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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>
hifive-unleashed-5.1
Paul E. McKenney 2009-08-15 09:53:48 -07:00 committed by Ingo Molnar
parent 799e64f05f
commit 2e59755808
3 changed files with 22 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
kernel/rcupdate.c
View File

@ -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)

25
kernel/rcupreempt.c
View File

@ -1417,8 +1417,8 @@ int rcu_pending(int cpu)
return 0;
}
static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
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);
}

17
kernel/rcutree.c
View File

@ -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.
@ -1416,14 +1418,13 @@ 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,
unsigned long action, void *hcpu)
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);