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Re: [Xen-devel] [PATCH 1 of 3] fix S3 suspend error

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Lu, Guanqun" <guanqun.lu@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 1 of 3] fix S3 suspend error
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 23 Feb 2009 05:15:09 -0800
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On 23/02/2009 04:46, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> I can't ensure my understanding exactly matching latest Linux
> S3 implementation which evolves quickly. But generally device
> drivers typically are allowed with two callbacks, one being invoked
> with irq enabled and the other with irq disabled, since some actions
> have such requirement. On the other side, system device class,
> such as ioapic, lapic, etc. are saved with irq disabled after other
> external devices.
> 
> Xen owns a few devices with most as system class, so for
> simplicity interrupt is disabled from start. It's not worthy of touching
> this flow for this simple spinlock issue, imo. :-)

Can you point out any core devices in modern Linux 2.6 which implement the
suspend_late() or *_noirq() callbacks (those appear to be the ones handled
in device_power_down() with IRQs disabled)? They seem very obsolete/legacy,
and looks to me like we could unconditionally *not* disable IRQs rather than
unconditionally disabling them.

 -- Keir



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