From: Yury Norov <yury.norov@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Rikard Falkeborn <rikard.falkeborn@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
linux-m68k <linux-m68k@lists.linux-m68k.org>,
Linux-Arch <linux-arch@vger.kernel.org>,
Linux-SH <linux-sh@vger.kernel.org>,
Alexey Klimov <aklimov@redhat.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Arnd Bergmann <arnd@arndb.de>, David Sterba <dsterba@suse.com>,
Dennis Zhou <dennis@kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Jianpeng Ma <jianpeng.ma@intel.com>,
Joe Perches <joe@perches.com>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Rich Felker <dalias@libc.org>,
Stefano Brivio <sbrivio@redhat.com>,
Wei Yang <richard.weiyang@linux.alibaba.com>,
Wolfram Sang <wsa+renesas@sang-engineering.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>
Subject: Re: [PATCH 11/12] tools: sync lib/find_bit implementation
Date: Mon, 10 May 2021 10:21:26 -0700 [thread overview]
Message-ID: <YJlravuhJLlWaqjs@yury-ThinkPad> (raw)
In-Reply-To: <CAHp75Vea0Y_LfWC7LNDoDZqO4t+SVHV5HZMzErfyMPoBAjjk1g@mail.gmail.com>
On Mon, May 10, 2021 at 06:44:44PM +0300, Andy Shevchenko wrote:
> +Cc: Rikard
>
> On Mon, May 10, 2021 at 6:31 PM Tetsuo Handa
> <penguin-kernel@i-love.sakura.ne.jp> wrote:
> >
> > Commit eaae7841ba83bb42 ("tools: sync lib/find_bit implementation") broke
> > build of 5.13-rc1 using gcc (GCC) 8.3.1 20190311 (Red Hat 8.3.1-3).
> >
> > DESCEND objtool
> > CC /usr/src/linux/tools/objtool/exec-cmd.o
> > CC /usr/src/linux/tools/objtool/help.o
> > CC /usr/src/linux/tools/objtool/pager.o
> > CC /usr/src/linux/tools/objtool/parse-options.o
> > CC /usr/src/linux/tools/objtool/run-command.o
> > CC /usr/src/linux/tools/objtool/sigchain.o
> > CC /usr/src/linux/tools/objtool/subcmd-config.o
> > LD /usr/src/linux/tools/objtool/libsubcmd-in.o
> > AR /usr/src/linux/tools/objtool/libsubcmd.a
> > CC /usr/src/linux/tools/objtool/arch/x86/special.o
> > In file included from /usr/src/linux/tools/include/linux/kernel.h:8:0,
> > from /usr/src/linux/tools/include/linux/list.h:7,
> > from /usr/src/linux/tools/objtool/include/objtool/arch.h:10,
> > from /usr/src/linux/tools/objtool/include/objtool/check.h:11,
> > from /usr/src/linux/tools/objtool/include/objtool/special.h:10,
> > from arch/x86/special.c:4:
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_bit':
> > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO'
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:32:17: note: in expansion of macro 'GENMASK'
> > val = *addr & GENMASK(size - 1, offset);
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '<anonymous>' width not an integer constant
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO'
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:32:17: note: in expansion of macro 'GENMASK'
> > val = *addr & GENMASK(size - 1, offset);
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_and_bit':
> > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO'
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:62:27: note: in expansion of macro 'GENMASK'
> > val = *addr1 & *addr2 & GENMASK(size - 1, offset);
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '<anonymous>' width not an integer constant
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO'
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:62:27: note: in expansion of macro 'GENMASK'
> > val = *addr1 & *addr2 & GENMASK(size - 1, offset);
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h: In function 'find_next_zero_bit':
> > /usr/src/linux/tools/include/linux/bits.h:24:21: error: first argument to '__builtin_choose_expr' not a constant
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:62: note: in definition of macro 'BUILD_BUG_ON_ZERO'
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:90:18: note: in expansion of macro 'GENMASK'
> > val = *addr | ~GENMASK(size - 1, offset);
> > ^
> > /usr/src/linux/tools/include/linux/build_bug.h:16:51: error: bit-field '<anonymous>' width not an integer constant
> > #define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:24:3: note: in expansion of macro 'BUILD_BUG_ON_ZERO'
> > (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > ^
> > /usr/src/linux/tools/include/linux/bits.h:38:3: note: in expansion of macro 'GENMASK_INPUT_CHECK'
> > (GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
> > ^
> > /usr/src/linux/tools/include/asm-generic/bitops/find.h:90:18: note: in expansion of macro 'GENMASK'
> > val = *addr | ~GENMASK(size - 1, offset);
> > ^
> > make[5]: *** [/usr/src/linux/tools/objtool/arch/x86/special.o] Error 1
> > make[4]: *** [arch/x86] Error 2
> > make[3]: *** [/usr/src/linux/tools/objtool/objtool-in.o] Error 2
> > make[2]: *** [objtool] Error 2
> > make[1]: *** [tools/objtool] Error 2
> > make: *** [__sub-make] Error 2
> >
> >
> > Applying below diff seems to solve the build failure.
> >
> It will desynchronize this implementation with the mother's one (i.e.
> in bits.h).
>
> > Do we need to use BUILD_BUG_ON_ZERO() here?
>
> Rikard?
>
> >
> > diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h
> > index 7f475d59a097..0aba9294f29d 100644
> > --- a/tools/include/linux/bits.h
> > +++ b/tools/include/linux/bits.h
> > @@ -21,8 +21,7 @@
> > #if !defined(__ASSEMBLY__)
> > #include <linux/build_bug.h>
> > #define GENMASK_INPUT_CHECK(h, l) \
> > - (BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> > - __builtin_constant_p((l) > (h)), (l) > (h), 0)))
> > + ({ BUILD_BUG_ON(__builtin_constant_p((l) > (h)) && ((l) > (h))); 0; })
> > #else
> > /*
> > * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
As Andy said, we need to sync tools/GENMASK_INPUT_CHECK() with the
kernel version, and if I do this, I have many build failures:
https://pastebin.com/Fan1VLVF
Maybe in this case we should use __GENMASK() to bypass GENMASK_INPUT_CHECK()...
I'll check everything carefully this evening.
> > Also, why the fast path of find_*_bit() functions does not check
> > __builtin_constant_p(offset) as well as small_const_nbits(size), for the fast
> > path fails to catch BUILD_BUG_ON_ZERO() when offset argument is not a constant.
>
> How would this help anything?
>
> If you ask a bit from a bitmap behind the size, what do you expect to get?
>
> And I'm a bit lost here, because I can't imagine the offset being
> constant along with a size of bitmap. What do we want to achieve by
> this? Any examples to better understand the case?
If offset is constant, the existing fast path optimization would work
even better, without any modifications. (Not sure there's an example of
it in the existing codebase.) But even if the offset is not constant,
fast path works quite well - it saves ~1K of .text and improves on
performance:
https://lore.kernel.org/linux-m68k/20210321215457.588554-10-yury.norov@gmail.com/
We don't need to disable the optimization for non-constant offsets,
for sure. If asserts in GENMASK() break build, we should use __GENMASK().
Thanks,
Yury
next prev parent reply other threads:[~2021-05-10 17:21 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-01 0:31 [PATCH v6 00/12] lib/find_bit: fast path for small bitmaps Yury Norov
2021-04-01 0:31 ` [PATCH 01/12] tools: disable -Wno-type-limits Yury Norov
2021-04-01 0:31 ` [PATCH 02/12] tools: bitmap: sync function declarations with the kernel Yury Norov
2021-04-01 0:31 ` [PATCH 03/12] tools: sync BITMAP_LAST_WORD_MASK() macro " Yury Norov
2021-04-01 0:31 ` [PATCH 04/12] arch: rearrange headers inclusion order in asm/bitops for m68k and sh Yury Norov
2021-04-01 0:31 ` [PATCH 05/12] lib: extend the scope of small_const_nbits() macro Yury Norov
2021-04-01 8:35 ` Andy Shevchenko
2021-04-01 0:31 ` [PATCH 06/12] tools: sync small_const_nbits() macro with the kernel Yury Norov
2021-04-01 0:31 ` [PATCH 07/12] lib: inline _find_next_bit() wrappers Yury Norov
2021-04-01 8:37 ` Andy Shevchenko
2021-04-01 0:31 ` [PATCH 08/12] tools: sync find_next_bit implementation Yury Norov
2021-04-01 0:31 ` [PATCH 09/12] lib: add fast path for find_next_*_bit() Yury Norov
2021-04-01 8:48 ` Andy Shevchenko
2021-04-01 0:31 ` [PATCH 10/12] lib: add fast path for find_first_*_bit() and find_last_bit() Yury Norov
2021-04-01 8:58 ` Andy Shevchenko
2021-04-01 0:31 ` [PATCH 11/12] tools: sync lib/find_bit implementation Yury Norov
2021-05-10 15:27 ` Tetsuo Handa
2021-05-10 15:44 ` Andy Shevchenko
2021-05-10 17:21 ` Yury Norov [this message]
2021-05-10 22:51 ` Rikard Falkeborn
2021-05-11 7:28 ` Andy Shevchenko
2021-05-11 10:36 ` Rikard Falkeborn
2021-05-11 11:53 ` Tetsuo Handa
2021-05-11 20:37 ` Rikard Falkeborn
2021-05-12 7:48 ` Arnd Bergmann
2021-05-12 8:15 ` Rasmus Villemoes
2021-05-12 8:33 ` Arnd Bergmann
2021-05-11 12:17 ` Andy Shevchenko
2021-04-01 0:31 ` [PATCH 12/12] MAINTAINERS: Add entry for the bitmap API Yury Norov
2021-04-01 9:14 ` [PATCH v6 00/12] lib/find_bit: fast path for small bitmaps Andy Shevchenko
2021-04-01 9:28 ` Arnd Bergmann
2021-04-01 9:50 ` Andy Shevchenko
2021-04-02 0:32 ` Andrew Morton
-- strict thread matches above, loose matches on Subject: below --
2021-03-21 21:54 [PATCH v5 " Yury Norov
2021-03-21 21:54 ` [PATCH 11/12] tools: sync lib/find_bit implementation Yury Norov
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