Re: [PATCH] netfilter: use per-cpu recursive lock (v10)

Paul E. McKenney
2009-04-20T21:58:46Z

On Tue, Apr 21, 2009 at 07:23:31AM +1000, Paul Mackerras wrote:
> Eric Dumazet writes:
>
> > OK, but we still have a problem on machines with >= 250 cpus,
> > because calling 250 times spin_lock() is going to overflow preempt_count,
> > as each spin_lock() increases preempt_count by one.
>
> Huh? Each cpu has its own separate preempt_count.

But a single CPU is acquiring one lock per CPU, so all the increments
are to one CPU's preempt_count. :-(

Thanx, Paul