[PATCH 0/3] Add new ptrace request macros on PowerPC

[Anshuman Khandual]

On 04/29/2014 01:52 PM, Michael Neuling wrote:
> That's not what that patch does. It shouldn't make any user visible changes
> to DSCR or PPR.

It may not when it runs uninterrupted but after the tracee process has stopped,
thread.dscr reflects the default DSCR value as mentioned before. This can be
proved by changing the "dscr_default" value in arch/powerpc/sysfs.c file.

> 
> Over syscall PPR and DSCR may change. Depending on your test case, that may
> be your problem.

I would guess when the tracee process stops for ptrace analysis, tm_reclaim or
tm_recheckpoint path might be crossed which is causing this dscr_default value
to go into thread_struct.