[PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check

[Wanpeng Li]

Hi Xinhui,
2016-06-28 22:43 GMT+08:00 Pan Xinhui <xinhui.pan at linux.vnet.ibm.com>:
> This is to fix some lock holder preemption issues. Some other locks
> implementation do a spin loop before acquiring the lock itself. Currently
> kernel has an interface of bool vcpu_is_preempted(int cpu). It take the cpu
> as parameter and return true if the cpu is preempted. Then kernel can break
> the spin loops upon on the retval of vcpu_is_preempted.
>
> As kernel has used this interface, So lets support it.
>
> Only pSeries need supoort it. And the fact is powerNV are built into same
> kernel image with pSeries. So we need return false if we are runnig as
> powerNV. The another fact is that lppaca->yiled_count keeps zero on
> powerNV. So we can just skip the machine type.

Lock holder vCPU preemption can be detected by hardware pSeries or
paravirt method?

Regards,
Wanpeng Li