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From:   Masahiro Yamada <yamada.masahiro@socionext.com>
Date:   Mon, 25 Mar 2019 15:04:01 +0900
Message-ID: <CAK7LNATJMtDpu9vRcZ+EZxRw9LSfNihCrNi_o0JKLqP-PjcOHg@mail.gmail.com>
Subject: Re: [PATCH] compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     linux-arch <linux-arch@vger.kernel.org>,
        linux-s390 <linux-s390@vger.kernel.org>,
        Dave Hansen <dave@sr71.net>,
        Michael Ellerman <mpe@ellerman.id.au>, X86 ML <x86@kernel.org>,
        linux-mips@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Paul Burton <paul.burton@mips.com>,
        Ingo Molnar <mingo@redhat.com>,
        linux-mtd <linux-mtd@lists.infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Arnd,


On Wed, Mar 20, 2019 at 10:05 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Wed, Mar 20, 2019 at 11:19 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> > On Wed, Mar 20, 2019 at 6:39 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > >
> > > On Wed, Mar 20, 2019 at 7:41 AM Masahiro Yamada
> > > <yamada.masahiro@socionext.com> wrote:
> > >
> > > > It is unclear to me how to fix it.
> > > > That's why I ended up with "depends on !MIPS".
> > > >
> > > >
> > > >   MODPOST vmlinux.o
> > > > arch/mips/mm/sc-mips.o: In function `mips_sc_prefetch_enable.part.2':
> > > > sc-mips.c:(.text+0x98): undefined reference to `mips_gcr_base'
> > > > sc-mips.c:(.text+0x9c): undefined reference to `mips_gcr_base'
> > > > sc-mips.c:(.text+0xbc): undefined reference to `mips_gcr_base'
> > > > sc-mips.c:(.text+0xc8): undefined reference to `mips_gcr_base'
> > > > sc-mips.c:(.text+0xdc): undefined reference to `mips_gcr_base'
> > > > arch/mips/mm/sc-mips.o:sc-mips.c:(.text.unlikely+0x44): more undefined
> > > > references to `mips_gcr_base'
> > > >
> > > >
> > > > Perhaps, MIPS folks may know how to fix it.
> > >
> > > I would guess like this:
> > >
> > > diff --git a/arch/mips/include/asm/mips-cm.h b/arch/mips/include/asm/mips-cm.h
> > > index 8bc5df49b0e1..a27483fedb7d 100644
> > > --- a/arch/mips/include/asm/mips-cm.h
> > > +++ b/arch/mips/include/asm/mips-cm.h
> > > @@ -79,7 +79,7 @@ static inline int mips_cm_probe(void)
> > >   *
> > >   * Returns true if a CM is present in the system, else false.
> > >   */
> > > -static inline bool mips_cm_present(void)
> > > +static __always_inline bool mips_cm_present(void)
> > >  {
> > >  #ifdef CONFIG_MIPS_CM
> > >         return mips_gcr_base != NULL;
> > > @@ -93,7 +93,7 @@ static inline bool mips_cm_present(void)
> > >   *
> > >   * Returns true if the system implements an L2-only sync region, else false.
> > >   */
> > > -static inline bool mips_cm_has_l2sync(void)
> > > +static __always_inline bool mips_cm_has_l2sync(void)
> > >  {
> > >  #ifdef CONFIG_MIPS_CM
> > >         return mips_cm_l2sync_base != NULL;
> > >
> >
> >
> > Thanks, I applied the above, but I still see
> >  undefined reference to `mips_gcr_base'
> >
> >
> > I attached .config to produce this error.
> >
> > I use prebuilt mips-linux-gcc from
> > https://mirrors.edge.kernel.org/pub/tools/crosstool/files/bin/x86_64/8.1.0/
>
> I got to this patch experimentally, it fixes the problem for me:
>
> diff --git a/arch/mips/mm/sc-mips.c b/arch/mips/mm/sc-mips.c
> index 394673991bab..d70d02da038b 100644
> --- a/arch/mips/mm/sc-mips.c
> +++ b/arch/mips/mm/sc-mips.c
> @@ -181,7 +181,7 @@ static int __init mips_sc_probe_cm3(void)
>         return 0;
>  }
>
> -static inline int __init mips_sc_probe(void)
> +static __always_inline int __init mips_sc_probe(void)
>  {
>         struct cpuinfo_mips *c = &current_cpu_data;
>         unsigned int config1, config2;
> diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h
> index 830c93a010c3..186c28463bf3 100644
> --- a/arch/mips/include/asm/bitops.h
> +++ b/arch/mips/include/asm/bitops.h
> @@ -548,7 +548,7 @@ static inline unsigned long __fls(unsigned long word)
>   * Returns 0..SZLONG-1
>   * Undefined if no bit exists, so code should check against 0 first.
>   */
> -static inline unsigned long __ffs(unsigned long word)
> +static __always_inline unsigned long __ffs(unsigned long word)
>  {
>         return __fls(word & -word);
>  }
>
>
> It does look like a gcc bug though, as at least some of the references
> are from a function that got split out from an inlined function but that
> has no remaining call sites.
>
>        Arnd


I applied it, but
"undefined reference to `mips_gcr_base'" still remains.


Then, I got a solution. This is it:

diff --git a/arch/mips/include/asm/bitops.h b/arch/mips/include/asm/bitops.h
index 830c93a..6a26ead 100644
--- a/arch/mips/include/asm/bitops.h
+++ b/arch/mips/include/asm/bitops.h
@@ -482,7 +482,7 @@ static inline void __clear_bit_unlock(unsigned
long nr, volatile unsigned long *
  * Return the bit position (0..63) of the most significant 1 bit in a word
  * Returns -1 if no 1 bit exists
  */
-static inline unsigned long __fls(unsigned long word)
+static __always_inline unsigned long __fls(unsigned long word)
 {
        int num;


LEROY Christophe provided me a tip
to find out the cause of the error.

-Winline pin-points which function
was not inlined despite of its inline marker.


$ make -j8  ARCH=mips CROSS_COMPILE=mips-linux- KCFLAGS=-Winline
arch/mips/mm/sc-mips.o
  CC      scripts/mod/devicetable-offsets.s
  CC      scripts/mod/empty.o
  MKELF   scripts/mod/elfconfig.h
  HOSTCC  scripts/mod/modpost.o
  HOSTCC  scripts/mod/sumversion.o
  HOSTCC  scripts/mod/file2alias.o
  HOSTLD  scripts/mod/modpost
  CC      kernel/bounds.s
  CALL    scripts/atomic/check-atomics.sh
  CC      arch/mips/kernel/asm-offsets.s
  CALL    scripts/checksyscalls.sh
<stdin>:1478:2: warning: #warning syscall pidfd_send_signal not
implemented [-Wcpp]
<stdin>:1481:2: warning: #warning syscall io_uring_setup not implemented [-Wcpp]
<stdin>:1484:2: warning: #warning syscall io_uring_enter not implemented [-Wcpp]
<stdin>:1487:2: warning: #warning syscall io_uring_register not
implemented [-Wcpp]
  CC      arch/mips/mm/sc-mips.o
In file included from ./include/linux/bitops.h:19,
                 from ./include/linux/kernel.h:12,
                 from arch/mips/mm/sc-mips.c:6:
./arch/mips/include/asm/bitops.h: In function 'mips_sc_init':
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~
./arch/mips/include/asm/bitops.h:485:29: warning: inlining failed in
call to '__fls': call is unlikely and code size would grow [-Winline]
 static inline unsigned long __fls(unsigned long word)
                             ^~~~~
./arch/mips/include/asm/bitops.h:553:9: note: called from here
  return __fls(word & -word);
         ^~~~~~~~~~~~~~~~~~~


-- 
Best Regards
Masahiro Yamada