On Thu, Jul 23, 2015 at 11:08:39PM -0700, Andy Lutomirski wrote:
> To be obviously safe against any local exception, we want a single
> instruction that will change %rsp and some in-memory flag at the same
> time. There aren't a whole lot of candidates. Cmpxchg isn't useful
> (cmpxchg with a memory operand doesn't modify its register operand).
Why would you even need that?
You do LOCK; CMPXCHG on a per_cpu variable and then test ZF? I.e., use
it as a mutex in asm. With ZF=1, you switch stacks, with ZF=0, you
busy-wait ...
Or am I missing something?
This way you serialize all irq stack switchers...
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
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