Re: [Gomp-discuss] Decision about semaphores ..

[Lars Segerlund]

 I have looked at libc's semaphores, but it's explicitly stated that 
they are not SMP safe ! ( even a bit unsure about how they would work 
with native linux threads ).

 You use a semaphore for a join in the following fashion, every thread 
which is started increases the value of the semaphore ( starts an 0 ), 
when theyre finished they atomically decrease it, and the thread which 
sets it to null uses a signal to signal the join. ( also works for 
barriers and synchronisation ).

 Threads which have decreased the semaphore waits on the signal, and 
the main thread can do the same.

 I was thinking of using a condition ( cond ) in the threading lib, 
which is easy to wait on ( not busy, so sleep on would be more 
appropriate ).

/ Lars Segerlund.

Pop Sébastian wrote:
> On Wed, Feb 19, 2003 at 11:08:25AM +0100, Steven Bosscher wrote:
>
> > Would you mind explaining to the not-a-computer-scientist here what a
> > semaphore is? :-)
>
>
> > From "info libc" section "POSIX Semaphores":
>
>    Semaphores are counters for resources shared between threads. The
> basic operations on semaphores are: increment the counter atomically,
> and wait until the counter is non-null and decrement it atomically.
>
>
>
> _______________________________________________
> Gomp-discuss mailing list
> address@hidden
> http://mail.nongnu.org/mailman/listinfo/gomp-discuss