On Fri, Apr 24, 2009 at 08:39:26AM +0800, Lai Jiangshan wrote: > Paul E. McKenney wrote: > > On Thu, Apr 23, 2009 at 02:11:58PM +0800, Lai Jiangshan wrote: > >> Paul E. McKenney wrote: > > > > [ . . . ] > > > >> Hi, Paul > >> > >> I just typed codes in email, very like these two pathes: > >> > >> [PATCH 1/2] sched: Introduce APIs for waiting multi events > >> http://lkml.org/lkml/2009/4/14/733 > >> > >> [PATCH 2/2] rcupdate: use struct ref_completion > >> http://lkml.org/lkml/2009/4/14/734 > >> > >> Lai. > >> -------------- > > > > Interesting approach! This would get a second use for your multi-events > > waiting code above. ;-) > > > > Looks like the idea is to have the task doing the > > synchronize_rcu_bh_expedited() hold a reference across the process, > > and have each rcu_bh_fast_qs() also acquire a reference, which would > > be released in the softirq handler synchronize_rcu_bh_expedited_help(). > > > > One question -- does this approach correctly handle all the CPU hotplug > > scenarios? (I think that it might, but am not completely certain.) > > > > Thanx, Paul > > Ah, raise_softirq(RCU_EXPEDITED_SOFTIRQ) can not ensure the softirq > will be called when hotplug. > > It needs get_online_cpus() and put_online_cpus(). OK, easy fix, then. ;-) Thanx, Paul > >> #ifndef CONFIG_SMP > >> > >> static void __init synchronize_rcu_expedited_init(void) > >> { > >> } > >> > >> void synchronize_rcu_bh_expedited(void) > >> { > >> cond_resched(); > >> } > >> > >> #else /* #ifndef CONFIG_SMP */ > >> > >> static DEFINE_MUTEX(synchronize_rcu_bh_mutex); > >> static DEFINE_PER_CPU(int, call_only_once); /* is it need ? */ > >> static struct ref_completion rcu_bh_expedited_completion > >> > >> static void synchronize_rcu_bh_expedited_help(struct softirq_action *unused) > >> { > >> if (__get_cpu_var(call_only_once)) { > >> smp_mb(); > >> ref_completion_put(&rcu_bh_expedited_completion); > >> __get_cpu_var(call_only_once) = 0; > >> } > >> } > >> > >> static void rcu_bh_fast_qs(void *unused) > >> { > >> __get_cpu_var(call_only_once) = 1; > >> ref_completion_get(&rcu_bh_expedited_completion); > >> raise_softirq(RCU_EXPEDITED_SOFTIRQ); > >> } > >> > >> static void __init synchronize_rcu_expedited_init(void) > >> { > >> open_softirq(RCU_EXPEDITED_SOFTIRQ, synchronize_rcu_bh_expedited_help); > >> } > >> > >> void synchronize_rcu_bh_expedited(void) > >> { > >> mutex_lock(&synchronize_rcu_bh_mutex); > >> > >> ref_completion_get_init(&rcu_bh_expedited_completion); > >> > >> smp_call_function(rcu_bh_fast_qs, NULL, 1); > >> > >> ref_completion_put_init(&rcu_bh_expedited_completion); > >> ref_completion_wait(&rcu_bh_expedited_completion); > >> > >> mutex_unlock(&synchronize_rcu_bh_mutex); > >> } > >> > >> #endif /* #else #ifndef CONFIG_SMP */ > >> > > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
