On Thu, 8 Dec 2016 13:50:11 +0300 "Kirill A. Shutemov" <kirill.shute...@linux.intel.com> wrote:
> On Wed, Dec 07, 2016 at 11:38:33PM -0500, Jérémy Lefaure wrote: > > When CONFIG_TRANSPARENT_HUGEPAGE is disabled, split_huge_pmd is a no-op > > stub. In such case, vma is unused and a compiler raises a warning: > > > > arch/x86/kernel/vm86_32.c: In function ‘mark_screen_rdonly’: > > arch/x86/kernel/vm86_32.c:180:26: warning: unused variable ‘vma’ > > [-Wunused-variable] > > struct vm_area_struct *vma = find_vma(mm, 0xA0000); > > ^~~ > > Adding __maybe_unused in the vma declaration fixes this warning. > > Hm. pmd_trans_huge() is zero if CONFIG_TRANSPARENT_HUGEPAGE is not set. > Compiler should get rid of whole block of code under the 'if'. > > Could you share your kernel config which triggers the warning? > And what compiler do you use? > After a `make allnoconfig`, I enable "Legacy VM86 support" and nothing else. I tested with 2 compilers, gcc 4.9.2 (on debian jessie) and gcc 6.2.1 (on archlinux). Actually, the compiler does not raise warnings on complete build (`make mrproper`, configuration and `make`) but only on partial build (`make arch/x86/kernel/vm86_32.o` or `touch arch/x86/kernel/vm86_32.c && make`). So maybe it is a compiler issue ? The solution you propose in your other email (adding "(void)__vma;" in the no-op split_huge_pmd) seems to fix the warnings on partial build. Thanks, Jérémy
