From: Hirokazu Takata Date: Fri, 11 May 2007 05:22:25 +0000 (-0700) Subject: m32r: fix switch_to macro to push/pop frame pointer if needed X-Git-Tag: v2.6.22-rc1~92 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=43c09ce7927912c7867617cba0a265beea38a154;p=pandora-kernel.git 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 --- Reading git-diff-tree failed