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RE: [Xen-devel] Interrupt levels

To: "Nicholas Lee" <nic-lists@xxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Interrupt levels
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Thu, 10 Mar 2005 02:28:46 -0000
Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxxx>, <ian.pratt@xxxxxxxxxxxx>, <ian.pratt@xxxxxxxxxxxx>
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Thread-index: AcUlFHKsynfCJPBxQB6jBrUnUs5KmwAA4kPw
Thread-topic: [Xen-devel] Interrupt levels
 > The exact problem is 'bridge hello time' being set to zero.
> When I when I switch between '0' and '1' hello time via:
> auto internal-br
> iface internal-br inet static
>         address
>         netmask
>         network
>         broadcast
>         bridge_ports eth1
>         bridge_fd 0
>         bridge_hello 1
>         bridge_stp off

Yep, this is a problem that's cropped up several times before. I would
argue strongly that it's a bug in the bridge code to add a timer for the
current jiffies value.

On native I think you get away with is as the timer won't fire until the
next jiffie. On Xen, you'll enter Xen and then bounce straight back out
as the time has already passed.

I think we may have to hack arch xen to round to the next jiffie to
match the native behaviour.

However, the bridge's behaviour is still pretty evil -- you'll still end
up executing the code HZ (100/1000) times a second, and the intention of
the user was probably to disable execution of the code altogether. It
won't slay the machine (like executing int 200k times a second), but its
not ideal.


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