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From: Sam R. <sa...@ra...> - 2009-07-17 20:28:58
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On Sat, Jun 27, 2009 at 04:13:04PM -0400, Steven Rostedt wrote: > > A change like this requires an ACK from Sam Ravnborg. > > -- Steve Overdue review... I do not know the gcc option so I cannot comment on theeffect of it. > > > > > diff --git a/Makefile b/Makefile > > index 2903e13..f73b139 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -524,6 +524,10 @@ else > > KBUILD_CFLAGS += -O2 > > endif > > > > +ifdef CONFIG_DISABLE_CROSSJUMP > > +KBUILD_CFLAGS += -fno-crossjumping > > +endif > > + > > include $(srctree)/arch/$(SRCARCH)/Makefile Why do we add this option _before_ we include the arch specific Makefile? If we do not want the arch specific Makefile to undo this then move it lower. Also please add a comment what the effect of the disabling is. There is no reason I should fire up info gcc to find out what -fno-crossjumping is about. > > > > ifneq ($(CONFIG_FRAME_WARN),0) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index 8da7467..f88e6b8 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -673,6 +673,13 @@ config FRAME_POINTER > > larger and slower, but it gives very useful debugging information > > in case of kernel bugs. (precise oopses/stacktraces/warnings) > > > > +config DISABLE_CROSSJUMP > > + bool "Disable cross-function jump optimization" > > + help > > + This build option disables cross-function jump optimization > > + (crossjumping) of gcc. Disabling crossjumping might increase > > + kernel binary size a little. So the above comment tells me that is I disable crossjumping I will increase the kernel image a little. That is by no means a good explanation. Please explain the potential advantage of disabling crossjumping. Sam |