Hitachi djprobe mechanism

[Andi Kleen]

> step 2: safety check;
>         make sure that all CPUs don't run on the code that will
>         be replaced with jmp instruction (also check whether stack
>         include EIP of the code which is subject to replace)

I don't think there is a race free way to do this without an IPI to 
all CPUs. And if you do that you can as well do it simpler.

> step 4: i-cache flush or serializing:
>         invoke i-cache flush instruction such as CLFLASH or serialize
>         instruction such as CPUID on all CPUs (new step)

I'm not sure these flushes are needed. With IPIs certainly not.

-Andi