Re: [PATCH v2 0/7] swait: Introduce and use swq_has_sleeper()

[Paolo Bonzini]

On 13/09/2017 22:08, Davidlohr Bueso wrote:
> The following patches fix and/or justify (in baby steps) some of the
> callers. The main exception is s390, which I didn't follow how ->valid_wakeup
> can get hoisted as kvm_vcpu_block does not use that in the wait loop.

valid_wakeup is just an optimization, so it's not a problem.

There seems to be always an atomic_or or set_bit before
kvm_s390_vcpu_wakeup is called (except kvm_s390_idle_wakeup which has no
store at all and doesn't need any serialization).  So my suggestion is
to add an smp__mb_after_atomic in kvm_s390_vcpu_wakeup; I'll let the
s390 guys do it.

Paolo