in the rcu_cpu_online_map.
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*
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* b) A CPU cannot go offline at this point in time since the user
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* does not have access to the sysfs interface, nor do we
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* suspend the system.
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*/
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for_each_online_cpu(cpu)
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rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long) cpu);
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open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
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}
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@ -1132,6 +1132,8 @@ __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
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{
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unsigned long flags;
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WARN_ON_ONCE(rdp->beenonline == 0);
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/*
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* If an RCU GP has gone long enough, go check for dyntick
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* idle CPUs and, if needed, send resched IPIs.
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@ -1416,14 +1418,13 @@ static void __cpuinit rcu_online_cpu(int cpu)
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{
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rcu_init_percpu_data(cpu, &rcu_state);
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rcu_init_percpu_data(cpu, &rcu_bh_state);
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open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
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}
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/*
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* Handle CPU online/offline notifcation events.
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*/
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static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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int __cpuinit rcu_cpu_notify(struct notifier_block *self,
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unsigned long action, void *hcpu)
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{
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long cpu = (long)hcpu;
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@ -1532,10 +1533,6 @@ do { \
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} \
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} while (0)
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static struct notifier_block __cpuinitdata rcu_nb = {
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.notifier_call = rcu_cpu_notify,
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};
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void __init __rcu_init(void)
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{
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int i; /* All used by RCU_DATA_PTR_INIT(). */
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@ -1554,11 +1551,7 @@ void __init __rcu_init(void)
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RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);
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for_each_possible_cpu(i)
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rcu_boot_init_percpu_data(i, &rcu_bh_state);
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for_each_online_cpu(i)
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rcu_cpu_notify(&rcu_nb, CPU_UP_PREPARE, (void *)(long)i);
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/* Register notifier for non-boot CPUs */
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register_cpu_notifier(&rcu_nb);
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open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
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}
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module_param(blimit, int, 0);
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