users Digest, Vol 146, Issue 25

[Arturo Perez Garcia]

I didn't call rtems_semaphore_release in the Init task, because the 
initial count of the semaphore is 1. So that was not the case.

I followed the guidelines described in RTEMS C User Documentation 
Release 4.11.3. Section 12.2 paragraph 2:

"A binary semaphore can be used to control access
to a single resource. In particular, it can
be used to enforce mutual exclusion for a critical
section in user code. In this instance, the
semaphore would be created with an initial
count of one to indicate that no task is executing
the critical section of code..."

Thanks



El 2018-11-28 13:00, users-request at rtems.org escribió:
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>    1. Re: Task sync problems related with binary semaphore and
>       cache memories (Sebastian Huber)
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> ----------------------------------------------------------------------
> 
> Message: 1
> Date: Wed, 28 Nov 2018 11:58:11 +0100
> From: Sebastian Huber <sebastian.huber at embedded-brains.de>
> To: Arturo Perez Garcia <arturo.perez at upm.es>
> Cc: users at rtems.org
> Subject: Re: Task sync problems related with binary semaphore and
> 	cache memories
> Message-ID: <de80b7c0-3174-6fe0-d4ba-98dbc647b241 at embedded-brains.de>
> Content-Type: text/plain; charset=utf-8; format=flowed
> 
> On 28/11/2018 11:52, Arturo Perez Garcia wrote:
>> Yes, I'm checking the return status always. When I create the RTEMS
>> objects and when I acquire/release the semaphore. I removed those
>> checks from the code I put in the previous message.
> 
> Ok, good.
> 
>> 
>> Thanks.
>> 
>> El 2018-11-28 11:42, Sebastian Huber escribi?:
>>> On 28/11/2018 11:30, Arturo Perez Garcia wrote:
>>>> Disabling the caches don't fixe the problem, I was wrong.
>>>> 
>>>> Maybe I'm initializing wrongly the RTEMS objects.
>>>> 
>>>> In the Init task I create the binary semaphore:
>>>> 
>>>> ?????? rtems_semaphore_create(a3_sem_name, 1, RTEMS_BINARY_SEMAPHORE
>>>> | RTEMS_FIFO | RTEMS_LOCAL, 0, &a3_sem_id);
> 
> This call creates a binary semaphore without a locking protocol which 
> is
> owned by the current task (Init task). If you do not call
> rtems_semaphore_release() for this semaphore within the Init task, then
> no other task should be able to obtain it.
> 
> I would debug the rtems_semaphore_obtain() call if this is actually the
> case.
> 
> --
> Sebastian Huber, embedded brains GmbH
> 
> Address : Dornierstr. 4, D-82178 Puchheim, Germany
> Phone   : +49 89 189 47 41-16
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> E-Mail  : sebastian.huber at embedded-brains.de
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> End of users Digest, Vol 146, Issue 25
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-- 
Arturo Perez Garcia - arturo.perez at upm.es

Researcher
Center of Industrial Electronics
Universidad Politecnica de Madrid