[POWERPC] ppc64: support CONFIG_DEBUG_PREEMPT

Add CONFIG_DEBUG_PREEMPT support to ppc64: it was useful for testing
get_paca() preemption.  Cheat a little, just use debug_smp_processor_id()
in the debug version of get_paca(): it contains all the right checks and
reporting, though get_paca() doesn't really use smp_processor_id().

Use local_paca for what might have been called __raw_get_paca().
Silence harmless warnings from io.h and lparcfg.c with local_paca -
it is okay for iseries_lparcfg_data to be referencing shared_proc
with preemption enabled: all cpus should show the same value for
shared_proc.

Why do other architectures need TRACE_IRQFLAGS_SUPPORT for DEBUG_PREEMPT?
I don't know, ppc64 appears to get along fine without it.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 50a94eee4d92..51e2fd0d851c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -167,7 +167,7 @@ config SLUB_DEBUG_ON
 
 config DEBUG_PREEMPT
         bool "Debug preemptible kernel"
-        depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
+        depends on DEBUG_KERNEL && PREEMPT && (TRACE_IRQFLAGS_SUPPORT || PPC64)
         default y
         help
           If you say Y here then the kernel will use a debug variant of the