[Xenomai-core] switchtest FPU register error on PPC 2.6.18

[Xenomai-core] switchtest FPU register error on PPC 2.6.18

[Wolfgang Grandegger]

Hello,

I just realized the error message:

   Error after context switch from task 8(rtup-8) to task
   10(rtup_ufpp-10), FPU registers were set to 1000 (maybe task
   sleeper_ufps-0)

when running "switchtest" on an PPC under Linux 2.6.18 with Xenomai head 
of SVN. I have attached the full output log. Can some tell me what went 
exactly wrong and where I should start looking at?

Thanks.

Wolfgang.

Re: [Xenomai-core] switchtest FPU register error on PPC 2.6.18

[Gilles Chanteperdrix]

Wolfgang Grandegger wrote:
 > Hello,
 > 
 > I just realized the error message:
 > 
 >    Error after context switch from task 8(rtup-8) to task
 >    10(rtup_ufpp-10), FPU registers were set to 1000 (maybe task
 >    sleeper_ufps-0)
 > 
 > when running "switchtest" on an PPC under Linux 2.6.18 with Xenomai head 
 > of SVN. I have attached the full output log.

Are you sure you did ?

 >  Can some tell me what went 
 > exactly wrong and where I should start looking at?

It means that after a switch from task 8 to task 10, the FPU context is
the one of task 0. So, some context switches which should have switched
the FPU did not. If you are lucky, you should get this error
systematically.

In order to investigate, you should try and reduce the number of tasks
created by switchtest. switchtest --help will tell you the list of tasks
created by switchtest by default, start from this list, and try removing
some tasks, keeping the failure. When you have the minimum set of tasks
that create the failure, try to trace the fpu switches, to see which one
does not do its job correctly.

-- 


					    Gilles Chanteperdrix.

Re: [Xenomai-core] switchtest FPU register error on PPC 2.6.18

[Wolfgang Grandegger]

[-- Attachment #1: Type: text/plain, Size: 1349 bytes --]

Gilles Chanteperdrix wrote:
> Wolfgang Grandegger wrote:
>  > Hello,
>  > 
>  > I just realized the error message:
>  > 
>  >    Error after context switch from task 8(rtup-8) to task
>  >    10(rtup_ufpp-10), FPU registers were set to 1000 (maybe task
>  >    sleeper_ufps-0)
>  > 
>  > when running "switchtest" on an PPC under Linux 2.6.18 with Xenomai head 
>  > of SVN. I have attached the full output log.
> 
> Are you sure you did ?

Oh, well, ... see attachment.

>  >  Can some tell me what went 
>  > exactly wrong and where I should start looking at?
> 
> It means that after a switch from task 8 to task 10, the FPU context is
> the one of task 0. So, some context switches which should have switched
> the FPU did not. If you are lucky, you should get this error
> systematically.
> 
> In order to investigate, you should try and reduce the number of tasks
> created by switchtest. switchtest --help will tell you the list of tasks
> created by switchtest by default, start from this list, and try removing
> some tasks, keeping the failure. When you have the minimum set of tasks
> that create the failure, try to trace the fpu switches, to see which one
> does not do its job correctly.

OK, thanks for the hint. I forgot to mention that it only happens once 
after reboot. Re-exectution does not show the error any more.

Wolfgang.


[-- Attachment #2: switchtest-error.log --]
[-- Type: text/x-log, Size: 1517 bytes --]

bash-3.00# cd xenomai/testsuite/switchtest/
bash-3.00# ./run
*
*
* Type ^C to stop this application.
*
*
== Testing FPU check routines...
r0: 1 != 2
r1: 1 != 2
r2: 1 != 2
r3: 1 != 2
r4: 1 != 2
r5: 1 != 2
r6: 1 != 2
r7: 1 != 2
r8: 1 != 2
r9: 1 != 2
r10: 1 != 2
r11: 1 != 2
r12: 1 != 2
r13: 1 != 2
r14: 1 != 2
r15: 1 != 2
r16: 1 != 2
r17: 1 != 2
r18: 1 != 2
r19: 1 != 2
r20: 1 != 2
r21: 1 != 2
r22: 1 != 2
r23: 1 != 2
r24: 1 != 2
r25: 1 != 2
r26: 1 != 2
r27: 1 != 2
r28: 1 != 2
r29: 1 != 2
r30: 1 != 2
r31: 1 != 2
== FPU check routines: OK.
== Threads: sleeper_ufps-0 rtk-1 rtk-2 rtk_fp-3 rtk_fp-4 rtk_fp_ufpp-5 rtk_fp_ufpp-6 rtup-7 rtup-8 rtup_ufpp-9 rtup_ufpp-10 rtus-11 rtus-12 rtus_ufps-13 rtus_ufps-14 rtuo-15 rtuo-16 rtuo_ufpp-17 rtuo_ufpp-18 rtuo_ufps-19 rtuo_ufps-20 rtuo_ufpp_ufps-21 rtuo_ufpp_ufps-22
r0: 1000 != 10
r1: 1000 != 10
r2: 1000 != 10
r3: 1000 != 10
r4: 1000 != 10
r5: 1000 != 10
r6: 1000 != 10
r7: 1000 != 10
r8: 1000 != 10
r9: 1000 != 10
r10: 1000 != 10
r11: 1000 != 10
r12: 1000 != 10
r13: 1000 != 10
r14: 1000 != 10
r15: 1000 != 10
r16: 1000 != 10
r17: 1000 != 10
r18: 1000 != 10
r19: 1000 != 10
r20: 1000 != 10
r21: 1000 != 10
r22: 1000 != 10
r23: 1000 != 10
r24: 1000 != 10
r25: 1000 != 10
r26: 1000 != 10
r27: 1000 != 10
r28: 1000 != 10
r29: 1000 != 10
r30: 1000 != 10
r31: 1000 != 10
Error after context switch from task 8(rtup-8) to task 10(rtup_ufpp-10),
FPU registers were set to 1000 (maybe task sleeper_ufps-0)
RTT|  00:00:00
RTH|ctx switches|-------total
RTD|          28|          28