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

Lai Jiangshan
2009-04-21T03:43:25Z

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?

> + spin_lock_bh(&lock->lock);
> + preempt_enable_no_resched();
> +}
> +EXPORT_SYMBOL_GPL(xt_info_rdlock_bh);
> +

Is this OK for you:

void xt_info_rdlock_bh(void)
{
struct xt_info_lock *lock;

local_bh_disable();
lock = &__get_cpu_var(xt_info_locks);
if (likely(++lock->depth == 0))
spin_lock(&lock->lock);
}

Lai.