netdev - Re: smp_affinity, MSI-X and 2.6.21.1

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Message-ID: <p733b26waha.fsf@bingen.suse.de>
Date:	09 May 2007 12:35:29 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Rick Jones <rick.jones2@...com>
Cc:	Linux Network Development list <netdev@...r.kernel.org>
Subject: Re: smp_affinity, MSI-X and 2.6.21.1

Rick Jones <rick.jones2@...com> writes:

> Folks -
> 
> Is it a bug, or a feature that after changing a device's smp_affinity
> via echo "N" >> /proc/irq/M/smp_affinity that the new mask isn't
> visible via cat /proc/irq/M/smp_affinity until after actual interrupts
> are taken?

Intel chipsets can only safely update affinity during interrupt processing.
You see a side effect of the code implementing this restriction.

-Andi
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