Re: [Xenomai-core] [PATCH] Add fptest for powerpc

[Heikki Lindholm <holindho@domain.hid>]

Gilles Chanteperdrix kirjoitti:
> Heikki Lindholm wrote:
>  > This adds powerpc version of fptest.h. It just stores and loads the raw 
>  > integer into/from FPU registers without converting to proper IEEE form. 
>  > Converting would have added unneccessary complexity. As a side note, the 
>  > ppc barfs on the test with "1000 != 10". :I
> 
> Ok, this test tool is far from being user-friendly :-)
> 
> Just to be sure, I have tested the latest revision on x86 and it still
> runs fine, so I guess there really is a bug in power pc fpu switching
> code.
> 
> Now, if we decode a bit, the integer passed to fp_regs_set and
> fp_regs_check are 1000 * iterations + task_index, so
> 1000 is task 0, iteration 1
> 10 is task 10, iteration 0.
> It means that task 10 after returning from its first context 
> switch, is getting the context of task 0 before its second context
> switch.
> 
> Now the thing to try is to reduce the number of threads involved, since
> by default there are 23 threads, so you should add a printk for each
> context switch in the kernel driver (and now that I think about it this
> printk should be activable with an ioctl), and try and reduce the list
> of threads by removing threads which do not appear between the serie of
> switches from task 0 to task 10. The correspondance between the task
> numbers and their type is not easy, but /proc/xenomai/sched and switch
> --help should help... 
> 
> Task 0 is the "idle" taks, an ordinary Linux task
> Task 10 is of type "rtup_ufpp" here, which means that it is a real-time
> task in primary mode using the FPU in primary mode.

I probably don't have time for debugging for some days now, but if any 
of the code goes through sigreturn path, it might be a kernel bug that's 
fixed in 2.6.16.

-- hl