Re: [PATCH] netfilter: use per-cpu recursive lock (v11)

Lai Jiangshan
2009-04-21T05:37:41Z

Eric Dumazet wrote:
> Lai Jiangshan a écrit :
>> Stephen Hemminger wrote:
>>> +/**
>>> + * xt_table_info_rdlock_bh - recursive read lock for xt table info
>>> + *
>>> + * Table processing calls this to hold off any changes to table
>>> + * (on current CPU). Always leaves with bottom half disabled.
>>> + * If called recursively, then assumes bh/preempt already disabled.
>>> + */
>>> +void xt_info_rdlock_bh(void)
>>> +{
>>> + struct xt_info_lock *lock;
>>> +
>>> + preempt_disable();
>>> + lock = &__get_cpu_var(xt_info_locks);
>>> + if (likely(++lock->depth == 0))
>> Maybe I missed something. I think softirq may be still enabled here.
>> So what happen when xt_info_rdlock_bh() called recursively here?
>
> well, first time its called, you are right softirqs are enabled until
> the point we call spin_lock_bh(), right after this line :
>
>

Which context can enter the critical region?
Can irq and softirq? or softirq only?