1 files changed, 81 insertions, 0 deletions

diff --git a/meta/recipes-core/glibc/glibc/0006-Fix-atomic_fetch_xor_release.patch b/meta/recipes-core/glibc/glibc/0006-Fix-atomic_fetch_xor_release.patch
new file mode 100644
index 0000000000..7616efa183
--- /dev/null
+++ b/meta/recipes-core/glibc/glibc/0006-Fix-atomic_fetch_xor_release.patch
@@ -0,0 +1,81 @@
+From b671f20cc160238b62894d032a55baf85867106e Mon Sep 17 00:00:00 2001
+From: Catalin Enache <catalin.enache@windriver.com>
+Date: Fri, 30 Jun 2017 19:12:43 +0300
+Subject: [PATCH 6/6] Fix atomic_fetch_xor_release.
+
+No code uses atomic_fetch_xor_release except for the upcoming
+conditional variable rewrite. Therefore there is no user
+visible bug here. The use of atomic_compare_and_exchange_bool_rel
+is removed (since it doesn't exist anymore), and is replaced
+by atomic_compare_exchange_weak_release.
+
+We use weak_release because it provides better performance in
+the loop (the weak semantic) and because the xor is release MO
+(the release semantic). We don't reload expected in the loop
+because atomic_compare_and_exchange_weak_release does this for
+us as part of the CAS failure.
+
+It is otherwise a fairly plain conversion that fixes building
+the new condvar for 32-bit x86. Passes all regression tests
+for x86.
+
+Upstream-Status: Backport
+
+Author: Carlos O'Donell <carlos@systemhalted.org>
+Signed-off-by: Catalin Enache <catalin.enache@windriver.com>
+---
+ ChangeLog        |  6 ++++++
+ include/atomic.h | 19 +++++++++++--------
+ 2 files changed, 17 insertions(+), 8 deletions(-)
+
+diff --git a/ChangeLog b/ChangeLog
+index 44c518b..893262d 100644
+--- a/ChangeLog
++++ b/ChangeLog
+@@ -1,3 +1,9 @@
++2016-10-26  Carlos O'Donell  <carlos@redhat.com>
++
++       * include/atomic.h
++       [USE_COMPILER_ATOMIC_BUILTINS && !atomic_fetch_xor_release]
++       (atomic_fetch_xor_release): Use atomic_compare_exchange_weak_release.
++
+ 2017-04-04  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
+ 
+        * nptl/pthreadP.h (USE_REQUEUE_PI): Remove ununsed macro.
+diff --git a/include/atomic.h b/include/atomic.h
+index 5a8e7e7..c8b4664 100644
+--- a/include/atomic.h
++++ b/include/atomic.h
+@@ -777,18 +777,21 @@ void __atomic_link_error (void);
+ # endif
+ 
+ # ifndef atomic_fetch_xor_release
++/* Failing the atomic_compare_exchange_weak_release reloads the value in
++   __atg104_expected, so we need only do the XOR again and retry.  */
+ # define atomic_fetch_xor_release(mem, operand) \
+-  ({ __typeof (*(mem)) __atg104_old;                                         \
+-     __typeof (mem) __atg104_memp = (mem);                                   \
++  ({ __typeof (mem) __atg104_memp = (mem);                                   \
++     __typeof (*(mem)) __atg104_expected = (*__atg104_memp);                 \
++     __typeof (*(mem)) __atg104_desired;                                     \
+      __typeof (*(mem)) __atg104_op = (operand);                                      \
+                                                                              \
+      do                                                                              \
+-       __atg104_old = (*__atg104_memp);                                              \
+-     while (__builtin_expect                                                 \
+-           (atomic_compare_and_exchange_bool_rel (                           \
+-               __atg104_memp, __atg104_old ^ __atg104_op, __atg104_old), 0));\
+-                                                                             \
+-     __atg104_old; })
++       __atg104_desired = __atg104_expected ^ __atg104_op;                   \
++     while (__glibc_unlikely                                                 \
++           (atomic_compare_exchange_weak_release (                           \
++              __atg104_memp, &__atg104_expected, __atg104_desired)           \
++            == 0));                                                          \
++     __atg104_expected; })
+ #endif
+ 
+ #endif /* !USE_ATOMIC_COMPILER_BUILTINS  */
+-- 
+2.10.2
+