Re: [Xenomai] Make a block of code atomic

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 07/09/2013 01:40 PM, Paolo Minazzi wrote:

> Hi,
>
> I would like to make a block of kernel code atomic, so that no one (both
> xenomai and Linux) can interrupt it.
> I use the following :
>
> #define my_local_irq_save(x)    ((x) =
> ipipe_test_and_stall_pipeline_head()&  1)
> #define my_local_irq_restore(x) ipipe_restore_pipeline_head(x)
>
> my_local_irq_save(flags);
> <  critical section>
> my_local_irq_restore(flags);
>
> It works well enough, but rarely an rtdm irq enter into my critical
> section.
> The rtdm irq is registered in this way : rtdm_irq_request(&priv->irqHnd,
> ETH_PORT_IRQ_NUM(priv->port), irqHandler, RTDM_IRQTYPE_EDGE, "rtdm_eth",
> priv);
>
> Is it normal ? Are you sure that it cannot happen ?


Looking at ipipe_test_and_stall_head implementation on the I-pipe patch 
for Linux 3.8:

static inline unsigned long ipipe_test_and_stall_head(void)
{
	hard_local_irq_disable();
	return __test_and_set_bit(IPIPE_STALL_FLAG, &__ipipe_head_status);
}

getting an interrupt in your critical section would mean that 
"hard_local_irq_disable" is broken on the architecture where you use it.

That being said, I do not know if I look at the implementation you are 
using, since you did not give us any information about version and 
architecture you are using.

-- 
                                                                 Gilles.