Date: Fri, 9 Nov 2012 17:51:49 +0100 From: Fabien Thomas <fabien.thomas@netasq.com> To: Ingo Flaschberger <if@xip.at> Cc: freebsd-net@freebsd.org Subject: Re: [patch] reducing arp locking Message-ID: <AA0D6054-D300-409E-918C-98B206D11F55@netasq.com> In-Reply-To: <509D32CC.6000201@xip.at> References: <509AEDAC.10002@FreeBSD.org> <509B884F.7040106@networx.ch> <509B88B1.3070905@FreeBSD.org> <49EE4F42-6162-40F4-9DE0-1ACA1289B225@netasq.com> <509CC776.9010200@FreeBSD.org> <37E1F76F-D951-4B36-AF00-039DA1CC5CF3@netasq.com> <509CE6A2.2040200@FreeBSD.org> <8169CD67-E444-46FC-A7C8-DD6FB59091E1@netasq.com> <509D32CC.6000201@xip.at>
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Le 9 nov. 2012 =E0 17:43, Ingo Flaschberger a =E9crit :
> Am 09.11.2012 15:03, schrieb Fabien Thomas:
>> In in_arpinput only exclusive access to the entry is taken during the =
update no IF_AFDATA_LOCK that's why i was surprised.
>=20
> what about this:
I'm not against optimizing but an API that seems clear (correct this if =
i'm wrong):
- one lock for list modification
- one RW lock for lle entry access
- one refcount for ptr unref
is now a lot more unclear and from my point of view dangerous.
My next question is why do we need a per entry lock if we use the table =
lock to protect entry access?
Fabien
=20
> --
> --- /usr/src/sys/netinet/if_ether.c_org 2012-11-09 16:15:43.000000000 =
+0000
> +++ /usr/src/sys/netinet/if_ether.c 2012-11-09 16:16:37.000000000 =
+0000
> @@ -685,7 +685,7 @@
> flags |=3D LLE_EXCLUSIVE;
> IF_AFDATA_LOCK(ifp);
> la =3D lla_lookup(LLTABLE(ifp), flags, (struct sockaddr =
*)&sin);
> - IF_AFDATA_UNLOCK(ifp);
> +
> if (la !=3D NULL) {
> /* the following is not an error when doing bridging */
> if (!bridged && la->lle_tbl->llt_ifp !=3D ifp && =
!carp_match) {
> @@ -697,12 +697,14 @@
> ifp->if_addrlen, (u_char =
*)ar_sha(ah), ":",
> ifp->if_xname);
> LLE_WUNLOCK(la);
> + IF_AFDATA_UNLOCK(ifp);
> goto reply;
> }
> if ((la->la_flags & LLE_VALID) &&
> bcmp(ar_sha(ah), &la->ll_addr, ifp->if_addrlen)) {
> if (la->la_flags & LLE_STATIC) {
> LLE_WUNLOCK(la);
> + IF_AFDATA_UNLOCK(ifp);
> if (log_arp_permanent_modify)
> log(LOG_ERR,
> "arp: %*D attempts to =
modify "
> @@ -725,6 +727,7 @@
>=20
> if (ifp->if_addrlen !=3D ah->ar_hln) {
> LLE_WUNLOCK(la);
> + IF_AFDATA_UNLOCK(ifp);
> log(LOG_WARNING, "arp from %*D: addr len: new =
%d, "
> "i/f %d (ignored)\n", ifp->if_addrlen,
> (u_char *) ar_sha(ah), ":", ah->ar_hln,
> @@ -763,14 +766,19 @@
> la->la_numheld =3D 0;
> memcpy(&sa, L3_ADDR(la), sizeof(sa));
> LLE_WUNLOCK(la);
> + IF_AFDATA_UNLOCK(ifp);
> for (; m_hold !=3D NULL; m_hold =3D =
m_hold_next) {
> m_hold_next =3D m_hold->m_nextpkt;
> m_hold->m_nextpkt =3D NULL;
> (*ifp->if_output)(ifp, m_hold, &sa, =
NULL);
> }
> - } else
> + } else {
> LLE_WUNLOCK(la);
> - }
> + IF_AFDATA_UNLOCK(ifp);
> + }
> + } else {
> + IF_AFDATA_UNLOCK(ifp);
> + }
> reply:
> if (op !=3D ARPOP_REQUEST)
> goto drop;
> --
>=20
> Kind regards,
> Ingo Flaschberger
>=20
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