Messages in this thread | | | Date | Wed, 19 Aug 2009 21:21:24 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH -tip/core/rcu 3/6] Simplify RCU CPU-hotplug notification |
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On Thu, Aug 20, 2009 at 12:02:44PM +0800, Lai Jiangshan wrote: > 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.
Indeed there is. But I wouldn't put it past the fast-boot guys to parallelize early boot. ;-)
Thanx, Paul
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