Messages in this thread Patch in this message | | | Date | Thu, 10 May 2007 22:32:31 +0900 | From | Hirokazu Takata <> | Subject | Re: [PATCH 2.6.21] m32r: Fix switch_to macro to push/pop frame pointer if needed |
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From: Andrew Morton <akpm@linux-foundation.org> > On Thu, 10 May 2007 13:58:36 +0900 Hirokazu Takata <takata.hirokazu@renesas.com> wrote: > > > +#if defined(CONFIG_FRAME_POINTER) > > + || !defined(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER) > > hm, I didn't know that the preprocessor permitted that. > > I'll stick a \ in there to be safe. >
Oops! It was my mistake. Here is a revised patch, please replace the previous one.
Thanks,
-- Takata
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 <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: Hitoshi Yamamoto <hitoshiy@linux-m32r.org> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> --- arch/m32r/Kconfig | 4 ++++ include/asm-m32r/system.h | 11 +++++++++++ 2 files changed, 15 insertions(+), 0 deletions(-)
diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig index 9740d6b..c3bb8a7 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 99ee098..76a6255 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)), \ -- 1.5.1 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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