FW: RTEMS Message Queue Behaviour

Jamie Bowman jamie.bowman at steepestascent.com
Fri Apr 9 14:16:15 UTC 2010


There are 15 threads, each of which will send messages to the Logging thread
via the Logging Message Queue. 

In the case where we are seeing messages coming out of order, only a single
thread is active and therefore there is only one thread sending messages to
the logging thread.

The LOGMSG is not a global variable, as in there is a local version for each
thread. LOGMSG is actually a structure containing some variables and
character messages. 

I can definitely confirm that all task creation and starts, message queue
creation and sends all return no error.

>From our latest debug we have the following scenario:

	Send Message 1  (status = 0)			Received Message 1 
	Send Message 2  (status = 0)			Received Message 2 
	Send Message 3  (status = 0)			Received Message 3 
	Send Message 4  (status = 0)			Received Message 4 
	Send Message 5  (status = 0)
	PAUSE 10 Seconds					PAUSE 10
	Send Message 6  (status = 0)			Received Message 6

	Send Message 7  (status = 0) 			Received Message 5 
	Send Message 8  (status = 0) 			Received Message 7 
	Send Message 9  (status = 0) 			Received Message 8
	Send Message 10 (status = 0)

Kind regards


Jamie Bowman
Steepest Ascent Ltd
Ladywell, 94 Duke Street, Glasgow, G4 0UW, UK
t: +44 (0) 141 552 8855
e: jamie at steepestascent.com
w: www.steepestascent.com 

-----Original Message-----
From: Joel Sherrill [mailto:joel.sherrill at oarcorp.com] 
Sent: 09 April 2010 13:29
To: Aleix Conchillo Flaqué
Cc: Jamie.Bowman at steepestascent.com; rtems-users at rtems.org
Subject: Re: FW: RTEMS Message Queue Behaviour

On 04/09/2010 06:51 AM, Aleix Conchillo Flaqué wrote:
> Then, I don't know. Probably Joel or others can help you, but it seems
> to me an application problem.
> About the message order, this can simply be a task priority issue,
> unless you sent all messages from the same task, which I guess is what
> you did to try this out.
Are the messages sent from ISRs?  That introduces
the possibility of a critical section issue which is not
present if all logging is from a task.

Can you quit printing and simply set a boolean array
for sent/received base on the message number?

Just to confirm .. all message queue sends return
successful, right?

Is the LOGMSG a global variable or potentially
shared between multiple senders?


> On Fri, Apr 9, 2010 at 13:32, Jamie Bowman
> <jamie.bowman at steepestascent.com>  wrote:
>> Aleix
>> My apologies!
>> Good call on the rtems_message_queue_receive parameters. However by
>> both RTEMS_WAIT and RTEMS_NO_TIMEOUT are defined as zero, so it wouldn't
>> change the parameters actually sent to rtems_message_queue_receive.
>> Kind regards
>>         Jamie
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