[boost] Re: no semaphores in boost::thread

From: Nicolas Fleury (nfleury_at_[hidden])
Date: 2003-06-04 16:08:37

Alexander Terekhov wrote:
> Nicolas Fleury wrote:
> 
>>Thx for the link, but I don't get it.  How is Microsoft implementation
>>of semaphore is showing that all implementations of semaphore should be
>>avoided?  
> 
> It is showing that semas (e.g. bin-semas aka "auto-reset events")
> are really error-prone. Their implementation of counting semaphore

How?

> using a mutex (well, they actually use a totally brain-damaged 
> "dying spinlock") plus a binary semaphore is buggy (it contains 
> erroneous synchronization). Now... you might to follow this link:

Why buggy?

> "Pthreads win32 is just trying to be a general pupose condition 
>  variable as defined by the pthreads standard, suitable for any 
>  and all threads to go around calling pthread_cond_wait() and 
>  pthread_cond_signal() on. As a consequence the implementation 
>  contains several mutexes, semaphores etc, and a flow of control 
>  that will make your brains dribble out of your ears if you stare 
>  at the code too long (I have the stains on my collar to prove it
>  ;-). Such are the joys of implementing condition variables using 
>  the Win32 synchronization primitives!"  

But what's the relation between Microsoft implementation of semaphore, 
pthread win32 implementation of condition and the error-proness of 
semaphores versus mutexes/conditions in general?

Is it simply a mather of preference and style, or is there a simple case 
to show why semaphores are error-prone instead of mutexes/conditions?

Regards.
Nicolas Fleury