On Jun. 30, 2008, 19:22 +0300, Jeff Dike <[EMAIL PROTECTED]> wrote: > On Sun, Jun 29, 2008 at 10:32:43AM +0300, Benny Halevy wrote: >> Note that the crash happened with gcc 4.1.2 and it will get the >> -fno-unit-at-a-time flag with the proposed patch. >> >> That said, this option or the lack of it ought not to cause any >> runtime crashes. If it does, I'd feel much more comfortable to know >> exactly what the root cause is before deciding to use the flag to >> workaround^hide it. > > I agree. > > The constraints on [no-]unit-at-a-time that I see are: > i386 uses no-unit-at-a-time for pre-4.0 (not 4.3) > x86_64 uses unit-at-a-time always > > Uli reported a crash on x86_64 with gcc 4.1.2 with unit-at-a-time > Ingo reported a gcc internal error with gcc 4.3 with > no-unit-at-a-time > You are seeing extern inlines not resolved with gcc 4.3 with > no-unit-at-a-time > > I'm tempted to follow x86 on this, with the results that > extern inlines should be fine > Ingo's gcc crash should not reappear > Uli's crash may reappear > > If that crash does come back, I'd say we should just debug it. It's > likely UML implicitly relying on some gcc behavior anyway.
Agreed. > > This is the patch that I'm dropping into my tree: > > Index: linux-2.6.22/arch/um/Makefile-i386 > =================================================================== > --- linux-2.6.22.orig/arch/um/Makefile-i386 2008-05-29 11:21:25.000000000 > -0400 > +++ linux-2.6.22/arch/um/Makefile-i386 2008-06-30 12:20:01.000000000 > -0400 > @@ -32,4 +32,10 @@ cflags-y += $(call cc-option,-mpreferred > # an unresolved reference. > cflags-y += -ffreestanding > > +# Disable unit-at-a-time mode on pre-gcc-4.0 compilers, it makes gcc use > +# a lot more stack due to the lack of sharing of stacklots. Also, gcc > +# 4.3.0 needs -funit-at-a-time for extern inline functions. > +KBUILD_CFLAGS += $(shell if [ $(call cc-version) -lt 0403 ] ; then \ This isn't exactly aligned with the comment above. Should be -lt 0400, as in 22eecde2f9034764a3fd095eecfa3adfb8ec9a98? > + echo $(call cc-option,-fno-unit-at-a-time); fi ;) > + > KBUILD_CFLAGS += $(cflags-y) > Index: linux-2.6.22/arch/um/Makefile-x86_64 > =================================================================== > --- linux-2.6.22.orig/arch/um/Makefile-x86_64 2008-05-29 11:21:25.000000000 > -0400 > +++ linux-2.6.22/arch/um/Makefile-x86_64 2008-06-30 12:21:01.000000000 > -0400 > @@ -21,3 +21,6 @@ HEADER_ARCH := x86 > > LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64 > LINK-y += -m64 > + > +# Do unit-at-a-time unconditionally on x86_64, following the host > +KBUILD_CFLAGS += $(call cc-option,-funit-at-a-time) Hmm, arch/um/Makefile includes $(srctree)/$(ARCH_DIR)/Makefile-$(SUBARCH) before add -fno-unit-at-a-time to KBUILD_CFLAGS. Will this override the flag set first here? Benny > > Jeff > ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://sourceforge.net/services/buy/index.php _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
