similarity index 100%
rename from package/erlang/erlang-build-fix.patch
rename to package/erlang/0001-build-fix.patch
new file mode 100644
@@ -0,0 +1,70 @@
+From 439fa2eae78a8900bda120072335be19d626498c Mon Sep 17 00:00:00 2001
+From: "Yann E. MORIN" <yann.morin.1998@free.fr>
+Date: Sun, 28 Dec 2014 23:39:40 +0100
+Subject: [PATCH] erts/ethread: instruct libatomic_ops we do require CAS
+
+We do require compare-and-swap (CAS), so we must instruct libatomic_ops
+to provide it, even if the architecture does not have instructions for
+it.
+
+For example, on ARM, LDREX is required for fast CAS. But LDREX is only
+available on ARMv6, so by default libatomic_ops will not have CAS for
+anything below, like ARMv5. But ARMv5 is always UP, so using an
+emulated CAS (that is signal-asyn-safe) is still possible (albeit much
+slower).
+
+Tell libatomic_ops to provide CAS, even if the hardware is not capable
+of it, by using emulated CAS, as per libatomic_ops dosc:
+ https://github.com/ivmai/libatomic_ops/blob/master/doc/README.txt#L28
+
+ If this is included after defining AO_REQUIRE_CAS, then the package
+ will make an attempt to emulate compare-and-swap in a way that (at
+ least on Linux) should still be async-signal-safe.
+
+Thanks go to Thomas for all this insight! :-)
+Thanks go to Frank for reporting the issue! :-)
+
+Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
+Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
+Cc: Frank Hunleth <fhunleth@troodon-software.com>
+---
+ erts/include/internal/libatomic_ops/ethread.h | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/erts/include/internal/libatomic_ops/ethread.h b/erts/include/internal/libatomic_ops/ethread.h
+index d65ee19..71d3598 100644
+--- a/erts/include/internal/libatomic_ops/ethread.h
++++ b/erts/include/internal/libatomic_ops/ethread.h
+@@ -35,6 +35,7 @@
+
+ #define ETHR_NATIVE_IMPL__ "libatomic_ops"
+
++#define AO_REQUIRE_CAS
+ #include "atomic_ops.h"
+ #include "ethr_membar.h"
+ #include "ethr_atomic.h"
+diff --git a/erts/aclocal.m4 b/erts/aclocal.m4
+index d65ee19..71d3598 100644
+--- a/erts/aclocal.m4
++++ b/erts/aclocal.m4
+@@ -1414,7 +1414,8 @@
+ fi;;
+ esac
+ ethr_have_libatomic_ops=no
+- AC_TRY_LINK([#include "atomic_ops.h"],
++ AC_TRY_LINK([#define AO_REQUIRE_CAS
++ #include "atomic_ops.h"],
+ [
+ volatile AO_t x;
+ AO_t y;
+@@ -1455,6 +1455,7 @@
+ AC_CHECK_SIZEOF(AO_t, ,
+ [
+ #include <stdio.h>
++ #define AO_REQUIRE_CAS
+ #include "atomic_ops.h"
+ ])
+ AC_DEFINE_UNQUOTED(ETHR_SIZEOF_AO_T, $ac_cv_sizeof_AO_t, [Define to the size of AO_t if libatomic_ops is used])
+--
+1.9.1
+
@@ -6,6 +6,8 @@ config BR2_PACKAGE_ERLANG
depends on BR2_USE_MMU # fork()
depends on BR2_TOOLCHAIN_HAS_THREADS
depends on !BR2_STATIC_LIBS
+ depends on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS
+ select BR2_PACKAGE_LIBATOMIC_OPS
help
Erlang is a programming language used to build massively scalable
soft real-time systems with requirements on high availability.
@@ -13,6 +13,9 @@ ERLANG_LICENSE = EPL
ERLANG_LICENSE_FILES = EPLICENCE
ERLANG_INSTALL_STAGING = YES
+# Touching erts/configure.in
+ERLANG_AUTORECONF = YES
+
# The configure checks for these functions fail incorrectly
ERLANG_CONF_ENV = ac_cv_func_isnan=yes ac_cv_func_isinf=yes
@@ -22,10 +25,8 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(STAGING_DIR)
ERLANG_CONF_OPTS = --without-javac
-ifeq ($(BR2_PACKAGE_LIBATOMIC_OPS),y)
ERLANG_DEPENDENCIES += libatomic_ops
-ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr
-endif
+ERLANG_CONF_OPTS += --with-libatomic_ops=$(STAGING_DIR)/usr LIBS=-latomic_ops
# 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.
For some platforms, hardware-assisted compare-and-swap may not be available, so libatomic will not provide it. However, libatomic_ops can provide a puerly software CASE emulation, but must be instructed to do so. erlang just forgot to tell libatomic_ops that it does require CAS. Fix that by defining AO_REQUIRE_CAS before including atmoic_ops.h, like is done in libunwind, as pointed out by Thomas. Also, erlang has a convoluted, mind-alterating set on aclocal.m4 macros, that just forgets to link against -latomic_ops when checking CAS is available, so that even if CAS is available, configure chokes. Since I would like to keep the little sanity I still have, just force linking with -latomic_ops. This is useless when the check is natrally sucessful (i.e. on platforms where CAS is available in HW), but we would eventually link with -latomic_ops there, too; it's just redundant. Overall, just consider that erlang requires libatomic_ops, so forcibly depend on it, it is easier than trying to disable it. We can revisit that whenever someone wants to run erlang on a platform for which there is no libatomic_ops support. Fixes a slew of autobuild ARM failures: http://autobuild.buildroot.org/results/e7b/e7bfc4893dea6b133f0794ef44d50ad89bcb6662/ http://autobuild.buildroot.org/results/3e9/3e9c307f1ec6536482641019dcaa94677f7267a3/ http://autobuild.buildroot.org/results/a85/a85ca414e5b67af46510abd7b610eb5ae8661de4/ [...] Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Cc: Frank Hunleth <fhunleth@troodon-software.com> --- ...erlang-build-fix.patch => 0001-build-fix.patch} | 0 ...d-instruct-libatomic_ops-we-do-require-CA.patch | 70 ++++++++++++++++++++++ package/erlang/Config.in | 2 + package/erlang/erlang.mk | 7 ++- 4 files changed, 76 insertions(+), 3 deletions(-) rename package/erlang/{erlang-build-fix.patch => 0001-build-fix.patch} (100%) create mode 100644 package/erlang/0002-erts-ethread-instruct-libatomic_ops-we-do-require-CA.patch