percpu: fix DEBUG_PREEMPT per_cpu checking

2.6.25-rc1 percpu changes broke CONFIG_DEBUG_PREEMPT's per_cpu checking
on several architectures.  On s390, sparc64 and x86 it's been weakened to
not checking at all; whereas on powerpc64 it's become too strict, issuing
warnings from __raw_get_cpu_var in io_schedule and init_timer for example.

Fix this by weakening powerpc's __my_cpu_offset to use the non-checking
local_paca instead of get_paca (which itself contains such a check);
and strengthening the generic my_cpu_offset to go the old slow way via
smp_processor_id when CONFIG_DEBUG_PREEMPT (debug_smp_processor_id is
where all the knowledge of what's correct when lives).

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Reviewed-by: Mike Travis <travis@sgi.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 4b8d31cda1a0..b0e63c672ebd 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -32,6 +32,8 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
  */
 #ifndef __my_cpu_offset
 #define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
+#endif
+#ifdef CONFIG_DEBUG_PREEMPT
 #define my_cpu_offset per_cpu_offset(smp_processor_id())
 #else
 #define my_cpu_offset __my_cpu_offset