Re: SMP related question

[Sebastian Huber]

Hello Stavros,

On 22/08/18 12:43, Passas, Stavros wrote:


Hi all,

My main objective was to have a way to run the rtems testsuite and 
have a script auto-compare the results with the corresponding scn file.


Currently, just because core0 starts core1, seems like core1 always 
starts Init(), all results are flipped, thus this process cannot be 
automated.


Functionality wise, everything runs as expected, I verified 
individually each core with the debugger, so I am ok with it.


Also, this issue comes up in a different form also when the 
applications exits, because core1 (that had started Init(), exits with 
the expected return code, while all other cores terminate with 
RTEMS_FATAL_SOURCE_SMP/SMP_FATAL_SHUTDOWN_RESPONSE, which is handled 
as an error at the moment from the debugger/loader. For the moment I 
have added a fatal extension handler to avoid this case, but I am 
still looking if there is any better solution.




I think a long term solution is to use a new test framework which 
produces machine readable output.


https://devel.rtems.org/ticket/3199

The only machine readable output is currently the begin/end of test 
message. We try currently to get some budget for this. Please let me 
know if you are interested to contribute to something in this area.


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RE: SMP related question

[Passas, Stavros]

Hi all,

My main objective was to have a way to run the rtems testsuite and have a 
script auto-compare the results with the corresponding scn file.
Currently, just because core0 starts core1, seems like core1 always starts 
Init(), all results are flipped, thus this process cannot be automated.
Functionality wise, everything runs as expected, I verified individually each 
core with the debugger, so I am ok with it.

Also, this issue comes up in a different form also when the applications exits, 
because core1 (that had started Init(), exits with the expected return code, 
while all other cores terminate with 
RTEMS_FATAL_SOURCE_SMP/SMP_FATAL_SHUTDOWN_RESPONSE, which is handled as an 
error at the moment from the debugger/loader. For the moment I have added a 
fatal extension handler to avoid this case, but I am still looking if there is 
any better solution.

Best Regards,
   Stavros

From: users [mailto:users-boun...@rtems.org] On Behalf Of Joel Sherrill
Sent: Monday, August 20, 2018 5:39 PM
To: Sebastian Huber 
Cc: rtems-us...@rtems.org 
Subject: Re: SMP related question



On Mon, Aug 20, 2018 at 1:23 AM, Sebastian Huber 
mailto:sebastian.hu...@embedded-brains.de>> 
wrote:


On 12/08/18 00:41, Chris Johns wrote:
On 10/08/2018 22:30, Sebastian Huber wrote:
Hello Stavros,

you can do this with a custom clustered scheduler configuration:

https://docs.rtems.org/branches/master/c-user/configuring_a_system.html#clustered-scheduler-configuration
I had a brief look over the documentation you provided but could not see how to
achieve the result you are saying.

Stavros, asked for two things.

1. A way to change properties of the initialization task which are not covered 
by configuration options

https://docs.rtems.org/branches/master/c-user/configuring_a_system.html#classic-api-initialization-tasks-table-configuration

before the initialization task runs. To do this some user provided code must 
execute after the initialization task is created and before it runs. My 
suggestion to use a device driver initialization function for this doesn't 
work. The initialization task is created after the device driver 
initialization. It can be done via a system initialization handler using the 
undocumented RTEMS_SYSINIT_ITEM(). Maybe also a high priority constructor, 
however, in this case the task already runs.

The high priority constructor is too late if the goal is to avoid any activity 
except core 0.

RTEMS_SYSINIT_ITEM() would work but adding a confdefs.h item for SMP 
configurations to pin the thread to a single core seems like a simple solution.


2. A way to pin a task to a particular processor. There are two options to do 
this in RTEMS. One is a clustered scheduler configuration, the other is the use 
of a thread to processor affinity.

I think being able to pin the Init thread to a single core would be a nice 
confdefs.h feature. Not specifying a full cpuset, just the core number.

I don't think this use case is enough by itself to force a user to clustered 
scheduling with core 0 an instance by itself.



Alternatively, on a recent version the default SMP scheduler supports a 
one-to-one affinity.  You can set it in a device driver.
Is there an example of how to do this?

As Sebastian points out, you can't do it in a device driver. But no, there is 
no example specifically for the Init thread.
There are smptests which do this but likely no proper example of setting 
affinity, scheduler, etc.

--joel


Chris
- Am 10. Aug 2018 um 14:10 schrieb Passas, Stavros 
stavros.pas...@intel.com:
Hi,

In my local SMP enabled RTEMS, I notice core1 starting the Init() function of
the user application.
Is there a way to enforce RTEMS to run the Init() in the boot processor, when
SMP is enabled?

Best Regards,
   Stavros
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Fax : +49 89 189 47 41-09
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