[boost] Re: recursive mutex and condition

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2004-11-03 16:47:45

Michael Glassford wrote:
[...]
>       lock lock1(m);
> 
>       //...
> 
>       lock lock2(m); //Recursive lock
> 
>       while (!b)
>          c.wait(lock2); //***
[...]
> deadlock results.

POSIX threads philosophy is that (quoting DRB) "when a thread does 
call another routine while holding a mutex, (with the exception of 
unlock and wait!) the called code MUST assume that the mutex is 
locked because one or more program invariants are broken. That's 
WHY you lock mutexes, and when the invarient is no longer broken, 
you should UNLOCK them. ... If you "spin out" the recursive lock 
to free it, you are breaking the calling code by exposing the 
supposedly protected (broken) invariants to other threads, 
unprepared to handle this." So deadlock isn't that bad. ;-)

See also:

http://lists.boost.org/MailArchives/boost/msg67187.php

regards,
alexander.