Re: [qemu-s390x] [Qemu-devel] [RFC v4 24/71] s390x: convert to cpu_halted

[Alex Bennée]

Emilio G. Cota <address@hidden> writes:

> On Wed, Oct 31, 2018 at 16:13:05 +0000, Alex Bennée wrote:
>> > @@ -353,10 +355,12 @@ void s390_cpu_unhalt(S390CPU *cpu)
>> >      CPUState *cs = CPU(cpu);
>> >      trace_cpu_unhalt(cs->cpu_index);
>> >
>> > -    if (cs->halted) {
>> > -        cs->halted = 0;
>> > +    cpu_mutex_lock(cs);
>> > +    if (cpu_halted(cs)) {
>> > +        cpu_halted_set(cs, 0);
>> >          cs->exception_index = -1;
>> >      }
>> > +    cpu_mutex_unlock(cs);
>>
>> I think this locking is superfluous as you already added locking when
>> you introduced the helper.
>
> It gives a small perf gain, since it avoids locking & unlocking twice
> in a row (cpu_halted and cpu_halted_set both take the lock if needed).

Maybe a one line comment then above the first lock:

  /* lock outside cpu_halted(_set) to avoid bouncing */

Or some such.....

>
>> Otherwise:
>>
>> Reviewed-by: Alex Bennée <address@hidden>
>
> Thanks!
>
>               Emilio


--
Alex Bennée