On Mon, 22 Jan 2007 11:56:30 -0800, Andrew Morton <[EMAIL PROTECTED]> wrote:
> > On Tue, 16 Jan 2007 02:47:10 +0100 "J.A. Magallón" <[EMAIL PROTECTED]>
> > wrote:
> > Hi...
> >
> > I run the (almost) latest -mm kernel (2.6.20-rc3-mm1), and see some strange
> > behaviour
> > with POSIX threads (glibc-2.4).
> > I have downgraded my test to a simple textboox example for a SMP-safe spool
> > queue, it's just a circular queue with a mutex and a condition variable for
> > in
> > and out. I have seen the same structure in several places.
> >
> > Well, it just sometimes gets blocked. GDB says its stuck in pthread_wait().
> > I could swear it worked on previous kernels. It works as is on IRIX.
> > I will try to build an older kernel to test.
> > I takes a second to block it with something like while :; tst; done.
> >
> > Any ideas ?
>
> Do I need to worry about this still?
Oops, no, sorry. It was buggy code that previously seemed to work.
Buggy code:
pthread_mutex_lock(&slots_mutex);
while (slots<=0)
pthread_cond_wait(&slots_cond,&slots_mutex);
slots--;
items++;
pthread_mutex_unlock(&slots_mutex);
pthread_mutex_lock(&items_mutex);
pthread_cond_signal(&items_cond);
pthread_mutex_unlock(&items_mutex);
(buggy because it acceses items without locking. The same in the other
endpoint of the queue).
Correct code:
pthread_mutex_lock(&slots_mutex);
while (slots<=0)
pthread_cond_wait(&slots_cond,&slots_mutex);
slots--;
pthread_mutex_unlock(&slots_mutex);
pthread_mutex_lock(&items_mutex);
items++;
pthread_cond_signal(&items_cond);
pthread_mutex_unlock(&items_mutex);
So don't worry. I was so busy I forgot to post the solution.
--
J.A. Magallon <jamagallon()ono!com> \ Software is like sex:
\ It's better when it's free
Mandriva Linux release 2007.1 (Cooker) for i586
Linux 2.6.19-jam04 (gcc 4.1.2 20061110 (prerelease)
(4.1.2-0.20061110.2mdv2007.1)) #0 SMP PREEMPT
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