On Thu, May 21, 2020 at 11:10:13AM -0700, Andrew Morton wrote: > 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. I can reporduce it with make W=1 ARCH=parisc CROSS_COMPILE=/opt/gcc-8.1.0-nolibc/hppa-linux/bin/hppa-linux- on both the v5.7-rc6 and linux-next. The only difference in the header names: --- build-master.log 2020-05-21 21:44:03.064168815 +0300 +++ build-next.log 2020-05-21 21:44:52.372330747 +0300 @@ -2,25 +2,26 @@ GEN Makefile CALL scripts/atomic/check-atomics.sh CC arch/parisc/kernel/asm-offsets.s -In file included from include/linux/mm.h:95, +In file included from include/linux/pgtable.h:6, + from include/linux/mm.h:31, from include/linux/pid_namespace.h:7, from include/linux/ptrace.h:10, from arch/parisc/kernel/asm-offsets.c:20: -include/asm-generic/pgtable.h: In function 'pte_clear_not_present_full': +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] pte_t old_pte; \ ^~~~~~~ arch/parisc/include/asm/pgtable.h:322:34: note: in expansion of macro 'set_pte_at' #define pte_clear(mm, addr, xp) set_pte_at(mm, addr, xp, __pte(0)) ^~~~~~~~~~ ... I think moving asm-generic/pgtable.h to linux/pgtable.h triggered the "new warning" notification. And the fix is obviously: >From 6de5f02d11fef8894836168c3e7bede05916d02d Mon Sep 17 00:00:00 2001 From: Mike Rapoport <rppt@xxxxxxxxxxxxx> Date: Thu, 21 May 2020 21:49:01 +0300 Subject: [PATCH] parisc: set_pte_at: remove unused old_pte variable. kbuild test robot complains about unused variable old_pte in set_pte_at() macro: 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)) Remove the old_pte variable. Reported-by: kbuild test robot <lkp@xxxxxxxxx> Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> --- arch/parisc/include/asm/pgtable.h | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h index 097d19007f2e..75cf84070fc9 100644 --- a/arch/parisc/include/asm/pgtable.h +++ b/arch/parisc/include/asm/pgtable.h @@ -93,10 +93,8 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr) #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);\ -- 2.26.2 -- Sincerely yours, Mike.
