From 4a9df2942470241d7a96f326f0e7012aacd36f2e Mon Sep 17 00:00:00 2001 From: "Yann E. MORIN" Date: Sun, 4 Jan 2015 15:17:14 +0100 Subject: [PATCH] package/erlang: fix detection of libatomic_ops For some platforms, hardware-assisted compare-and-swap may not be available, so libatomic_ops will not provide it. However, libatomic_ops can provide a purely software CAS 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/ [...] [Thomas: fix minor typos in commit log, add dependency on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS to the Erlang comment about thread and shared library dependency.] Signed-off-by: "Yann E. MORIN" Cc: Thomas Petazzoni Cc: Frank Hunleth Signed-off-by: Thomas Petazzoni --- ...g-build-fix.patch => 0001-build-fix.patch} | 0 ...truct-libatomic_ops-we-do-require-CA.patch | 70 +++++++++++++++++++ package/erlang/Config.in | 3 + package/erlang/erlang.mk | 7 +- 4 files changed, 77 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 diff --git a/package/erlang/erlang-build-fix.patch b/package/erlang/0001-build-fix.patch similarity index 100% rename from package/erlang/erlang-build-fix.patch rename to package/erlang/0001-build-fix.patch diff --git a/package/erlang/0002-erts-ethread-instruct-libatomic_ops-we-do-require-CA.patch b/package/erlang/0002-erts-ethread-instruct-libatomic_ops-we-do-require-CA.patch new file mode 100644 index 0000000000..8e401430fe --- /dev/null +++ b/package/erlang/0002-erts-ethread-instruct-libatomic_ops-we-do-require-CA.patch @@ -0,0 +1,70 @@ +From 439fa2eae78a8900bda120072335be19d626498c Mon Sep 17 00:00:00 2001 +From: "Yann E. MORIN" +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" +Cc: Thomas Petazzoni +Cc: Frank Hunleth +--- + 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 ++ #define AO_REQUIRE_CAS + #include "atomic_ops.h" + ]) + AC_DEFINE_UNQUOTED(ETHR_SIZEOF_AO_T, $ac_cv_sizeof_AO_t, [Define to the size of AO_t if libatomic_ops is used]) +-- +1.9.1 + diff --git a/package/erlang/Config.in b/package/erlang/Config.in index 56830dae44..51c72cb2b5 100644 --- a/package/erlang/Config.in +++ b/package/erlang/Config.in @@ -1,4 +1,5 @@ comment "erlang needs a toolchain w/ threads, shared library" + depends on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS depends on !BR2_TOOLCHAIN_HAS_THREADS && BR2_STATIC_LIBS config BR2_PACKAGE_ERLANG @@ -6,6 +7,8 @@ config BR2_PACKAGE_ERLANG depends on BR2_USE_MMU # fork() depends on BR2_TOOLCHAIN_HAS_THREADS depends on !BR2_STATIC_LIBS + depends on BR2_PACKAGE_LIBATOMIC_ARCH_SUPPORTS + select BR2_PACKAGE_LIBATOMIC_OPS help Erlang is a programming language used to build massively scalable soft real-time systems with requirements on high availability. diff --git a/package/erlang/erlang.mk b/package/erlang/erlang.mk index 0b8619e413..81ac436d95 100644 --- a/package/erlang/erlang.mk +++ b/package/erlang/erlang.mk @@ -13,6 +13,9 @@ ERLANG_LICENSE = EPL ERLANG_LICENSE_FILES = EPLICENCE ERLANG_INSTALL_STAGING = YES +# Touching erts/configure.in +ERLANG_AUTORECONF = YES + # The configure checks for these functions fail incorrectly ERLANG_CONF_ENV = ac_cv_func_isnan=yes ac_cv_func_isinf=yes @@ -22,10 +25,8 @@ ERLANG_CONF_ENV += erl_xcomp_sysroot=$(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. -- 2.30.2