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(). > >> #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
