Re: [PATCH 4/6] coroutine-lock: reimplement CoRwLock to fix downgrade bug

[Paolo Bonzini <pbonzini@redhat.com>]

On 17/03/21 16:17, David Edmondson wrote:
>> +    if (tkt) {
>> +        if (tkt->read) {
>> +            if (lock->owners >= 0) {
>> +                lock->owners++;
>> +                co = tkt->co;
>> +            }
>> +        } else {
>> +            if (lock->owners == 0) {
>> +                lock->owners = -1;
>> +                co = tkt->co;
>> +            }
>> +        }
>> +    }
>> +
>> +    if (co) {
>> +        QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next);
>> +        qemu_co_mutex_unlock(&lock->mutex);
>> +        aio_co_wake(co);
>> +    } else {
>> +        qemu_co_mutex_unlock(&lock->mutex);
>> +    }
> 
> This block could be pushed up into the earlier block, but I imagine that
> the compiler will do it for you.

I guess I could do

     if (!tkt || (tkt->read ? lock->owners < 0 : lock->owners != 0)) {
         qemu_co_mutex_unlock(&lock->mutex);
         return;
     }
     if (tkt->read) {
         lock->owners++;
     } else {
         lock->owners = -1;
     }

     co = tkt->co;
     QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next);
     qemu_co_mutex_unlock(&lock->mutex);
     aio_co_wake(co);

but I find it less readable.  So that leaves only the of/or typo, right?

Paolo