Date: Fri, 6 Dec 2013 12:17:48 -0800 From: John-Mark Gurney <jmg@funkthat.com> To: Michael Tuexen <Michael.Tuexen@lurchi.franken.de> 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: <20131206201748.GF55638@funkthat.com> In-Reply-To: <2D0F95A6-1321-4F8E-87FB-1B9DD33FD319@lurchi.franken.de> 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>
next in thread | previous in thread | raw e-mail | index | archive | help
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...
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20131206201748.GF55638>