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* [Buildroot] [PATCH] erlang: selectively enable libatomic_ops
@ 2014-12-22  9:04 Frank Hunleth
  2014-12-22 17:13 ` Yann E. MORIN
  0 siblings, 1 reply; 5+ messages in thread
From: Frank Hunleth @ 2014-12-22  9:04 UTC (permalink / raw)
  To: buildroot

Erlang can use either the system libatomic_ops or its own version.
However, if using the system version, it must find implementations for
AO_compare_and_swap() and other calls.  Since these are not available on
all platforms, selectively enable the use of the system libatomic_ops.

Fixes:
http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/
http://autobuild.buildroot.net/results/c74/c743cfca629fb332bbb1327cf4ea360f0a4e4bfe/
http://autobuild.buildroot.net/results/095/095348d4d309c2a408a3b297b4325348ed1dd7e8/

Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
---
 package/erlang/Config.in | 10 ++++++++++
 package/erlang/erlang.mk |  4 +++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/package/erlang/Config.in b/package/erlang/Config.in
index 56830da..9caf1ec 100644
--- a/package/erlang/Config.in
+++ b/package/erlang/Config.in
@@ -26,6 +26,16 @@ config BR2_PACKAGE_ERLANG_SMP
 	  If you do not need SMP support, turning this option off reduces
 	  compile time and the size of the Erlang installation.
 
+config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
+	bool
+	select BR2_PACKAGE_LIBATOMIC_OPS
+	default y if BR2_ARM_CPU_ARMV7A || BR2_x86_64
+	help
+	  Use the system libatomic_ops on platforms that provide
+	  implementations for AO_store(), AO_load(), and AO_compare_and_swap().
+	  Platforms without support for those functions must still use the
+	  Erlang-provided implementation.
+
 config BR2_PACKAGE_ERLANG_MEGACO
 	bool "install megaco application"
 	help
diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
index 0b8619e..007053a 100644
--- a/package/erlang/erlang.mk
+++ b/package/erlang/erlang.mk
@@ -22,9 +22,11 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
 
 ERLANG_CONF_OPTS = --without-javac
 
-ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
+ifeq ($(BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS),y)
 ERLANG_DEPENDENCIES += libatomic_ops
 ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
+else
+ERLANG_CONF_OPTS += --without-libatomic_ops
 endif
 
 # erlang uses openssl for all things crypto. Since the host tools (such as
-- 
1.9.1

^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [Buildroot] [PATCH] erlang: selectively enable libatomic_ops
  2014-12-22  9:04 [Buildroot] [PATCH] erlang: selectively enable libatomic_ops Frank Hunleth
@ 2014-12-22 17:13 ` Yann E. MORIN
  2014-12-22 17:49   ` Frank Hunleth
  0 siblings, 1 reply; 5+ messages in thread
From: Yann E. MORIN @ 2014-12-22 17:13 UTC (permalink / raw)
  To: buildroot

Franck, All,

On 2014-12-22 04:04 -0500, Frank Hunleth spake thusly:
> Erlang can use either the system libatomic_ops or its own version.
> However, if using the system version, it must find implementations for
> AO_compare_and_swap() and other calls.  Since these are not available on
> all platforms, selectively enable the use of the system libatomic_ops.
> 
> Fixes:
> http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/
> http://autobuild.buildroot.net/results/c74/c743cfca629fb332bbb1327cf4ea360f0a4e4bfe/
> http://autobuild.buildroot.net/results/095/095348d4d309c2a408a3b297b4325348ed1dd7e8/
> 
> Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
> ---
>  package/erlang/Config.in | 10 ++++++++++
>  package/erlang/erlang.mk |  4 +++-
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/package/erlang/Config.in b/package/erlang/Config.in
> index 56830da..9caf1ec 100644
> --- a/package/erlang/Config.in
> +++ b/package/erlang/Config.in
> @@ -26,6 +26,16 @@ config BR2_PACKAGE_ERLANG_SMP
>  	  If you do not need SMP support, turning this option off reduces
>  	  compile time and the size of the Erlang installation.
>  
> +config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
> +	bool
> +	select BR2_PACKAGE_LIBATOMIC_OPS
> +	default y if BR2_ARM_CPU_ARMV7A || BR2_x86_64

Well, we already have BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS that defines
which architecture libatomic_ops supports.

So, unless AO_compare_and_swap() is not available on all those
architectures (and it seems it is), you should use that symbol instead.

> +	help
> +	  Use the system libatomic_ops on platforms that provide
> +	  implementations for AO_store(), AO_load(), and AO_compare_and_swap().
> +	  Platforms without support for those functions must still use the
> +	  Erlang-provided implementation.
> +
>  config BR2_PACKAGE_ERLANG_MEGACO
>  	bool "install megaco application"
>  	help
> diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
> index 0b8619e..007053a 100644
> --- a/package/erlang/erlang.mk
> +++ b/package/erlang/erlang.mk
> @@ -22,9 +22,11 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
>  
>  ERLANG_CONF_OPTS = --without-javac
>  
> -ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
> +ifeq ($(BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS),y)
>  ERLANG_DEPENDENCIES += libatomic_ops
>  ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
> +else
> +ERLANG_CONF_OPTS += --without-libatomic_ops
>  endif

So the consition for this block should stay the same, but the
--without-libatomic_ops addition is still welcome.

Regards,
Yann E. MORIN.

>  # erlang uses openssl for all things crypto. Since the host tools (such as
> -- 
> 1.9.1
> 
> _______________________________________________
> buildroot mailing list
> buildroot at busybox.net
> http://lists.busybox.net/mailman/listinfo/buildroot

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [Buildroot] [PATCH] erlang: selectively enable libatomic_ops
  2014-12-22 17:13 ` Yann E. MORIN
@ 2014-12-22 17:49   ` Frank Hunleth
  2014-12-22 21:24     ` Yann E. MORIN
  0 siblings, 1 reply; 5+ messages in thread
From: Frank Hunleth @ 2014-12-22 17:49 UTC (permalink / raw)
  To: buildroot

Hi Yann,

On Mon, Dec 22, 2014 at 12:13 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> Franck, All,
>
> On 2014-12-22 04:04 -0500, Frank Hunleth spake thusly:
>> Erlang can use either the system libatomic_ops or its own version.
>> However, if using the system version, it must find implementations for
>> AO_compare_and_swap() and other calls.  Since these are not available on
>> all platforms, selectively enable the use of the system libatomic_ops.
>>
>> Fixes:
>> http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/
>> http://autobuild.buildroot.net/results/c74/c743cfca629fb332bbb1327cf4ea360f0a4e4bfe/
>> http://autobuild.buildroot.net/results/095/095348d4d309c2a408a3b297b4325348ed1dd7e8/
>>
>> Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
>> ---
>>  package/erlang/Config.in | 10 ++++++++++
>>  package/erlang/erlang.mk |  4 +++-
>>  2 files changed, 13 insertions(+), 1 deletion(-)
>>
>> diff --git a/package/erlang/Config.in b/package/erlang/Config.in
>> index 56830da..9caf1ec 100644
>> --- a/package/erlang/Config.in
>> +++ b/package/erlang/Config.in
>> @@ -26,6 +26,16 @@ config BR2_PACKAGE_ERLANG_SMP
>>         If you do not need SMP support, turning this option off reduces
>>         compile time and the size of the Erlang installation.
>>
>> +config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
>> +     bool
>> +     select BR2_PACKAGE_LIBATOMIC_OPS
>> +     default y if BR2_ARM_CPU_ARMV7A || BR2_x86_64
>
> Well, we already have BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS that defines
> which architecture libatomic_ops supports.
>
> So, unless AO_compare_and_swap() is not available on all those
> architectures (and it seems it is), you should use that symbol instead.

That was my first thought, but if you look at the configs for the
failed builds, BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS=y is defined. E.g.:

   http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/config

Unfortunately, configure only prints the following to the build log so
it's not immediately obvious which function was missing:

   checking for a usable libatomic_ops implementation... no
   configure: error: No usable libatomic_ops implementation found

My assumption is that AO_compare_and_swap() is missing since that's
what I saw on a BR2_ARM_CPU_ARMV4 platform, but it could be something
else on BR2_ARM_CPU_ARMV5 (the config that I referenced above).

Thanks,
Frank

>
>> +     help
>> +       Use the system libatomic_ops on platforms that provide
>> +       implementations for AO_store(), AO_load(), and AO_compare_and_swap().
>> +       Platforms without support for those functions must still use the
>> +       Erlang-provided implementation.
>> +
>>  config BR2_PACKAGE_ERLANG_MEGACO
>>       bool "install megaco application"
>>       help
>> diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
>> index 0b8619e..007053a 100644
>> --- a/package/erlang/erlang.mk
>> +++ b/package/erlang/erlang.mk
>> @@ -22,9 +22,11 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
>>
>>  ERLANG_CONF_OPTS = --without-javac
>>
>> -ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
>> +ifeq ($(BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS),y)
>>  ERLANG_DEPENDENCIES += libatomic_ops
>>  ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
>> +else
>> +ERLANG_CONF_OPTS += --without-libatomic_ops
>>  endif
>
> So the consition for this block should stay the same, but the
> --without-libatomic_ops addition is still welcome.
>
> Regards,
> Yann E. MORIN.
>
>>  # erlang uses openssl for all things crypto. Since the host tools (such as
>> --
>> 1.9.1
>>
>> _______________________________________________
>> buildroot mailing list
>> buildroot at busybox.net
>> http://lists.busybox.net/mailman/listinfo/buildroot
>
> --
> .-----------------.--------------------.------------------.--------------------.
> |  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
> | +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
> | +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
> | http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
> '------------------------------^-------^------------------^--------------------'



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

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [Buildroot] [PATCH] erlang: selectively enable libatomic_ops
  2014-12-22 17:49   ` Frank Hunleth
@ 2014-12-22 21:24     ` Yann E. MORIN
  2014-12-23  0:57       ` Frank Hunleth
  0 siblings, 1 reply; 5+ messages in thread
From: Yann E. MORIN @ 2014-12-22 21:24 UTC (permalink / raw)
  To: buildroot

Frank, All,

On 2014-12-22 12:49 -0500, Frank Hunleth spake thusly:
> On Mon, Dec 22, 2014 at 12:13 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> > Franck, All,
> >
> > On 2014-12-22 04:04 -0500, Frank Hunleth spake thusly:
> >> Erlang can use either the system libatomic_ops or its own version.
> >> However, if using the system version, it must find implementations for
> >> AO_compare_and_swap() and other calls.  Since these are not available on
> >> all platforms, selectively enable the use of the system libatomic_ops.
> >>
> >> Fixes:
> >> http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/
> >> http://autobuild.buildroot.net/results/c74/c743cfca629fb332bbb1327cf4ea360f0a4e4bfe/
> >> http://autobuild.buildroot.net/results/095/095348d4d309c2a408a3b297b4325348ed1dd7e8/
> >>
> >> Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
> >> ---
> >>  package/erlang/Config.in | 10 ++++++++++
> >>  package/erlang/erlang.mk |  4 +++-
> >>  2 files changed, 13 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/package/erlang/Config.in b/package/erlang/Config.in
> >> index 56830da..9caf1ec 100644
> >> --- a/package/erlang/Config.in
> >> +++ b/package/erlang/Config.in
> >> @@ -26,6 +26,16 @@ config BR2_PACKAGE_ERLANG_SMP
> >>         If you do not need SMP support, turning this option off reduces
> >>         compile time and the size of the Erlang installation.
> >>
> >> +config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
> >> +     bool
> >> +     select BR2_PACKAGE_LIBATOMIC_OPS
> >> +     default y if BR2_ARM_CPU_ARMV7A || BR2_x86_64
> >
> > Well, we already have BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS that defines
> > which architecture libatomic_ops supports.
> >
> > So, unless AO_compare_and_swap() is not available on all those
> > architectures (and it seems it is), you should use that symbol instead.
> 
> That was my first thought, but if you look at the configs for the
> failed builds, BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS=y is defined. E.g.:
> 
>    http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/config
> 
> Unfortunately, configure only prints the following to the build log so
> it's not immediately obvious which function was missing:
> 
>    checking for a usable libatomic_ops implementation... no
>    configure: error: No usable libatomic_ops implementation found
> 
> My assumption is that AO_compare_and_swap() is missing since that's
> what I saw on a BR2_ARM_CPU_ARMV4 platform, but it could be something
> else on BR2_ARM_CPU_ARMV5 (the config that I referenced above).

Well, looking at output/build/erlang-17.4/erts/config.log, one can see:
    conftest.c:84:2: error: #error No compare_and_swap

which is consistent with the corresponding check, that looks for some
variant of AO_compare_and_swap.

So you were right, it's AO_compare_and_swap that is missing.

Let's see why...

Any definition of AO_compare_and_swap is enclosed in a pre-processor
block, conditional on AO_ARM_HAVE_LDREX.

AO_ARM_HAVE_LDREX is defined for anything armv6+ (except armv6m which is
thumb-only, but I doubt we have support for that, and that Linux even
runs on that processor).

So for ARM, we need armv6+ to use libatomic_ops.

However, I fail to see the reasoning for singling-out armv7a (and armv6)
and x86_64. Is there no other architecture that has AO_compare_and_swap()
or any of its variants? What about armv8 (AArch64), i386, sparc and the
others?

Maybe we could add this instead:

    config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
        bool
        default y
        depends on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS
        # On ARM, only armv6+ has the necessary AO_compare_and_swap()
        depends on BR2_ARM_CPU_ARMV6 || BR2_ARM_CPU_ARMV7A || !(BR2_arm || BR2_armeb)
        help
          Use the system libatomic_ops on platforms that provide
          implementations for AO_store(), AO_load(), and AO_compare_and_swap().
          Platforms without support for those functions must still use the
          Erlang-provided implementation.

> >>  config BR2_PACKAGE_ERLANG_MEGACO
> >>       bool "install megaco application"
> >>       help
> >> diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
> >> index 0b8619e..007053a 100644
> >> --- a/package/erlang/erlang.mk
> >> +++ b/package/erlang/erlang.mk
> >> @@ -22,9 +22,11 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
> >>
> >>  ERLANG_CONF_OPTS = --without-javac
> >>
> >> -ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
> >> +ifeq ($(BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS),y)
> >>  ERLANG_DEPENDENCIES += libatomic_ops
> >>  ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
> >> +else
> >> +ERLANG_CONF_OPTS += --without-libatomic_ops

It would also be good to add a comment that says something like:

    # --without-libatomic_ops means: do not use an external libatomic_ops;
    # atomic operations use an internal implementation instead.

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'

^ permalink raw reply	[flat|nested] 5+ messages in thread
* [Buildroot] [PATCH] erlang: selectively enable libatomic_ops
  2014-12-22 21:24     ` Yann E. MORIN
@ 2014-12-23  0:57       ` Frank Hunleth
  0 siblings, 0 replies; 5+ messages in thread
From: Frank Hunleth @ 2014-12-23  0:57 UTC (permalink / raw)
  To: buildroot

Yann,

On Mon, Dec 22, 2014 at 4:24 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> Frank, All,
>
> On 2014-12-22 12:49 -0500, Frank Hunleth spake thusly:
>> On Mon, Dec 22, 2014 at 12:13 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
>> > Franck, All,
>> >
>> > On 2014-12-22 04:04 -0500, Frank Hunleth spake thusly:
>> >> Erlang can use either the system libatomic_ops or its own version.
>> >> However, if using the system version, it must find implementations for
>> >> AO_compare_and_swap() and other calls.  Since these are not available on
>> >> all platforms, selectively enable the use of the system libatomic_ops.
>> >>
>> >> Fixes:
>> >> http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/
>> >> http://autobuild.buildroot.net/results/c74/c743cfca629fb332bbb1327cf4ea360f0a4e4bfe/
>> >> http://autobuild.buildroot.net/results/095/095348d4d309c2a408a3b297b4325348ed1dd7e8/
>> >>
>> >> Signed-off-by: Frank Hunleth <fhunleth@troodon-software.com>
>> >> ---
>> >>  package/erlang/Config.in | 10 ++++++++++
>> >>  package/erlang/erlang.mk |  4 +++-
>> >>  2 files changed, 13 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/package/erlang/Config.in b/package/erlang/Config.in
>> >> index 56830da..9caf1ec 100644
>> >> --- a/package/erlang/Config.in
>> >> +++ b/package/erlang/Config.in
>> >> @@ -26,6 +26,16 @@ config BR2_PACKAGE_ERLANG_SMP
>> >>         If you do not need SMP support, turning this option off reduces
>> >>         compile time and the size of the Erlang installation.
>> >>
>> >> +config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
>> >> +     bool
>> >> +     select BR2_PACKAGE_LIBATOMIC_OPS
>> >> +     default y if BR2_ARM_CPU_ARMV7A || BR2_x86_64
>> >
>> > Well, we already have BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS that defines
>> > which architecture libatomic_ops supports.
>> >
>> > So, unless AO_compare_and_swap() is not available on all those
>> > architectures (and it seems it is), you should use that symbol instead.
>>
>> That was my first thought, but if you look at the configs for the
>> failed builds, BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS=y is defined. E.g.:
>>
>>    http://autobuild.buildroot.net/results/eba/eba5bf85e9ff98916cd3638b5f13ab5bd54564d8/config
>>
>> Unfortunately, configure only prints the following to the build log so
>> it's not immediately obvious which function was missing:
>>
>>    checking for a usable libatomic_ops implementation... no
>>    configure: error: No usable libatomic_ops implementation found
>>
>> My assumption is that AO_compare_and_swap() is missing since that's
>> what I saw on a BR2_ARM_CPU_ARMV4 platform, but it could be something
>> else on BR2_ARM_CPU_ARMV5 (the config that I referenced above).
>
> Well, looking at output/build/erlang-17.4/erts/config.log, one can see:
>     conftest.c:84:2: error: #error No compare_and_swap
>
> which is consistent with the corresponding check, that looks for some
> variant of AO_compare_and_swap.
>
> So you were right, it's AO_compare_and_swap that is missing.
>
> Let's see why...
>
> Any definition of AO_compare_and_swap is enclosed in a pre-processor
> block, conditional on AO_ARM_HAVE_LDREX.
>
> AO_ARM_HAVE_LDREX is defined for anything armv6+ (except armv6m which is
> thumb-only, but I doubt we have support for that, and that Linux even
> runs on that processor).
>
> So for ARM, we need armv6+ to use libatomic_ops.
>
> However, I fail to see the reasoning for singling-out armv7a (and armv6)
> and x86_64. Is there no other architecture that has AO_compare_and_swap()
> or any of its variants? What about armv8 (AArch64), i386, sparc and the
> others?
>
> Maybe we could add this instead:
>
>     config BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS
>         bool
>         default y
>         depends on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS
>         # On ARM, only armv6+ has the necessary AO_compare_and_swap()
>         depends on BR2_ARM_CPU_ARMV6 || BR2_ARM_CPU_ARMV7A || !(BR2_arm || BR2_armeb)
>         help
>           Use the system libatomic_ops on platforms that provide
>           implementations for AO_store(), AO_load(), and AO_compare_and_swap().
>           Platforms without support for those functions must still use the
>           Erlang-provided implementation.
>

Completely agree. I've updated the patch. Thanks for investigating
more into which systems should have an AO_compare_and_swap()
implementation.

>> >>  config BR2_PACKAGE_ERLANG_MEGACO
>> >>       bool "install megaco application"
>> >>       help
>> >> diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk
>> >> index 0b8619e..007053a 100644
>> >> --- a/package/erlang/erlang.mk
>> >> +++ b/package/erlang/erlang.mk
>> >> @@ -22,9 +22,11 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
>> >>
>> >>  ERLANG_CONF_OPTS = --without-javac
>> >>
>> >> -ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
>> >> +ifeq ($(BR2_PACKAGE_ERLANG_USE_LIBATOMIC_OPS),y)
>> >>  ERLANG_DEPENDENCIES += libatomic_ops
>> >>  ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
>> >> +else
>> >> +ERLANG_CONF_OPTS += --without-libatomic_ops
>
> It would also be good to add a comment that says something like:
>
>     # --without-libatomic_ops means: do not use an external libatomic_ops;
>     # atomic operations use an internal implementation instead.

Done.

Thank you very much for spending time looking into the patch.

Frank

^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-12-23  0:57 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2014-12-22  9:04 [Buildroot] [PATCH] erlang: selectively enable libatomic_ops Frank Hunleth
2014-12-22 17:13 ` Yann E. MORIN
2014-12-22 17:49   ` Frank Hunleth
2014-12-22 21:24     ` Yann E. MORIN
2014-12-23  0:57       ` Frank Hunleth

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