On Wed, 2015-09-02 at 16:10 -0700, Martin KaFai Lau wrote:
> On Wed, Sep 02, 2015 at 03:48:57PM -0700, Eric Dumazet wrote:
> > On Wed, 2015-09-02 at 14:52 -0700, Martin KaFai Lau wrote:
> > > On Wed, Sep 02, 2015 at 02:30:45PM -0700, Eric Dumazet wrote:
> > > > Object cannot be freed until all cpus have exited their RCU sections.
> > > You meant the dst_destroy() here will wait for all cpus exited their RCU
> > > sections?
> > >
> > > static inline void dst_free(struct dst_entry *dst)
> > > {
> > > if (dst->obsolete > 0)
> > > return;
> > > if (!atomic_read(&dst->__refcnt)) {
> > > dst = dst_destroy(dst);
> > > if (!dst)
> > > return;
> > > }
> > > __dst_free(dst);
> > > }
> >
> > dst_free() is called after RCU grace period, in the case you are
> > interested in.
> >
> > Look at dst_rcu_free() and rt_free()
> Yes for IPv4 FIB
>
> Not for IPv6 FIB. F.e. rt6_release()
> The IPv6 FIB is protected by rwlock now.
Oh well. I gave you a hint. I was not saying that it was currently used
in IPv6.
Are you telling me that IPv6 needs to continue to use techniques from
1990 ?
Surely we can use modern stuff, like proper RCU and/or seqlocks.
Since you are fixing a day-0 bug, I do not believe there is a particular
hurry to be conservative.
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