On Fri, Jul 11, 2003 at 01:58:49AM -0700, Ned Ren wrote:
> Hi, 
> 
> This maybe a silly question. I'm wondering for hook modules that I
> write for netfilter, is it necessary to do locking (critical section)
> when accessing my own global structures? 

Yes, it is always necessarry to lock your global structures.  All of
netfilter is running in softirq context.

> This is regarding SINGLE CPU systems, is there anything that would
> preempt my module while it's at it such as interrupt etc?

hard interrupts can always interrupt a softirq - but a softirq doesn't
interrupt another softirq (on single cpu).

However, all kernel code _has_ to be SMP safe.

> Thank you!

-- 
- Harald Welte <laforge@netfilter.org>             http://www.netfilter.org/
============================================================================
  "Fragmentation is like classful addressing -- an interesting early
   architectural error that shows how much experimentation was going
   on while IP was being designed."                    -- Paul Vixie