Re: [boost] [thread] RFC standard proposed mutex, read-write mutex, condition

From: Yuval Ronen (ronen_yuval_at_[hidden])
Date: 2007-08-26 17:47:31

Howard Hinnant wrote:
> 
> At this point I'm really leaning towards getting back to basics:

<snip options for class condition>

It seems I wasn't very successful in convincing, so I'll try one last 
time. I strongly recommend you seriously consider

template <class Mutex>
class condition
{
     condition();
     explicit condition(Mutex &); // or Mutex*

     void set_mutex(Mutex &); // or Mutex*
     void wait();
     // more wait() overloads with predicate and timeout
     // and of course the notify functions
};

I'll repeat the advantages I see for this approach:

1. It can work for any user-defined mutex.
2. Yet it can be specialized for better sizeof for std::mutex.
3. It can be made to check for errors (not assigning a mutex or not 
locking the mutex) when calling wait().
4. Yet it can be made to be as-fast-as-possible.
5. It can dynamically switch the mutex which the condition works for 
(for the rare cases when it is needed).
6. It allows easily using the condition in a deeper function than the 
one that locked the mutex.
7. It doesn't force using locks (which I see as a plus, because there's 
a reason we brought mutex back his lock/unlock).
8. It doesn't introduce an unprecedented technique of "encouraging" 
users to lock (by passing a lock to a function). A technique which I 
find to be cumbersome and misleading (because it works only partially).

Unfortunately I have to leave in an hour for two weeks, so I'm out of 
this discussion for now, but please don't dismiss this idea without 
careful thought.

Yuval