Date: Thu, 8 Apr 2004 22:36:18 +0300 From: Ruslan Ermilov <ru@FreeBSD.org> To: Bruce Evans <bde@zeta.org.au> Cc: net@FreeBSD.org Subject: Re: sk ethernet driver: watchdog timeout Message-ID: <20040408193618.GA1919@ip.net.ua> In-Reply-To: <20040407235838.K11719@gamplex.bde.org> References: <20240000.1079394807@palle.girgensohn.se> <wpy8q04buf.fsf@heho.snv.jussieu.fr> <3810000.1081299464@palle.girgensohn.se> <20040407235838.K11719@gamplex.bde.org>
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On Thu, Apr 08, 2004 at 12:17:06AM +1000, Bruce Evans wrote:
[...]
> The following patch reduces the problem on A7V8X-E a little. It limits
> the tx queue to 1 packet and fixes handling of the timeout on txeof.
> The first part probably makes the second part a no-op. Without this,
> my A7V8X-E hangs on even light nfs activity (e.g., copying a 1MB file
> to nfs). With it, it takes heavier nfs activity to hang (makeworld
> never completes, and a flood ping always hangs).
>=20
> I first suspected an interrupt-related bug, but the bug seems to be
> more hardware-specific. Examination of the output queues shows that
> the tx sometimes just stops before processing all packets. Resetting
> in sk_watchdog() doesn't always fix the problem, and the timeout usually
> stops firing after a couple of unsuccessful resets, giving a completely
> hung device. But the problem may be related to interrupt timing, since
> it is much smaller under RELENG_4. RELENG_4 hangs about as often
> without this hack as -current does with it.
>=20
> nv0 hangs similarly. fxp0 just works.
>=20
> %%%
> Index: if_sk.c
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> RCS file: /home/ncvs/src/sys/pci/if_sk.c,v
> retrieving revision 1.78
> diff -u -2 -r1.78 if_sk.c
> --- if_sk.c 31 Mar 2004 12:35:51 -0000 1.78
> +++ if_sk.c 1 Apr 2004 07:33:58 -0000
> @@ -1830,4 +1830,9 @@
> SK_IF_LOCK(sc_if);
>=20
> + if (sc_if->sk_cdata.sk_tx_cnt > 0) {
> + SK_IF_UNLOCK(sc_if);
> + return;
> + }
> +
> idx =3D sc_if->sk_cdata.sk_tx_prod;
>=20
> @@ -1853,4 +1858,5 @@
> */
> BPF_MTAP(ifp, m_head);
> + break;
> }
>=20
> @@ -2000,5 +2031,4 @@
> sc_if->sk_cdata.sk_tx_cnt--;
> SK_INC(idx, SK_TX_RING_CNT);
> - ifp->if_timer =3D 0;
> }
>=20
> @@ -2007,4 +2037,6 @@
> if (cur_tx !=3D NULL)
> ifp->if_flags &=3D ~IFF_OACTIVE;
> +
> + ifp->if_timer =3D (sc_if->sk_cdata.sk_tx_cnt =3D=3D 0) ? 0 : 5;
>=20
> return;
> %%%
>=20
Always recharging the timer to 5 when there's some TX work still
left is a bug. With DEVICE_POLLING (yes, I have plans to add
polling(4) support for sk(4) too), sk_txeof() will be called
periodically, and if the card gets stuck, the if_timer will
never downgrade to zero, and sk_watchdog() will never be called.
Without DEVICE_POLLING, recharging it back to 5 even when
if_timer reaches 0 is still pointless, because when if_timer is
0 while in the sk_txeof(), it means it's called by sk_watchdog()
which will reinit the card and both RX and TX lists, making them
empty, so having the if_timer with the value of 5 _after_
executing the watchdog cleaning and having _no_ TX activity at
all may cause a second (false) watchdog. My version of the
TX fixes (which also fixes resetting of IFF_OACTIVE):
%%%
Index: if_sk.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
RCS file: /home/ncvs/src/sys/pci/if_sk.c,v
retrieving revision 1.78
diff -u -p -r1.78 if_sk.c
--- if_sk.c 31 Mar 2004 12:35:51 -0000 1.78
+++ if_sk.c 8 Apr 2004 19:10:50 -0000
@@ -1998,14 +1998,14 @@ sk_txeof(sc_if)
sc_if->sk_cdata.sk_tx_chain[idx].sk_mbuf =3D NULL;
}
sc_if->sk_cdata.sk_tx_cnt--;
+ ifp->if_flags &=3D ~IFF_OACTIVE;
SK_INC(idx, SK_TX_RING_CNT);
- ifp->if_timer =3D 0;
}
=20
sc_if->sk_cdata.sk_tx_cons =3D idx;
=20
- if (cur_tx !=3D NULL)
- ifp->if_flags &=3D ~IFF_OACTIVE;
+ if (sc_if->sk_cdata.sk_tx_cnt =3D=3D 0)
+ ifp->if_timer =3D 0;
=20
return;
}
%%%
We have been running the 3COM 3C940 card on 4.9 (and from today
on 4.10-BETA) without any problems and under a heavy TX load.
Cheers,
--=20
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer
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