Commit 43c09ce7 authored by Hirokazu Takata's avatar Hirokazu Takata Committed by Linus Torvalds
Browse files

m32r: fix switch_to macro to push/pop frame pointer if needed

This patch fixes a rarely-happened but severe scheduling problem of
the recent m32r kernel of 2.6.17-rc3 or later.

In the following previous m32r patch, the switch_to macro was
modified not to do unnecessary push/pop operations for tuning.
> [PATCH] m32r: update switch_to macro for tuning
> 4127272c



In this modification, only 'lr' and 'sp' registers are push/pop'ed,
assuming that the m32r kernel is always compiled with
-fomit-frame-pointer option.

However, in 2.6 kernel, kernel/sched.c is irregularly compiled
with -fno-omit-frame-pointer if CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER
is not defined.

 -- kernel/Makefile --
   :
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
 # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
 # needed for x86 only.  Why this used to be enabled for all architectures is beyond
 # me.  I suspect most platforms don't need this, but until we know that for sure
 # I turn this off for IA-64 only.  Andreas Schwab says it's also needed on m68k
 # to get a correct value for the wait-channel (WCHAN in ps). --davidm
 CFLAGS_sched.o := $(PROFILING) -fno-omit-frame-pointer
 endif
   :
 ---

Therefore, for the recent m32r kernel, we have to push/pop 'fp'
(frame pointer) if CONFIG_FRAME_POINTER is defined or
CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER is not defined.
Signed-off-by: default avatarHitoshi Yamamoto <hitoshiy@linux-m32r.org>
Signed-off-by: default avatarHirokazu Takata <takata@linux-m32r.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 44316634
......@@ -241,6 +241,10 @@ config GENERIC_CALIBRATE_DELAY
bool
default y
config SCHED_NO_NO_OMIT_FRAME_POINTER
bool
default y
config PREEMPT
bool "Preemptible Kernel"
help
......
......@@ -21,12 +21,22 @@
* `next' and `prev' should be struct task_struct, but it isn't always defined
*/
#if defined(CONFIG_FRAME_POINTER) || \
!defined(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER)
#define M32R_PUSH_FP " push fp\n"
#define M32R_POP_FP " pop fp\n"
#else
#define M32R_PUSH_FP ""
#define M32R_POP_FP ""
#endif
#define switch_to(prev, next, last) do { \
__asm__ __volatile__ ( \
" seth lr, #high(1f) \n" \
" or3 lr, lr, #low(1f) \n" \
" st lr, @%4 ; store old LR \n" \
" ld lr, @%5 ; load new LR \n" \
M32R_PUSH_FP \
" st sp, @%2 ; store old SP \n" \
" ld sp, @%3 ; load new SP \n" \
" push %1 ; store `prev' on new stack \n" \
......@@ -34,6 +44,7 @@
" .fillinsn \n" \
"1: \n" \
" pop %0 ; restore `__last' from new stack \n" \
M32R_POP_FP \
: "=r" (last) \
: "0" (prev), \
"r" (&(prev->thread.sp)), "r" (&(next->thread.sp)), \
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment