Acked-by: Ethan Jackson <et...@nicira.com>
On Thu, Jul 18, 2013 at 2:26 PM, Ben Pfaff <b...@nicira.com> wrote:
> We found out earlier that GCC sometimes produces an error only at link time
> for atomic built-ins that are not supported on a platform. This actually
> tries the link at configure time and should thus reliably detect whether
> the atomic built-ins are really supported.
>
> Signed-off-by: Ben Pfaff <b...@nicira.com>
> ---
> I thought I'd already sent out these patches, but it looks like they
> never made it to ovs-dev or patchwork.
>
> configure.ac | 1 +
> lib/ovs-atomic.h | 2 +-
> m4/openvswitch.m4 | 72
> +++++++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 74 insertions(+), 1 deletions(-)
>
> diff --git a/configure.ac b/configure.ac
> index e4f9991..e44ae36 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -82,6 +82,7 @@ OVS_CHECK_GROFF
> OVS_CHECK_GNU_MAKE
> OVS_CHECK_CACHE_TIME
> OVS_CHECK_TLS
> +OVS_CHECK_GCC4_ATOMICS
> OVS_CHECK_ATOMIC_ALWAYS_LOCK_FREE(1)
> OVS_CHECK_ATOMIC_ALWAYS_LOCK_FREE(2)
> OVS_CHECK_ATOMIC_ALWAYS_LOCK_FREE(4)
> diff --git a/lib/ovs-atomic.h b/lib/ovs-atomic.h
> index a0a34f3..3fc9dcb 100644
> --- a/lib/ovs-atomic.h
> +++ b/lib/ovs-atomic.h
> @@ -240,7 +240,7 @@
> #include "ovs-atomic-c11.h"
> #elif __GNUC__ >= 4 && __GNUC_MINOR__ >= 7
> #include "ovs-atomic-gcc4.7+.h"
> - #elif __GNUC__ >= 4
> + #elif HAVE_GCC4_ATOMICS
> #include "ovs-atomic-gcc4+.h"
> #else
> #include "ovs-atomic-pthreads.h"
> diff --git a/m4/openvswitch.m4 b/m4/openvswitch.m4
> index ca80506..e6e5d08 100644
> --- a/m4/openvswitch.m4
> +++ b/m4/openvswitch.m4
> @@ -426,6 +426,78 @@ static thread_local int var;], [return var;])],
> fi
> fi])
>
> +dnl OVS_CHECK_GCC4_ATOMICS
> +dnl
> +dnl Checks whether the compiler and linker support GCC 4.0+ atomic built-ins.
> +dnl A compile-time only check is not enough because the compiler defers
> +dnl unimplemented built-ins to libgcc, which sometimes also lacks
> +dnl implementations.
> +AC_DEFUN([OVS_CHECK_GCC4_ATOMICS],
> + [AC_CACHE_CHECK(
> + [whether $CC supports GCC 4.0+ atomic built-ins],
> + [ovs_cv_gcc4_atomics],
> + [AC_LINK_IFELSE(
> + [AC_LANG_PROGRAM([[#include <stdlib.h>
> +
> +#define ovs_assert(expr) if (!(expr)) abort();
> +#define TEST_ATOMIC_TYPE(TYPE) \
> + { \
> + TYPE x = 1; \
> + TYPE orig; \
> + \
> + __sync_synchronize(); \
> + ovs_assert(x == 1); \
> + \
> + __sync_synchronize(); \
> + x = 3; \
> + __sync_synchronize(); \
> + ovs_assert(x == 3); \
> + \
> + orig = __sync_fetch_and_add(&x, 1); \
> + ovs_assert(orig == 3); \
> + __sync_synchronize(); \
> + ovs_assert(x == 4); \
> + \
> + orig = __sync_fetch_and_sub(&x, 2); \
> + ovs_assert(orig == 4); \
> + __sync_synchronize(); \
> + ovs_assert(x == 2); \
> + \
> + orig = __sync_fetch_and_or(&x, 6); \
> + ovs_assert(orig == 2); \
> + __sync_synchronize(); \
> + ovs_assert(x == 6); \
> + \
> + orig = __sync_fetch_and_and(&x, 10); \
> + ovs_assert(orig == 6); \
> + __sync_synchronize(); \
> + ovs_assert(x == 2); \
> + \
> + orig = __sync_fetch_and_xor(&x, 10); \
> + ovs_assert(orig == 2); \
> + __sync_synchronize(); \
> + ovs_assert(x == 8); \
> + }]], [dnl
> +TEST_ATOMIC_TYPE(char);
> +TEST_ATOMIC_TYPE(unsigned char);
> +TEST_ATOMIC_TYPE(signed char);
> +TEST_ATOMIC_TYPE(short);
> +TEST_ATOMIC_TYPE(unsigned short);
> +TEST_ATOMIC_TYPE(int);
> +TEST_ATOMIC_TYPE(unsigned int);
> +TEST_ATOMIC_TYPE(long int);
> +TEST_ATOMIC_TYPE(unsigned long int);
> +TEST_ATOMIC_TYPE(long long int);
> +TEST_ATOMIC_TYPE(unsigned long long int);
> +])],
> + [ovs_cv_gcc4_atomics=yes],
> + [ovs_cv_gcc4_atomics=no])])
> + if test $ovs_cv_gcc4_atomics = yes; then
> + AC_DEFINE([HAVE_GCC4_ATOMICS], [1],
> + [Define to 1 if the C compiler and linker supports the GCC
> 4.0+
> + atomic built-ins.])
> + fi])
> +
> dnl OVS_CHECK_ATOMIC_ALWAYS_LOCK_FREE(SIZE)
> dnl
> dnl Checks __atomic_always_lock_free(SIZE, 0)
> --
> 1.7.2.5
>
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev
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