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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Tue, 26 Sep 2023 18:56:26 +0900
Message-ID: <CAK7LNASwcMf4utu238T6xtJwbnFHSvWntLenve4_KXShOJva6A@mail.gmail.com>
Subject: Re: [PATCH] modpost: Optimize symbol search from linear to binary search
To:     Joe Perches <joe@perches.com>
Cc:     Jack Brennen <jbrennen@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>, Tom Rix <trix@redhat.com>,
        linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
        llvm@lists.linux.dev, maskray@google.com, cleger@rivosinc.com,
        kernel-team@android.com
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On Tue, Sep 26, 2023 at 4:24=E2=80=AFPM Joe Perches <joe@perches.com> wrote=
:
>
> On Tue, 2023-09-26 at 15:46 +0900, Masahiro Yamada wrote:
> > On Tue, Sep 26, 2023 at 5:59=E2=80=AFAM Jack Brennen <jbrennen@google.c=
om> wrote:
> >
> > > +Elf_Sym *symsearch_find_nearest(struct elf_info *elf, Elf_Addr addr,
> > > +                               unsigned int secndx, bool allow_negat=
ive,
> > > +                               Elf_Addr min_distance)
> > > +{
> > > +       size_t hi =3D elf->symsearch->table_size;
> > > +       size_t lo =3D 0;
> > > +       struct syminfo *table =3D elf->symsearch->table;
> > > +       struct syminfo target;
> > > +
> > > +       target.addr =3D addr;
> > > +       target.section_index =3D secndx;
> > > +       target.symbol_index =3D ~0;  /* compares greater than any act=
ual index */
> > > +       while (hi > lo) {
> > > +               size_t mid =3D lo + (hi-lo)/2;   /* Avoids potential =
overflow */
> > > +
> > > +               if (syminfo_compare(&table[mid], &target) > 0)
> > > +                       hi =3D mid;
> > > +               else
> > > +                       lo =3D mid+1;
> >
> > My preference is "low =3D mid + 1" over "low =3D mid+1"
> >
> > Documentation/process/coding-style.rst suggests spaces
> > around binary operators.
> >
> > "
> > Use one space around (on each side of) most binary and ternary operator=
s,
> > such as any of these::
> >
> >         =3D  +  -  <  >  *  /  %  |  &  ^  <=3D  >=3D  =3D=3D  !=3D  ? =
 :
> > "
> >
> > I can see the corresponding line in the checkpatch tool:
> >
> > https://github.com/torvalds/linux/blob/v6.5/scripts/checkpatch.pl#L5330
> >
> >
> > I wonder why the checkpatch did not detect it.
> >
> > Maybe, Joe Perches may know the reason.
>
> checkpatch requires --strict to emit that message.
>


Ah, now I see it.  I learned a new thing today.


CHECK: spaces preferred around that '+' (ctx:VxV)
#466: FILE: scripts/mod/symsearch.c:172:
+ lo =3D mid+1;
          ^


--
Best Regards
Masahiro Yamada