Subj : Re: double-checked locking in C
To   : comp.programming.threads
From : Joe Seigh
Date : Tue Jul 05 2005 07:10 pm

amorox@gmail.com wrote:
> Hi,
> 
> I would like to use the DCL idiom (double-checked locking) to guarantee
> the once and only once execution of an initialization code:
> 
> bool initialized = false;
> pthread_mutex_t mutex;
> 
> void function(void)
> {
>    if (!initialized) {
>       pthread_mutex_lock(&mutex);
>       if (!initialized) {
>          initialized = true;
>          init_code();
>       }
>       pthread_mutex_unlock(&mutex);
>    }
> }
> 
> I know that in Java there were problems with this idiom due to the
> memory operation reorderings and these have been apparently solved in
> Java 1.4.
> 
> Is there any problem using this idiom in a multithread C program? If
> affirmative would you explained why?
> 
> Thanks,
> Ovi
> 
> P.S.: I know the problem may be solved by using 'pthread_once'
> protection.
> 

http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

.