Date: Fri, 6 Dec 2013 22:04:41 +0100 From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> To: John-Mark Gurney <jmg@funkthat.com> Cc: Yong-Hyeon Pyun <pyunyh@gmail.com>, Jack F Vogel <jfv@freebsd.org>, Adrian Chadd <adrian@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: <956436B1-5E20-4470-B415-3311F5CC24B8@lurchi.franken.de> In-Reply-To: <20131206201748.GF55638@funkthat.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> <2D0F95A6-1321-4F8E-87FB-1B9DD33FD319@lurchi.franken.de> <20131206201748.GF55638@funkthat.com>
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On Dec 6, 2013, at 9:17 PM, John-Mark Gurney <jmg@funkthat.com> wrote: > Michael Tuexen wrote this message on Fri, Dec 06, 2013 at 21:08 +0100: >> On Dec 5, 2013, at 7:29 PM, Adrian Chadd <adrian@freebsd.org> wrote: >> >>> 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(). >>> >>> The same deal in if_em.c and igb.c >>> >>> 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=0 if we go >>> via the drbr_putback() routine, as it hasn't actually failed to >>> transmit. >>> >>> 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. >>> >>> So Michael - can you redo your patch to set err=0 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 >> =================================================================== >> --- 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 >> drbr_putback(ifp, txr->br, next); >> + err = 0; > > You probably want curly braces around this... For sure. Thanks for catching it: [bsd5:~/head/sys/dev] tuexen% svn diff -x -p Index: e1000/if_em.c =================================================================== --- e1000/if_em.c (revision 259039) +++ e1000/if_em.c (working copy) @@ -933,8 +933,10 @@ em_mq_start_locked(struct ifnet *ifp, struct tx_ri if ((err = em_xmit(txr, &next)) != 0) { if (next == NULL) drbr_advance(ifp, txr->br); - else + else { drbr_putback(ifp, txr->br, next); + err = 0; + } break; } drbr_advance(ifp, txr->br); Index: e1000/if_igb.c =================================================================== --- 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 = 0; } break; } Index: ixgbe/ixgbe.c =================================================================== --- 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 = 0; } #endif break; Index: ixgbe/ixv.c =================================================================== --- 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 = 0; } break; } Index: virtio/network/if_vtnet.c =================================================================== --- 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 = drbr_peek(ifp, br)) != NULL) { error = vtnet_txq_encap(txq, &m); if (error) { - if (m != NULL) + if (m != NULL) { drbr_putback(ifp, br, m); - else + error = 0; + } else drbr_advance(ifp, br); break; } > > -- > John-Mark Gurney Voice: +1 415 225 5579 > > "All that I will do, has been done, All that I have, has not." >
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