Re: 2.6.9-rc3-mm2

[Rusty Russell <rusty@rustcorp.com.au>]

On Wed, 2004-10-06 at 00:07, Dominik Karall wrote:
> On Monday 04 October 2004 11:02, Andrew Morton wrote:
> > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.9-rc3/2.6
> >.9-rc3-mm2/
> 
> some more scheduling/preempt problems. following patches were applied:
> --- 
> 25/include/linux/netfilter_ipv4/ip_conntrack.h~conntrack-preempt-safety-fix 
> Mon Oct  4 14:36:19 2004
> +++ 25-akpm/include/linux/netfilter_ipv4/ip_conntrack.h Mon Oct  4 14:37:02 
> 2004
> @@ -311,10 +311,11 @@ struct ip_conntrack_stat
>         unsigned int expect_delete;
>  };
>  
> -#define CONNTRACK_STAT_INC(count)                              \
> -       do {                                                    \
> -               per_cpu(ip_conntrack_stat, get_cpu()).count++;  \
> -               put_cpu();                                      \
> +#define CONNTRACK_STAT_INC(count)                                      \
> +       do {                                                            \
> +               preempt_disable();                                      \
> +               per_cpu(ip_conntrack_stat, smp_processor_id()).count++; \
> +               preempt_disable();                                      \
>         } while (0)

Please, please please!  Never use per_cpu(XXX, smp_processor_id())!  In
this case, it's "get_cpu_var(ip_conntrack_stat).count++; put_cpu(),
although I think this code should only be called in a softirq, so a
simple "__get_cpu_var(ip_conntrack_stat).count++;" is sufficient.

Rusty.
-- 
Anyone who quotes me in their signature is an idiot -- Rusty Russell