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Date: Wed, 12 Nov 2014 10:10:17 +0100
From: Philippe Gerum <rpm@xenomai.org>
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Subject: Re: [Xenomai] rtdm_nrtsig_pend FAQ
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To: johann.obermayr@sigmatek.at, "Xenomai@xenomai.org" <Xenomai@xenomai.org>

On 11/12/2014 09:47 AM, Johann Obermayr wrote:
> Hello,
> 
> we use rtdm_nrtsig_pend follow.
> 
> static rtdm_nrtsig_t wait_domain_nrt;
> static DECLARE_WAIT_QUEUE_HEAD(wait_domain_wq);
> 
> void period_update()
> {
>         wait_domain_pend_count++;
>         rtdm_nrtsig_pend(&wait_domain_nrt);
> }
> 
> static void wait_domain_nrt_handler(rtdm_nrtsig_t nrt_sig, void *arg)
> {
>     wait_domain_call_count++;
>     //wakeup wait_domain
>     wait_domain_wakeup = 1;
>     wake_up_interruptible(&wait_domain_wq);
> }
> 
> 
> period_update is called every millisecond.
> this is on imx6 hardware with kernel 3.0.x and xenomai 2.6.2.1.
> 
> Why wait_domain_call_count can be smaller that wait_domain_pend_count.
> The difference between the counters is growing.
> 
> Why ?
> 

nrt signals are based on I-pipe virtual irqs, which do not pile up:
there is a single signal pending until the irq can be delivered to the
handler, regardless of how many times it has been triggered.

-- 
Philippe.