[Buildroot] [PATCH 1/1] package/numactl: needs atomic

[Buildroot] [PATCH 1/1] package/numactl: needs atomic

[Fabrice Fontaine]

numactl unconditionally uses __atomic_fetch_and resulting in the
following build failure on microblaze since commit
4ed540ddf59bec4b389be44d7f42820d2466904f:

/nvmedata/autobuild/instance-5/output-1/host/lib/gcc/microblaze-buildroot-linux-uclibc/10.3.0/../../../../microblaze-buildroot-linux-uclibc/bin/ld: ./.libs/libnuma.a(libnuma.o): in function `numa_node_to_cpus_v1':
(.text+0x2a34): undefined reference to `__atomic_fetch_and_1'

Fixes:
 - http://autobuild.buildroot.org/results/e225cb83dae390d9dc543d4da85c52180efbd40a

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
---
 package/numactl/Config.in  | 1 +
 package/rt-tests/Config.in | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/package/numactl/Config.in b/package/numactl/Config.in
index 23cf7facb0..325a05d609 100644
--- a/package/numactl/Config.in
+++ b/package/numactl/Config.in
@@ -1,6 +1,7 @@
 config BR2_PACKAGE_NUMACTL
 	bool "numactl"
 	depends on BR2_USE_MMU # madvise()
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	help
 	  numactl allows you to run your application on specific cpus
 	  and memory nodes. It does this by supplying a NUMA memory
diff --git a/package/rt-tests/Config.in b/package/rt-tests/Config.in
index 8efa3d194e..ccfa040d70 100644
--- a/package/rt-tests/Config.in
+++ b/package/rt-tests/Config.in
@@ -1,6 +1,7 @@
 config BR2_PACKAGE_RT_TESTS
 	bool "rt-tests"
 	depends on BR2_TOOLCHAIN_HAS_SYNC_4 # __sync_*_4 intrisics
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC # numactl
 	depends on BR2_TOOLCHAIN_HAS_THREADS_NPTL
 	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_5
 	depends on BR2_USE_MMU # fork(), numactl
@@ -32,6 +33,7 @@ comment "rt-tests may not work on MIPS with an external uClibc toolchain"
 
 comment "rt-tests needs a uClibc or glibc toolchain w/ NPTL, headers >= 4.5, dynamic library"
 	depends on BR2_TOOLCHAIN_HAS_SYNC_4
+	depends on BR2_TOOLCHAIN_HAS_ATOMIC
 	depends on !BR2_TOOLCHAIN_HAS_THREADS_NPTL || BR2_STATIC_LIBS \
 		|| BR2_TOOLCHAIN_USES_MUSL || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_4_5
 	depends on BR2_USE_MMU
-- 
2.35.1

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Re: [Buildroot] [PATCH 1/1] package/numactl: needs atomic

[Thomas Petazzoni via buildroot]

On Wed, 27 Apr 2022 22:50:57 +0200
Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:

> numactl unconditionally uses __atomic_fetch_and resulting in the
> following build failure on microblaze since commit
> 4ed540ddf59bec4b389be44d7f42820d2466904f:

This explanation is unfortunately incorrect. It has nothing to do with
microblaze, because BR2_TOOLCHAIN_HAS_ATOMIC is true on microblaze:

config BR2_TOOLCHAIN_HAS_LIBATOMIC
        bool
        default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 && \
                !BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_AARCH64 && \
                BR2_TOOLCHAIN_HAS_THREADS && \
                !BR2_BINFMT_FLAT

config BR2_TOOLCHAIN_HAS_ATOMIC
        bool
        default y if BR2_TOOLCHAIN_HAS_LIBATOMIC
        default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_arm
        default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_armeb
        default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_xtensa
        default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_ARCH_IS_64

However, the key thing is that the build failure
http://autobuild.buildroot.org/results/e225cb83dae390d9dc543d4da85c52180efbd40a
has thread support disabled, and when threads are disabled, libatomic
is not built, and therefore BR2_TOOLCHAIN_HAS_LIBATOMIC is false.

However, I don't see anywhere in the numactl build system where
-latomic is passed. Does it build on architectures that need to link
against libatomic to get atomic intrinsics?

Could you double check this, and rework the commit message?

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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Re: [Buildroot] [PATCH 1/1] package/numactl: needs atomic

[Fabrice Fontaine]

Le jeu. 28 avr. 2022 à 23:45, Thomas Petazzoni
<thomas.petazzoni@bootlin.com> a écrit :
>
> On Wed, 27 Apr 2022 22:50:57 +0200
> Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:
>
> > numactl unconditionally uses __atomic_fetch_and resulting in the
> > following build failure on microblaze since commit
> > 4ed540ddf59bec4b389be44d7f42820d2466904f:
>
> This explanation is unfortunately incorrect. It has nothing to do with
> microblaze, because BR2_TOOLCHAIN_HAS_ATOMIC is true on microblaze:
>
> config BR2_TOOLCHAIN_HAS_LIBATOMIC
>         bool
>         default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_8 && \
>                 !BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_AARCH64 && \
>                 BR2_TOOLCHAIN_HAS_THREADS && \
>                 !BR2_BINFMT_FLAT
>
> config BR2_TOOLCHAIN_HAS_ATOMIC
>         bool
>         default y if BR2_TOOLCHAIN_HAS_LIBATOMIC
>         default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_arm
>         default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_armeb
>         default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_xtensa
>         default y if BR2_TOOLCHAIN_GCC_AT_LEAST_4_7 && BR2_ARCH_IS_64
>
> However, the key thing is that the build failure
> http://autobuild.buildroot.org/results/e225cb83dae390d9dc543d4da85c52180efbd40a
> has thread support disabled, and when threads are disabled, libatomic
> is not built, and therefore BR2_TOOLCHAIN_HAS_LIBATOMIC is false.
>
> However, I don't see anywhere in the numactl build system where
> -latomic is passed. Does it build on architectures that need to link
> against libatomic to get atomic intrinsics?

Linking with -latomic is done thanks to 0002-link-with-latomic-if-needed.patch.
This patch was added to fix the build on architectures such as sparcv8.
However, I don't understand why the build fails on microblaze without libatomic.
Are we sure that microblaze really supports atomic without libatomic?

>
> Could you double check this, and rework the commit message?
>
> Thanks!
>
> Thomas
> --
> Thomas Petazzoni, co-owner and CEO, Bootlin
> Embedded Linux and Kernel engineering and training
> https://bootlin.com

Best Regards,

Fabrice
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Re: [Buildroot] [PATCH 1/1] package/numactl: needs atomic

[Thomas Petazzoni via buildroot]

Hello Fabrice,

On Fri, 29 Apr 2022 09:05:21 +0200
Fabrice Fontaine <fontaine.fabrice@gmail.com> wrote:

> > However, the key thing is that the build failure
> > http://autobuild.buildroot.org/results/e225cb83dae390d9dc543d4da85c52180efbd40a
> > has thread support disabled, and when threads are disabled, libatomic
> > is not built, and therefore BR2_TOOLCHAIN_HAS_LIBATOMIC is false.
> >
> > However, I don't see anywhere in the numactl build system where
> > -latomic is passed. Does it build on architectures that need to link
> > against libatomic to get atomic intrinsics?  
> 
> Linking with -latomic is done thanks to 0002-link-with-latomic-if-needed.patch.
> This patch was added to fix the build on architectures such as sparcv8.

Ah, I missed that patch, thanks for pointing it out!

> However, I don't understand why the build fails on microblaze without libatomic.
> Are we sure that microblaze really supports atomic without libatomic?

I explained it in my previous e-mail I think :-)

It fails because the configuration you're pointing to has threads
disabled, and when threads are disabled, libatomic is not
built/provided by gcc. This is properly handled by
BR2_TOOLCHAIN_HAS_LIBATOMIC being false in such configurations.

So basically, your patch is correct (IMO), but the commit log isn't:
the problem isn't Microblaze specific, but would happen on any
architecture that needs libatomic to provide atomic intrinsics.

Thanks!

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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