• Hirokazu Takata's avatar
    m32r: fix switch_to macro to push/pop frame pointer if needed · 43c09ce7
    Hirokazu Takata authored
    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 --
     # 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
    Therefore, for the recent m32r kernel, we have to push/pop 'fp'
    (frame pointer) if CONFIG_FRAME_POINTER is defined or
    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>
Kconfig 9.5 KB