Date: Fri, 6 Dec 2013 21:08:13 +0100 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: Adrian Chadd <adrian@freebsd.org> Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>, Jack F Vogel <jfv@freebsd.org>, "freebsd-net@freebsd.org list" <freebsd-net@freebsd.org> Subject: Re: A small fix for if_em.c, if_igb.c, if_ixgbe.c Message-ID: <2D0F95A6-1321-4F8E-87FB-1B9DD33FD319@lurchi.franken.de> In-Reply-To: <CAJ-Vmo=kfoPMYjZ0WAtqmoJMz1utXH50SW9N92RA83EMUzY7WA@mail.gmail.com> References: <521B9C2A-EECC-4412-9F68-2235320EF324@lurchi.franken.de> <20131202022338.GA3500@michelle.cdnetworks.com> <B9593E83-E687-49E9-ABDC-B2DD615180E9@lurchi.franken.de> <20131203021658.GC2981@michelle.cdnetworks.com> <CAJ-Vmo=kfoPMYjZ0WAtqmoJMz1utXH50SW9N92RA83EMUzY7WA@mail.gmail.com>
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On Dec 5, 2013, at 7:29 PM, Adrian Chadd <adrian@freebsd.org> wrote: > Hi, >=20 > Yes. Looking at the ixgbe code, ixgbe_mq_start_locked() returns an > error from ixgbe_xmit() but if it fails, it puts the buffer back. But > it's already successfully queued a frame to the driver, so in this > instance it shouldn't return the error from ixgbe_mq_start_locked(). >=20 > The same deal in if_em.c and igb.c >=20 > Now, drbr_putback() used to fail and now it doesn't, as you've said. > So we should change the xxx_mq_start_locked() to set err=3D0 if we go > via the drbr_putback() routine, as it hasn't actually failed to > transmit. >=20 > Now the very dirty thing is this - the error from xxx_transmit() is > for the mbuf being queued at the end; but xxx_mq_start_locked() > failures are for transmitting from the front. If there's only packet > in the queue and that fails then they're the same thing and returning > the error from xxx_mq_start_locked() matches the current mbuf being > queued. But otherwise, they're referring to totally different packets. > For TCP this may hurt; the TCP stack treats ENOBUFS a certain way and > kicks off a timer to schedule a retransmit. I don't think we can fix > _this_ right now. >=20 > So Michael - can you redo your patch to set err=3D0 if drbr_putback() = is > called, and retest? Hi Adrian, I guess you are talking about a patch like: [bsd5:~/head/sys/dev] tuexen% svn diff -x -p Index: e1000/if_em.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 --- e1000/if_em.c (revision 259039) +++ e1000/if_em.c (working copy) @@ -935,6 +935,7 @@ em_mq_start_locked(struct ifnet *ifp, struct tx_ri drbr_advance(ifp, txr->br); else=20 drbr_putback(ifp, txr->br, next); + err =3D 0; break; } drbr_advance(ifp, txr->br); Index: e1000/if_igb.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 --- e1000/if_igb.c (revision 259039) +++ e1000/if_igb.c (working copy) @@ -1024,6 +1024,7 @@ igb_mq_start_locked(struct ifnet *ifp, struct tx_r * may have changed it. */ drbr_putback(ifp, txr->br, next); + err =3D 0; } break; } Index: ixgbe/ixgbe.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 --- ixgbe/ixgbe.c (revision 259039) +++ ixgbe/ixgbe.c (working copy) @@ -864,6 +864,7 @@ ixgbe_mq_start_locked(struct ifnet *ifp, struct tx drbr_advance(ifp, txr->br); } else { drbr_putback(ifp, txr->br, next); + err =3D 0; } #endif break; Index: ixgbe/ixv.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 --- ixgbe/ixv.c (revision 259039) +++ ixgbe/ixv.c (working copy) @@ -629,6 +629,7 @@ ixv_mq_start_locked(struct ifnet *ifp, struct tx_r drbr_advance(ifp, txr->br); } else { drbr_putback(ifp, txr->br, next); + err =3D 0; } break; } Index: virtio/network/if_vtnet.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 --- virtio/network/if_vtnet.c (revision 259039) +++ virtio/network/if_vtnet.c (working copy) @@ -2242,9 +2242,10 @@ vtnet_txq_mq_start_locked(struct vtnet_txq *txq, = s while ((m =3D drbr_peek(ifp, br)) !=3D NULL) { error =3D vtnet_txq_encap(txq, &m); if (error) { - if (m !=3D NULL) + if (m !=3D NULL) { drbr_putback(ifp, br, m); - else + error =3D 0; + } else drbr_advance(ifp, br); break; } I looked for drivers using drbr_putback() and used a similar fix. Please = note that sys/dev/oce/oce_if.c seems strange. It uses drbr_putback() and = drbr_enqueue(), so I left it out for now. I tested the igb driver and the above patch fixes the problem I saw. =46rom your above description I think the above patch is a valid patch. However, xxx_transmit() can still return an error, even if there is no problem with the provided packet. This is an issue for transport = protocols... Best regards Michael >=20 > Thanks! >=20 >=20 >=20 >=20 > -adrian >=20
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