Re: 2.6.39-rc6-mmotm0506 and -next - __kfree_rcu breaks third-partykernel code

[Randy Dunlap]

On 05/09/11 09:56, Valdis.Kletnieks@xxxxxx wrote:
> On Mon, 09 May 2011 09:17:57 PDT, Randy Dunlap said:
> 
>> I'd be happy to see a simple fix, but we don't generally support building
>> external modules without using the kernel kbuild infrastructure AFAIK --
>> and when I add a Makefile along with your kernconf.c file, it builds successfully
>> on mmotm-2011-0506-1639.
> 
> And in fact the module *does* use the Makefile stuff for the actual build - it
> was just the installer's "am I looking at a sane 2.6 tree" sanity check that
> bombed. So I go looking for what special sauce the Makefile adds to make it
> work, and....
> 
> OK, *now* I'm confused.  The magic sauce appears to be "-Os". Adding that makes
> the compile work.  And for no obvious reason - there's something in there that
> causes indigestion, but only if the optimizer isn't invoked.

You can disable that by disabling:
CONFIG_CC_OPTIMIZE_FOR_SIZE=y

> *WTF*?

I dunno either.

>  LANG=C ./kern.sh 
> cat > /tmp/kernconf.c <<EOF
> #include <linux/version.h>
> #include <linux/utsname.h>
> EOF
> + cat
> 
> kern="/lib/modules/2.6.39-rc6-mmotm0506/"
> + kern=/lib/modules/2.6.39-rc6-mmotm0506/
> cc -D__KERNEL__ -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.6.0/include -I${kern}/build/include -I$kern/arch/x86/include/generated -include ${kern}/build/include/generated/autoconf.h -I${kern}/build/arch/x86/include -I${kern}/include/generated -Os -c /tmp/kernconf.c
> + cc -D__KERNEL__ -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.6.0/include -I/lib/modules/2.6.39-rc6-mmotm0506//build/include -I/lib/modules/2.6.39-rc6-mmotm0506//arch/x86/include/generated -include /lib/modules/2.6.39-rc6-mmotm0506//build/include/generated/autoconf.h -I/lib/modules/2.6.39-rc6-mmotm0506//build/arch/x86/include -I/lib/modules/2.6.39-rc6-mmotm0506//include/generated -Os -c /tmp/kernconf.c
> cc -D__KERNEL__ -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.6.0/include -I${kern}/build/include -I$kern/arch/x86/include/generated -include ${kern}/build/include/generated/autoconf.h -I${kern}/build/arch/x86/include -I${kern}/include/generated -c /tmp/kernconf.c
> + cc -D__KERNEL__ -nostdinc -isystem /usr/lib/gcc/x86_64-redhat-linux/4.6.0/include -I/lib/modules/2.6.39-rc6-mmotm0506//build/include -I/lib/modules/2.6.39-rc6-mmotm0506//arch/x86/include/generated -include /lib/modules/2.6.39-rc6-mmotm0506//build/include/generated/autoconf.h -I/lib/modules/2.6.39-rc6-mmotm0506//build/arch/x86/include -I/lib/modules/2.6.39-rc6-mmotm0506//include/generated -c /tmp/kernconf.c
> In file included from /lib/modules/2.6.39-rc6-mmotm0506//build/include/linux/sem.h:81:0,
>                  from /lib/modules/2.6.39-rc6-mmotm0506//build/include/linux/sched.h:72,
>                  from /lib/modules/2.6.39-rc6-mmotm0506//build/include/linux/utsname.h:35,
>                  from /tmp/kernconf.c:2:
> /lib/modules/2.6.39-rc6-mmotm0506//build/include/linux/rcupdate.h: In function '__kfree_rcu':
> /lib/modules/2.6.39-rc6-mmotm0506//build/include/linux/rcupdate.h:822:2: error: size of unnamed array is negative
> 
> rm /tmp/kernconf.c
> + rm /tmp/kernconf.c

rcupdate.h should #include <linux/kernel.h>, but I don't think that will fix this problem.

-- 
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/