On Thu, 21 May 2020 17:30:52 +0800 kbuild test robot <lkp@xxxxxxxxx> wrote: > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master > head: fb57b1fabcb28f358901b2df90abd2b48abc1ca8 > commit: ef03574dee21524cbdbbf2af29fe06a62610570d [10668/10701] mm: introduce include/linux/pgtable.h > config: parisc-randconfig-r011-20200521 (attached as .config) > compiler: hppa-linux-gcc (GCC) 9.3.0 > reproduce: > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > git checkout ef03574dee21524cbdbbf2af29fe06a62610570d > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=parisc > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > > All warnings (new ones prefixed by >>, old ones prefixed by <<): > > In file included from include/linux/pgtable.h:6, > from include/linux/mm.h:95, > from include/linux/pid_namespace.h:7, > from include/linux/ptrace.h:10, > from arch/parisc/kernel/asm-offsets.c:20: > include/linux/pgtable.h: In function 'pte_clear_not_present_full': > arch/parisc/include/asm/pgtable.h:96:9: warning: variable 'old_pte' set but not used [-Wunused-but-set-variable] > 96 | pte_t old_pte; | ^~~~~~~ > arch/parisc/include/asm/pgtable.h:322:34: note: in expansion of macro 'set_pte_at' > 322 | #define pte_clear(mm, addr, xp) set_pte_at(mm, addr, xp, __pte(0)) > | ^~~~~~~~~~ > >> include/linux/pgtable.h:203:2: note: in expansion of macro 'pte_clear' > 203 | pte_clear(mm, address, ptep); > | ^~~~~~~~~ > include/linux/pgtable.h: In function '__ptep_modify_prot_commit': > arch/parisc/include/asm/pgtable.h:96:9: warning: variable 'old_pte' set but not used [-Wunused-but-set-variable] I can't reproduce this. And I can't see anything in -mm whcih would have triggered this warning. arch/parisc/include/asm/pgtable.h has #define set_pte_at(mm, addr, ptep, pteval) \ do { \ pte_t old_pte; \ unsigned long flags; \ spin_lock_irqsave(pgd_spinlock((mm)->pgd), flags);\ old_pte = *ptep; \ set_pte(ptep, pteval); \ purge_tlb_entries(mm, addr); \ spin_unlock_irqrestore(pgd_spinlock((mm)->pgd), flags);\ } while (0) and old_pte has been set-but-not-used for a long time. Obviously we can fix it, but I'm worried that parisc's set_pte_at() was previously unused and we've now done something to cause it to be used, so we're now running previously untested code.
