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Re: [Xen-devel] [PATCH] Re-enable MSI support

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, Espen Skoglund <espen.skoglund@xxxxxxxxxxxxx>, "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Re-enable MSI support
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 10 Dec 2008 15:36:38 +0000
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On 10/12/2008 15:24, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

>> Except, since it is used as a read_lock most of the time it does not
>> actually protect things in the way a spinlock would do.
> 
> Ahh, yes, I didn't realize this. So how do you think changing it to spinlock,
> since it is not performance ciritical. Or do you know how much benifit for
> read_lock?

A spinlock is actually faster unless the read sections are frequently
contended, in which case the lost parallelism counteracts the faster lock.

 -- Keir

> Also, as for the reference to pci_dev, do you have plan to add such support?
> For example, I'm not sure if we can return fail for pci_remove_device if there
> is still reference to it? Will dom0 support such failure?



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