From mboxrd@z Thu Jan  1 00:00:00 1970
From: George Dunlap <George.Dunlap@eu.citrix.com>
Subject: Re: Can Xen sleep or wake up a thread?
Date: Wed, 9 Oct 2013 12:15:58 +0100
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To: Xinxin Jin <xinxinjin89@gmail.com>
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On Tue, Oct 8, 2013 at 4:11 PM, Xinxin Jin <xinxinjin89@gmail.com> wrote:
> Hi everyone,
>
> I found in Xen, when synchronization between multiple threads is needed, Xen
> always uses busy wait or simple spin lock. In linux, the kernel can block a
> waiting thread and schedule other threads for execution. Why does Xen do not
> have this mechanism? I guess it is because the performance issue? A lot of
> appreciation for your answer !!

Linux keeps per-thread kernel stacks, so it can call schedule() and
block in the middle of kernel code.  Xen does not keep per-vcpu
hypervisor stacks, so in general it cannot block in the middle of
hypervisor code.

 -George