Will Deacon <will@xxxxxxxxxx> wrote:
> > diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
> > index af22dbe85e2c..b5911985d1eb 100644
> > --- a/net/netfilter/x_tables.c
> > +++ b/net/netfilter/x_tables.c
> > @@ -1384,7 +1384,7 @@ xt_replace_table(struct xt_table *table,
> > * private.
> > */
> > smp_wmb();
> > - table->private = newinfo;
> > + WRITE_ONCE(table->private, newinfo);
>
> ... you could make this rcu_assign_pointer() and get rid of the preceding
> smp_wmb()...
Yes, it would make sense to add proper rcu annotation as well.
> > /* make sure all cpus see new ->private value */
> > smp_wmb();
>
> ... and this smp_wmb() is no longer needed because synchronize_rcu()
> takes care of the ordering.
Right, thanks.
> > @@ -1394,19 +1394,7 @@ xt_replace_table(struct xt_table *table,
> > * may still be using the old entries...
> > */
> > local_bh_enable();
> > -
> > - /* ... so wait for even xt_recseq on all cpus */
> > - for_each_possible_cpu(cpu) {
> > - seqcount_t *s = &per_cpu(xt_recseq, cpu);
> > - u32 seq = raw_read_seqcount(s);
> > -
> > - if (seq & 1) {
> > - do {
> > - cond_resched();
> > - cpu_relax();
> > - } while (seq == raw_read_seqcount(s));
> > - }
> > - }
>
> Do we still need xt_write_recseq_{begin,end}() with this removed?
Yes, it enables userspace to get stable per rule packet and byte counters.
