From 43c09ce7927912c7867617cba0a265beea38a154 Mon Sep 17 00:00:00 2001 From: Hirokazu Takata Date: Thu, 10 May 2007 22:22:25 -0700 Subject: [PATCH] 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 > 4127272c38619c56f0c1aa01d01c7bd757db70a1 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 , 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: Hitoshi Yamamoto Signed-off-by: Hirokazu Takata Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/m32r/Kconfig | 4 ++++ include/asm-m32r/system.h | 11 +++++++++++ 2 files changed, 15 insertions(+) diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig index 9740d6b8ae11..c3bb8a755b00 100644 --- a/arch/m32r/Kconfig +++ b/arch/m32r/Kconfig @@ -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 diff --git a/include/asm-m32r/system.h b/include/asm-m32r/system.h index f62f5c9abba6..b291b2f72954 100644 --- a/include/asm-m32r/system.h +++ b/include/asm-m32r/system.h @@ -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)), \