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

[Richard Henderson]

On 08/11/2016 08:24 AM, Alex Bennée 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?

(2) If there's a good reason why not, then perhaps

  if (mr->global_locking) {
    qemu_mutex_lock_iothread();
    do_something;
    qemu_mutex_unlock_iothread();
  } else {
    do_something;
  }

is a better pattern to use.


r~