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