Re: [Qemu-devel] [RFC] block: Removed coroutine ownership assumption

[Peter Maydell]

On 22 June 2012 13:04, Markus Armbruster <address@hidden> wrote:
> Peter Maydell <address@hidden> writes:
>
>> On 22 June 2012 09:48, Markus Armbruster <address@hidden> wrote:
>>> In my opinion, coroutines have been useful for us so far.  Whether they
>>> remain useful, or serve us just as a stepping stone towards general
>>> threads remains to be seen.
>>
>>>From my point of view I've seen a whole pile of problems and not
>> really any advantages...
>
> Advantages over what?

Over what we had before we had coroutines. I know there are
advantages, I'm just saying that personally I've been largely
on the downside rather than the upside.

>>                          I particularly think it's a really bad
>> idea to have a complex and potentially race-condition-prone bit
>> of infrastructure implemented three different ways rather than
>> having one implementation used everywhere -- it's just asking
>> for obscure bugs on the non-x86 hosts.
>
> Fair point, but it's an implementation problem, not a fundamental
> problem with coroutines.  You *can* implement coroutines portably,
> e.g. on top of gthread.

If you're implementing them on top of separate threads then
you just have an obfuscated API to threads.

-- PMM