Re: [Xen-devel] credit scheduler and HYPERVISOR_yield()

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 15/10/07 18:13, "Emmanuel Ackaouy" <ackaouy@xxxxxxxxx> wrote:

> In the case of IPIs, you're already going into the hypervisor so you
> should be able to do something straightforward with a sleeping
> semaphore. Maybe you spin a little before you sleep though to give
> running VCPUs a chance to respond before you give up the end of
> your time slice.

Actually a blocking spinlock could be implemented with no Xen changes.
Change the spinlock function in Linux to spin a few times and then set a
waiting bit in a cpumask and then SCHEDOP_poll on a per-VCPU spinlock-wakeup
event channel. On spin_unlock, the unlocker sends an event to any VCPU in
the cpumask, using each VCPU's spinlock-wakeup event channel.

Yes, this is probably nicer than using yield() and praying.

 -- Keir



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