From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <51DD4760.6050908@xenomai.org>
Date: Wed, 10 Jul 2013 13:37:04 +0200
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
MIME-Version: 1.0
References: <51DBF6B8.1000000@mitrol.it>
In-Reply-To: <51DBF6B8.1000000@mitrol.it>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Xenomai] Make a block of code atomic
List-Id: Discussions about the Xenomai project <xenomai.xenomai.org>
List-Unsubscribe: <http://www.xenomai.org/mailman/options/xenomai>,
	<mailto:xenomai-request@xenomai.org?subject=unsubscribe>
List-Archive: <http://www.xenomai.org/pipermail/xenomai>
List-Post: <mailto:xenomai@xenomai.org>
List-Help: <mailto:xenomai-request@xenomai.org?subject=help>
List-Subscribe: <http://www.xenomai.org/mailman/listinfo/xenomai>,
	<mailto:xenomai-request@xenomai.org?subject=subscribe>
To: Paolo Minazzi <Paolo.Minazzi@mitrol.it>
Cc: xenomai@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.