Re: [Qemu-devel] [RFC v4 16/28] tcg: drop global lock during TCG code execution

[Richard Henderson]

On 09/06/2016 10:43 PM, Paolo Bonzini wrote:
> On 07/09/2016 06:03, Richard Henderson wrote:
> > > +    if (mr->global_locking) {
> > > +        qemu_mutex_lock_iothread();
> > > +        locked = true;
> > > +    }
> > >      memory_region_dispatch_read(mr, physaddr, &val, 1 << SHIFT,
> > >                                  iotlbentry->attrs);
> > > +    if (locked) {
> > > +        qemu_mutex_unlock_iothread();
> > > +    }
> >
> > I'm not keen on this pattern.
> >
> > (1) Why not use recursive locks?
>
> Probably I'm biased by looking at this code too long, but... how would
> they help?

You wouldn't check to see if the lock is already taken.


r~