Subj : Re: Avoiding synchronization (pthreads)
To   : comp.programming.threads
From : Marcin 'Qrczak' Kowalczyk
Date : Wed Mar 02 2005 10:58 pm

"Joe Seigh" <jseigh_01@xemaps.com> writes:

>> Yes. Are there architectures where one thread decrementing an int can
>> cause another thread which doesn't use a memory barrier see the value
>> which has nothing to do with the actual range of values of this int?
>
> You need the barrier to prevent reads of the shared data occuring before
> the fetch of the count.  You only need to do it once after seeing the
> count go to one thread.  Kind of like DCL but with multiple initializers.

Ah, I think I understand.

I fixed the code to have a cache of this variable accessed outside the
mutex by a single thread, updated from the real variable inside the mutex.

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/

.