Messages in this thread | | | Date | Wed, 06 Jul 2016 12:58:11 +0800 | From | xinhui <> | Subject | Re: [PATCH v2 2/4] powerpc/spinlock: support vcpu preempted check |
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Hi, wanpeng
On 2016年07月05日 17:57, Wanpeng Li wrote: > Hi Xinhui, > 2016-06-28 22:43 GMT+08:00 Pan Xinhui <xinhui.pan@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? > There is one shard struct between kernel and powerVM/KVM. And we read the yield_count of this struct to detect if one vcpu is running or not. SO it's easy for ppc to implement such interface. Note that yield_count is set by powerVM/KVM. and only pSeries can run a guest for now. :)
I also review x86 related code, looks like we need add one hyer-call to get such vcpu preemption info?
thanks xinui > Regards, > Wanpeng Li >
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