[Buildroot] [PATCH v3 1/2] erlang: use erlang's native atomic ops

Frank Hunleth fhunleth at troodon-software.com
Wed Mar 2 20:47:02 UTC 2016


Hi Arnout, all,

On Sat, Feb 27, 2016 at 5:17 PM, Arnout Vandecappelle <arnout at mind.be> wrote:
> On 02/21/16 20:17, Frank Hunleth wrote:
>> Now that we're using Erlang 18, the preferred atomic ops implementation
>> for Erlang is its own built-in implementation, so use it.  It is still
>> possible to use libatomic_ops if the native implementation does not
>> work. BR2_PACKAGE_ERLANG_ARCH_SUPPORTS is added now that
>> BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS is no longer appropriate for
>> checking whether Erlang can be built for a platform.
>>
>> This fixes an autobuilder failure when using libatomic_ops on aarch64.
>> Erlang's native atomic ops implementation works on this platform.
>>
>> Fixes:
>> http://autobuild.buildroot.net/results/0cd/0cd22eb74fa29e5a85bf897762e16ab3daf33962/
>>
>> Signed-off-by: Frank Hunleth <fhunleth at troodon-software.com>
>> ---
> [snip]
>> +config BR2_PACKAGE_ERLANG_ARCH_SUPPORTS
>> +     bool
>> +     default y if BR2_i386 || BR2_x86_64 || BR2_powerpc || BR2_sparc_v9 || BR2_arm || BR2_aarch64 # case (1)
>
>  This line is too long, please split it.
>
>> +     default y if BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS # case (4)
>>
>>  config BR2_PACKAGE_ERLANG
>>       bool "erlang"
>>       depends on BR2_USE_MMU # fork()
>>       depends on !BR2_STATIC_LIBS
>> -     depends on BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS
>> -     select BR2_PACKAGE_LIBATOMIC_OPS
>> +     depends on BR2_PACKAGE_ERLANG_ARCH_SUPPORTS
>>       help
>>         Erlang is a programming language used to build massively scalable
>>         soft real-time systems with requirements on high availability.
>> @@ -20,6 +36,14 @@ config BR2_PACKAGE_ERLANG
>>
>>  if BR2_PACKAGE_ERLANG
>>
>> +config BR2_PACKAGE_ERLANG_LIBATOMIC_OPS
>> +     bool "libatomic_ops"
>
>  Does it make sense to let the user select this? I don't think so...
>
>  I think we should have:
>
> config BR2_PACKAGE_ERLANG_ARCH_SUPPORTS_DIRECTLY # case (1)
>         bool
>         default y if BR2_i386 || BR2_x86_64 || BR2_powerpc || \
>                 BR2_sparc_v9 || BR2_arm # aarch64 causes build failures
>
> config BR2_PACKAGE_ERLANG_ARCH_SUPPORTS
>         bool
>         default y if BR2_PACKAGE_ERLANG_ARCH_SUPPORTS_DIRECTLY
>         default y if BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS # case (4)
>
> and nothing more.

The more I think about this patch, the more I want to drop all
references to libatomic_ops. The reason is that the native Erlang
atomic ops implementation supports almost every platform supported by
libatomic_ops. In fact, it looks like every _defconfig in Buildroot
that supports Erlang uses the native atomic ops implementation rather
than libatomic_ops. (I actually tried building all _defconfigs at one
point, but I'll double check if there are doubts.)

Does it make sense to remove libatomic_ops altogether? I think the
original reason for including it doesn't apply now that we upgraded to
Erlang 18.

Thanks,
Frank


>
>> +     depends on BR2_PACKAGE_LIBATOMIC_OPS_ARCH_SUPPORTS
>> +     depends on !BR2_aarch64 # causes build failures
>> +     select BR2_PACKAGE_LIBATOMIC_OPS
>> +     help
>> +       Use libatomic_ops instead of Erlang's native atomic ops support.
>> +
>>  config BR2_PACKAGE_ERLANG_SMP
>>       bool "enable SMP support"
>>       help
>> @@ -38,3 +62,8 @@ config BR2_PACKAGE_ERLANG_MEGACO
>>         enable it.
>>
>>  endif # BR2_PACKAGE_ERLANG
>> +
>> +comment "erlang needs a toolchain w/ dynamic library, atomic_ops"
>> +     depends on BR2_USE_MMU # fork()
>> +     depends on BR2_STATIC_LIBS || !BR2_PACKAGE_ERLANG_ARCH_SUPPORTS
>
>  This should depend on BR2_PACKAGE_ERLANG_ARCH_SUPPORTS, so:
>
> comment "erlang needs a toolchain w/ dynamic library"
>         depends on BR2_PACKAGE_ERLANG_ARCH_SUPPORTS
>         depends on BR2_USE_MMU # fork()
>         depends on BR2_STATIC_LIBS
>
> and that should ideally be a separate patch, or at least mentioned in the commit
> message.
>
>> +
>> diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
>> index 638d2c2..8257ab4 100644
>> --- a/package/erlang/erlang.mk
>> +++ b/package/erlang/erlang.mk
>> @@ -30,8 +30,12 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
>>
>>  ERLANG_CONF_OPTS = --without-javac
>>
>> +# Erlang uses its own native atomic ops implementation if support is
>> +# available. Override this if the user wants libatomic_ops.
>> +ifeq ($(BR2_PACKAGE_ERLANG_LIBATOMIC_OPS),y)
>
>  So here it should be
>
> ifeq ($(BR2_PACKAGE_ERLANG_ARCH_SUPPORTS_DIRECTLY),)
>
>
>  Regards,
>  Arnout
>
>>  ERLANG_DEPENDENCIES += libatomic_ops
>>  ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr LIBS=-latomic_ops
>> +endif
>>
>>  # erlang uses openssl for all things crypto. Since the host tools (such as
>>  # rebar) uses crypto, we need to build host-erlang with support for openssl.
>>
>
>
> --
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF



-- 
Frank Hunleth
Troodon Software LLC
Embedded Software Development
http://troodon-software.com/


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