Warning is not triggered in next. Looks like this patch is unnecessary. Thanks, Nathan Huckleberry
On Wed, Jul 3, 2019 at 4:23 AM Mark Rutland <[email protected]> wrote: > > On Tue, Jul 02, 2019 at 04:41:35PM -0700, Nathan Huckleberry wrote: > > When analyzed with the clang static analyzer the > > following warning occurs > > > > line 251, column 2 > > Value stored to 'old_pte' is never read > > > > This warning is repeated every time pgtable.h is > > included by another file and produces ~3500 > > extra warnings. > > > > Moving old_pte into preprocessor guard. > > > > Cc: [email protected] > > Signed-off-by: Nathan Huckleberry <[email protected]> > > --- > > Changes from v1 -> v2 > > * Added scope to avoid [-Wdeclaration-after-statement] > > arch/arm64/include/asm/pgtable.h | 27 ++++++++++++++++----------- > > 1 file changed, 16 insertions(+), 11 deletions(-) > > As Will asked, does this also trigger in linux-next? > > I rewrote this code to avoid to only perform the READ_ONCE() when we'd > use the value, and IIUC that may be sufficient to avoid the warning: > > https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?h=for-next/core&id=9b604722059039a1a3ff69fb8dfd024264046024 > > Thanks, > Mark. > > > > > diff --git a/arch/arm64/include/asm/pgtable.h > > b/arch/arm64/include/asm/pgtable.h > > index fca26759081a..12b7f08db40d 100644 > > --- a/arch/arm64/include/asm/pgtable.h > > +++ b/arch/arm64/include/asm/pgtable.h > > @@ -238,8 +238,6 @@ extern void __sync_icache_dcache(pte_t pteval); > > static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, > > pte_t *ptep, pte_t pte) > > { > > - pte_t old_pte; > > - > > if (pte_present(pte) && pte_user_exec(pte) && !pte_special(pte)) > > __sync_icache_dcache(pte); > > > > @@ -248,16 +246,23 @@ static inline void set_pte_at(struct mm_struct *mm, > > unsigned long addr, > > * hardware updates of the pte (ptep_set_access_flags safely changes > > * valid ptes without going through an invalid entry). > > */ > > - old_pte = READ_ONCE(*ptep); > > - if (IS_ENABLED(CONFIG_DEBUG_VM) && pte_valid(old_pte) && > > pte_valid(pte) && > > - (mm == current->active_mm || atomic_read(&mm->mm_users) > 1)) { > > - VM_WARN_ONCE(!pte_young(pte), > > - "%s: racy access flag clearing: 0x%016llx -> > > 0x%016llx", > > - __func__, pte_val(old_pte), pte_val(pte)); > > - VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte), > > - "%s: racy dirty state clearing: 0x%016llx -> > > 0x%016llx", > > - __func__, pte_val(old_pte), pte_val(pte)); > > + #if IS_ENABLED(CONFIG_DEBUG_VM) > > + { > > + pte_t old_pte; > > + > > + old_pte = READ_ONCE(*ptep); > > + if (pte_valid(old_pte) && pte_valid(pte) && > > + (mm == current->active_mm || > > + atomic_read(&mm->mm_users) > 1)) { > > + VM_WARN_ONCE(!pte_young(pte), > > + "%s: racy access flag clearing: > > 0x%016llx -> 0x%016llx", > > + __func__, pte_val(old_pte), > > pte_val(pte)); > > + VM_WARN_ONCE(pte_write(old_pte) && !pte_dirty(pte), > > + "%s: racy dirty state clearing: > > 0x%016llx -> 0x%016llx", > > + __func__, pte_val(old_pte), > > pte_val(pte)); > > + } > > } > > + #endif > > > > set_pte(ptep, pte); > > } > > -- > > 2.22.0.410.gd8fdbe21b5-goog > > > > > > _______________________________________________ > > linux-arm-kernel mailing list > > [email protected] > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
