linux-kernel - Re: [PATCHv2] powerpc: mm: radix_tlb: rearrange the if-else block

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Date:   Fri, 28 Jan 2022 14:07:00 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     "nathan@...nel.org" <nathan@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCHv2] powerpc: mm: radix_tlb: rearrange the if-else block

On Fri, 28 Jan 2022 at 11:14, Christophe Leroy
<christophe.leroy@...roup.eu> wrote:
>
>
>
> Le 28/01/2022 à 11:08, Anders Roxell a écrit :
> > Clang warns:
> >
> > arch/powerpc/mm/book3s64/radix_tlb.c:1191:23: error: variable 'hstart' is uninitialized when used here [-Werror,-Wuninitialized]
> >                                  __tlbiel_va_range(hstart, hend, pid,
> >                                                    ^~~~~~
> > arch/powerpc/mm/book3s64/radix_tlb.c:1175:23: note: initialize the variable 'hstart' to silence this warning
> >                  unsigned long hstart, hend;
> >                                      ^
> >                                       = 0
> > arch/powerpc/mm/book3s64/radix_tlb.c:1191:31: error: variable 'hend' is uninitialized when used here [-Werror,-Wuninitialized]
> >                                  __tlbiel_va_range(hstart, hend, pid,
> >                                                            ^~~~
> > arch/powerpc/mm/book3s64/radix_tlb.c:1175:29: note: initialize the variable 'hend' to silence this warning
> >                  unsigned long hstart, hend;
> >                                            ^
> >                                             = 0
> > 2 errors generated.
> >
> > Rework the 'if (IS_ENABLE(CONFIG_TRANSPARENT_HUGEPAGE))' so hstart/hend
> > always gets initialized, this will silence the warnings. That will also
> > simplify the 'else' path. Clang is getting confused with these warnings,
> > but the warnings is a false-positive.
> >
> > Suggested-by: Arnd Bergmann <arnd@...db.de>
> > Suggested-by: Nathan Chancellor <nathan@...nel.org>
> > Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
> > ---
> >   arch/powerpc/mm/book3s64/radix_tlb.c | 9 +++------
> >   1 file changed, 3 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
> > index 7724af19ed7e..7d65965a0688 100644
> > --- a/arch/powerpc/mm/book3s64/radix_tlb.c
> > +++ b/arch/powerpc/mm/book3s64/radix_tlb.c
> > @@ -1174,12 +1174,9 @@ static inline void __radix__flush_tlb_range(struct mm_struct *mm,
> >               bool hflush = false;
>
> You should then remove the default initialisation of hflush to false
> which has become pointless.
>
> With that fixed,
>
> Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

Thank you for the review.
I will send a v3 shortly with that fixed.

Cheers,
Anders