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

From: "Paul E. McKenney" <[email-masked]>
Date: Mon, 20 Apr 2009 14:58:27 -0700

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