Re: [Qemu-devel] [PATCH 2/5] lock-guard: add scoped lock implementation

[Eric Blake <eblake@redhat.com>]

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On 12/11/2017 04:16 AM, Stefan Hajnoczi wrote:

>>> I don't understand the need for the qemu_lock_guard_is_taken(&name)
>>> condition, why not do the following?
>>>
>>>   for (QEMU_LOCK_GUARD(type, name, lock);
>>>        ;
>>>        qemu_lock_guard_unlock(&name))
>>
>> Because that would be an infinite loop. :)
> 
> Sorry, I mean for (...; false; ...).  Is there any reason to do
> qemu_lock_guard_is_taken(&name)?

You need the loop to execute at least once ;)

But I proposed an alternative that doesn't need is_taken, by:

for (bool name##done = false, QEMU_LOCK_GUARD(type, name, lock);
     ! name##done; name##done = true)

if we still like the form that declares a for-loop scope.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org


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