| From 24484e80b3e329c9edee1995e102f8612eedb79c Mon Sep 17 00:00:00 2001 |
| From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> |
| Date: Tue, 13 May 2014 23:32:27 +0200 |
| Subject: [PATCH] Add AO_REQUIRE_CAS to fix build on ARM < v6 |
| |
| ARM earlier than ARMv6, such as ARMv4 and ARMv5 do not provide |
| optimize atomic operations in libatomic_ops. Since libunwind is using |
| such operations, it should define AO_REQUIRE_CAS before including |
| <atomic_ops.h> so that libatomic_ops knows it should use emulated |
| atomic operations instead (even though they are obviously a lot more |
| expensive). |
| |
| Also, while real atomic operations are all inline functions and |
| therefore linking against libatomic_ops was not required, the emulated |
| atomic operations actually require linking against libatomic_ops, so |
| the commented AC_CHECK_LIB test in acinclude.m4 is uncommented to make |
| sure we link against libatomic_ops. |
| |
| Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> |
| --- |
| acinclude.m4 | 8 +------- |
| include/libunwind_i.h | 1 + |
| 2 files changed, 2 insertions(+), 7 deletions(-) |
| |
| diff --git a/acinclude.m4 b/acinclude.m4 |
| index 497f7c2..9c15af1 100644 |
| --- a/acinclude.m4 |
| +++ b/acinclude.m4 |
| @@ -22,11 +22,5 @@ fi]) |
| AC_DEFUN([CHECK_ATOMIC_OPS], |
| [dnl Check whether the system has the atomic_ops package installed. |
| AC_CHECK_HEADERS(atomic_ops.h) |
| -# |
| -# Don't link against libatomic_ops for now. We don't want libunwind |
| -# to depend on libatomic_ops.so. Fortunately, none of the platforms |
| -# we care about so far need libatomic_ops.a (everything is done via |
| -# inline macros). |
| -# |
| -# AC_CHECK_LIB(atomic_ops, main) |
| + AC_CHECK_LIB(atomic_ops, main) |
| ]) |
| diff --git a/include/libunwind_i.h b/include/libunwind_i.h |
| index 23f615e..deabdfd 100644 |
| --- a/include/libunwind_i.h |
| +++ b/include/libunwind_i.h |
| @@ -95,6 +95,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ |
| (pthread_mutex_unlock != NULL ? pthread_mutex_unlock (l) : 0) |
| |
| #ifdef HAVE_ATOMIC_OPS_H |
| +# define AO_REQUIRE_CAS |
| # include <atomic_ops.h> |
| static inline int |
| cmpxchg_ptr (void *addr, void *old, void *new) |
| -- |
| 1.9.2 |
| |
