On Fri, Oct 23, 2015 at 02:41:34PM +0200, Martin Pieuchot wrote:
> On 22/10/15(Thu) 19:42, Martin Pieuchot wrote:
> > Now that we have a single refcounting mechanism for route entries, I'd
> > like to use atomic operations and grab the KERNEL_LOCK only if a CPU is
> > dropping the last reference on an entry.
> >
> > Currently this only matters for MPLS. I intentionally use atomic_* ops
> > because I'd like to see be able to see if a counter goes negative.
> >
> > For symmetry reasons I'm also moving the KERNEL_LOCK() inside rtalloc().
> > These two functions are my current targets.
> >
> > Comments, oks?
>
> Updated diff after some comments from dlg@ and bluhm@.
OK bluhm@
>
> Index: net/route.c
> ===================================================================
> RCS file: /cvs/src/sys/net/route.c,v
> retrieving revision 1.258
> diff -u -p -r1.258 route.c
> --- net/route.c 22 Oct 2015 17:19:38 -0000 1.258
> +++ net/route.c 23 Oct 2015 12:38:58 -0000
> @@ -215,6 +215,7 @@ rtalloc(struct sockaddr *dst, int flags,
> info.rti_info[RTAX_DST] = dst;
>
> s = splsoftnet();
> + KERNEL_LOCK();
> rt = rtable_match(tableid, dst);
> if (rt != NULL) {
> if ((rt->rt_flags & RTF_CLONING) && ISSET(flags, RT_RESOLVE)) {
> @@ -236,6 +237,7 @@ miss:
> if (ISSET(flags, RT_REPORT))
> rt_missmsg(RTM_MISS, &info, 0, NULL, error, tableid);
> }
> + KERNEL_UNLOCK();
> splx(s);
> return (rt);
> }
> @@ -337,25 +339,29 @@ rtalloc_mpath(struct sockaddr *dst, uint
> void
> rtref(struct rtentry *rt)
> {
> - rt->rt_refcnt++;
> + atomic_inc_int(&rt->rt_refcnt);
> }
>
> void
> rtfree(struct rtentry *rt)
> {
> struct ifaddr *ifa;
> + int refcnt;
>
> if (rt == NULL)
> return;
>
> - if (--rt->rt_refcnt <= 0) {
> + refcnt = (int)atomic_dec_int_nv(&rt->rt_refcnt);
> + if (refcnt <= 0) {
> KASSERT(!ISSET(rt->rt_flags, RTF_UP));
> KASSERT(!RT_ROOT(rt));
> - rttrash--;
> - if (rt->rt_refcnt < 0) {
> + atomic_dec_int(&rttrash);
> + if (refcnt < 0) {
> printf("rtfree: %p not freed (neg refs)\n", rt);
> return;
> }
> +
> + KERNEL_LOCK();
> rt_timer_remove_all(rt);
> ifa = rt->rt_ifa;
> if (ifa)
> @@ -368,6 +374,8 @@ rtfree(struct rtentry *rt)
> if (rt->rt_gateway)
> free(rt->rt_gateway, M_RTABLE, 0);
> free(rt_key(rt), M_RTABLE, 0);
> + KERNEL_UNLOCK();
> +
> pool_put(&rtentry_pool, rt);
> }
> }
> @@ -773,7 +781,7 @@ rtrequest1(int req, struct rt_addrinfo *
> rt->rt_flags &= ~RTF_UP;
> if ((ifa = rt->rt_ifa) && ifa->ifa_rtrequest)
> ifa->ifa_rtrequest(RTM_DELETE, rt);
> - rttrash++;
> + atomic_inc_int(&rttrash);
>
> if (ret_nrt != NULL)
> *ret_nrt = rt;
