Messages in this thread | | | Date | Thu, 20 Aug 2009 12:02:44 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH -tip/core/rcu 3/6] Simplify RCU CPU-hotplug notification |
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Paul E. McKenney wrote: > From: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > 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> > --- > kernel/rcupdate.c | 16 +++++++++++++++- > kernel/rcupreempt.c | 25 ++----------------------- > kernel/rcutree.c | 17 +++++------------ > 3 files changed, 22 insertions(+), 36 deletions(-) > > diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c > index eae29c2..8df1156 100644 > --- a/kernel/rcupdate.c > +++ b/kernel/rcupdate.c > @@ -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);
I think, There is only one cpu in cpu online map at early boot time, it is the current cpu.
Thanks, Lai
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