Messages in this thread | | | From | Barry Song <> | Date | Tue, 19 Mar 2024 15:16:08 +1300 | Subject | Re: [PATCH v2] xtensa: remove redundant flush_dcache_page and ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE macros |
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On Tue, Mar 19, 2024 at 3:12 PM Max Filippov <jcmvbkbc@gmail.com> wrote: > > On Mon, Mar 18, 2024 at 6:27 PM Barry Song <21cnbao@gmail.com> wrote: > > On Tue, Mar 19, 2024 at 2:09 PM Barry Song <21cnbao@gmail.com> wrote: > > > From: Barry Song <v-songbaohua@oppo.com> > > > > > > xtensa's flush_dcache_page() can be a no-op sometimes. There is a > > > generic implementation for this case in include/asm-generic/ > > > cacheflush.h. > > > #ifndef ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE > > > static inline void flush_dcache_page(struct page *page) > > > { > > > } > > > > > > #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0 > > > #endif > > > > > > So remove the superfluous flush_dcache_page() definition, which also > > > helps silence potential build warnings complaining the page variable > > > passed to flush_dcache_page() is not used. > > > > > > In file included from crypto/scompress.c:12: > > > include/crypto/scatterwalk.h: In function 'scatterwalk_pagedone': > > > include/crypto/scatterwalk.h:76:30: warning: variable 'page' set but not used [-Wunused-but-set-variable] > > > 76 | struct page *page; > > > | ^~~~ > > > crypto/scompress.c: In function 'scomp_acomp_comp_decomp': > > > >> crypto/scompress.c:174:38: warning: unused variable 'dst_page' [-Wunused-variable] > > > 174 | struct page *dst_page = sg_page(req->dst); > > > | > > > > > > The issue was originally reported on LoongArch by kernel test > > > robot (Huacai fixed it on LoongArch), then reported by Guenter > > > and me on xtensa. > > I wonder why this warning is considered useful in the first place?
Guenter reported it as an error not a warning "
Error log: crypto/scompress.c: In function 'scomp_acomp_comp_decomp': crypto/scompress.c:174:38: error: unused variable 'dst_page'"
is it because xtensa's toolchain is different with others?
> If I'm missing something and it's indeed useful, should there be a > rule in the Documentation/process/coding-style.rst saying that > function-like macros should evaluate all their arguments? > > > > This patch also removes lots of redundant macros which have > > > been defined by asm-generic/cacheflush.h. > > > > > > Cc: Huacai Chen <chenhuacai@loongson.cn> > > > Cc: Herbert Xu <herbert@gondor.apana.org.au> > > > Reported-by: kernel test robot <lkp@intel.com> > > > Closes: https://lore.kernel.org/oe-kbuild-all/202403091614.NeUw5zcv-lkp@intel.com/ > > > Reported-by: Barry Song <v-songbaohua@oppo.com> > > > Closes: https://lore.kernel.org/all/CAGsJ_4yDk1+axbte7FKQEwD7X2oxUCFrEc9M5YOS1BobfDFXPA@mail.gmail.com/ > > > Reported-by: Guenter Roeck <linux@roeck-us.net> > > > > Hi Guenter, > > I am not a xtensa guy, so I will need your help for a full test. if > > turns out it is a too big(ambitious) > > fix, a minimal fix might be: > > > > diff --git a/arch/xtensa/include/asm/cacheflush.h > > b/arch/xtensa/include/asm/cacheflush.h > > index 38bcecb0e457..fdc692cf2b78 100644 > > --- a/arch/xtensa/include/asm/cacheflush.h > > +++ b/arch/xtensa/include/asm/cacheflush.h > > @@ -145,7 +145,7 @@ void local_flush_cache_page(struct vm_area_struct *vma, > > #define flush_cache_vunmap(start,end) do { } while (0) > > > > #define ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE 0 > > -#define flush_dcache_page(page) do { } while (0) > > +#define flush_dcache_page(page) do { > > (void)(page); } while (0) > > This looks like a good fix, IMO better than adding __maybe_unused > to the variables reported in the warnings.
i don't like adding __maybe_unused either as it is not the fault of the drivers calling flush_dcache_page().
> > -- > Thanks. > -- Max
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