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Date: Wed, 12 Mar 2008 13:00:57 +0100
From: Anders Blomdell <anders.blomdell@domain.hid>
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Subject: Re: [Xenomai-help] What have I misunderstood about condition
	variables
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To: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Cc: xenomai-help <xenomai@xenomai.org>

Gilles Chanteperdrix wrote:
> Anders Blomdell wrote:
>  > Gilles Chanteperdrix wrote:
>  > > On Tue, Mar 11, 2008 at 7:19 PM, Anders Blomdell
>  > >>  To me the symptoms indicate that the high priority producer gets the mutex and
>  > >>  signals it before the consumer has properly started to wait on the condition.
>  > > 
>  > > I have not read your program in detail, but what may be your problem
>  > > is that condition variables are not semaphores: if you signal a
>  > > condition variable when nobody is waiting the signal is lost. 
>  > I know this, but the problem is that the program loses signals when it is
>  > waiting. In the consumer:
> 
> Sorry for the noise (and thanks for the patch).
You are welcome.

Small afterthought/question. In the following code:

        xnlock_get_irqsave(&nklock, s);

	...

        mutex->lockcnt = 0;

        if (xnsynch_wakeup_one_sleeper(&mutex->synch_base)) {
                mutex->lockcnt = 1;
                /* Scheduling deferred */
        }

        thread = xnpod_current_thread();

        xnsynch_sleep_on(&cond->synch_base, timeout, XN_RELATIVE);


Am I correct in assuming that no other task (even on a multiprocessor) can claim
the mutex until xnsynch_sleep_on has done its rescheduling?

/Anders


-- 
Anders Blomdell                  Email: anders.blomdell@domain.hid
Department of Automatic Control
Lund University                  Phone:    +46 46 222 4625
P.O. Box 118                     Fax:      +46 46 138118
SE-221 00 Lund, Sweden