[boost] Re: Lock unification (shared vs. upgradable)

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2004-08-09 12:26:37

On Aug 9, 2004, at 10:26 AM, Alexander Terekhov wrote:

> Yes, but this scheme has a drawback. "Serial wakes across context
> switching" (in addition to locking across context switching). For
> alternative, see (for example)
>
> http://groups.google.com/groups?selm=3D9196B2.9BC29299%40web.de
> (Subject: Re: rwlock using pthread_cond)

The alternative in this link looks very familiar.  I'm currently using  
two condition variables, an unsigned, and two bools (oh, and of course  
the mutex).  Although after looking at your example I think I could  
probably merge my unsigned and two bools into an int and one bool  
(because of padding, may not be worth the effort though).  My two  
condition variables are used slightly differently than yours because of  
the additional requirements of:

start_upgradable()
end_upgradable()

(
and of course there's the conversion-functions:

http://home.twcny.rr.com/hinnant/cpp_extensions/ 
threads.html#unlock_and_lock_sharable
)

Sorry I can't just show the code.

-Howard