On Friday 19 January 2001 15:23, Mike Kravetz wrote:
> On Fri, Jan 19, 2001 at 02:03:06PM -0800, Davide Libenzi wrote:
> <stuff deleted>
>
> > > void oneatwork(int thr)
> > > {
> > > int i;
> > > while (!start) /* don't disturb pthread_create() */
> > > usleep(10000);
> > >
> > > actthreads++;
> > > while (!stop)
> > > {
> > > if (count)
> > > totalwork[thr]++;
> > >
> > > syscall(158); /* sys_sched_yield() */
> > > }
> > > actthreads--;
> > > pthread_exit(0);
> > > }
> > >
> > > Note that actthreads is a global variable which is being updated
> > > by multiple threads without any form of synchronization. Because
> > > of this actthreads sometimes never goes to zero after all worker
> > > threads have finished.
> >
> > If all threads complete successfully actthreads has to be zero.
>
> Not as currently coded. If two threads try to decrement actthreads
> at the same time, there is no guarantee that it will be decremented
> twice. That is why you need to put some type of synchronization in
> place.
Right, inc & dec are not atomic w/o #LOCK.
- Davide
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