From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Christophe Saout <christophe@saout.de>
Cc: "Xu, Dongxiao" <dongxiao.xu@intel.com>, xen-devel@lists.xensource.com
Subject: Re: new netfront and occasional receive path lockup
Date: Mon, 23 Aug 2010 17:53:13 -0700 [thread overview]
Message-ID: <4C7317F9.2060009@goop.org> (raw)
In-Reply-To: <1282502275.14390.59.camel@leto.intern.saout.de>
On 08/22/2010 11:37 AM, Christophe Saout wrote:
> Hmm, looking a bit more.
>
> rx.sring->private.netif.smartpoll_active lies in a piece of memory that
> is shared between netback and netfront, is that right?
>
> If that is so, the tx spinlock in netfront only protects against
> simultaneous modifications from another thread in netfront, so netback
> can read smartpoll_active while netfront is fiddling with it. Is that
> safe?
It depends on exactly how it is used. But any use cross-cpu shared
memory must carefully consider access ordering, and possibly have
explicit barriers to make sure that the expected ordering is actually
seen by all cpus.
J
> Note that when the lockup occurs, /proc/interrupts in the guest doesn't
> show any interrupts arriving from for eth0 anymore. Are there any
> conditions where netback waits for netfront to retrieve packages even
> when new packages arrive? (like e.g. when the ring is full and there is
> backlog into the network stack or something?) Any way to debug this from
> the Dom0 side? Like looking into the state of the ring from userspace?
> Debug options?
>
> Christophe
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>
next prev parent reply other threads:[~2010-08-24 0:53 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-22 16:43 new netfront and occasional receive path lockup Christophe Saout
2010-08-22 18:37 ` Christophe Saout
2010-08-24 0:53 ` Jeremy Fitzhardinge [this message]
2010-08-23 14:26 ` Christophe Saout
2010-08-23 16:04 ` Konrad Rzeszutek Wilk
2010-08-23 17:09 ` Christophe Saout
2010-08-24 0:46 ` Jeremy Fitzhardinge
2010-08-25 0:51 ` Xu, Dongxiao
2010-09-09 18:50 ` Pasi Kärkkäinen
2010-09-10 0:55 ` Jeremy Fitzhardinge
2010-09-10 1:45 ` Xu, Dongxiao
2010-09-10 2:25 ` Jeremy Fitzhardinge
2010-09-10 2:37 ` Xu, Dongxiao
2010-09-10 2:42 ` Jeremy Fitzhardinge
2010-09-12 1:00 ` Gerald Turner
2010-09-12 8:55 ` Jeremy Fitzhardinge
2010-09-12 17:23 ` Pasi Kärkkäinen
2010-09-12 22:40 ` Gerald Turner
2010-09-13 0:03 ` Gerald Turner
2010-09-13 0:54 ` Xu, Dongxiao
2010-09-13 2:12 ` Gerald Turner
2010-09-13 2:34 ` Xu, Dongxiao
2010-09-13 4:38 ` Gerald Turner
2010-09-13 16:01 ` Gerald Turner
2010-09-13 16:08 ` Pasi Kärkkäinen
2010-09-13 19:36 ` Jeremy Fitzhardinge
2010-09-14 8:25 ` Ian Campbell
2010-09-14 17:54 ` Jeremy Fitzhardinge
2010-09-14 18:44 ` Pasi Kärkkäinen
2010-09-15 9:46 ` Ian Campbell
2010-09-14 0:26 ` Xu, Dongxiao
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