re PR go/89199 (libgo regression in implementation of CompareAndSwap functions result...

	PR go/89199
    sync/atomic: use strong form of atomic_compare_exchange_n

    In the recent change to use atomic_compare_exchange_n I thought we
    could use the weak form, which can spuriously fail. But that is not
    how it is implemented in the gc library, and it is not what the rest
    of the library expects.

    Thanks to Lynn Boger for identifying the problem.

    Fixes https://gcc.gnu.org/PR89199

    Reviewed-on: https://go-review.googlesource.com/c/161359

From-SVN: r268591

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 100d30e2c738cd678fe01da71ffa3da64f57e29c..63499b36d195029ca532dfbefb7b616515afd005 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-74ffeddbe6fef446129af65581b3a9094715bc22
+d89db31db68d09aa13a6137122cc096c1d92597b
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

diff --git a/libgo/go/sync/atomic/atomic.c b/libgo/go/sync/atomic/atomic.c
index 25e439dac2b313353d9dbba0ae36762cc0fce658..90a4ff3f9224639a70ea3d4f5bba4f3dd14df50c 100644 (file)
--- a/libgo/go/sync/atomic/atomic.c
+++ b/libgo/go/sync/atomic/atomic.c
@@ -69,7 +69,7 @@ _Bool CompareAndSwapInt32 (int32_t *, int32_t, int32_t)
 _Bool
 CompareAndSwapInt32 (int32_t *val, int32_t old, int32_t new)
 {
-  return __atomic_compare_exchange_n (val, &old, new, true, __ATOMIC_SEQ_CST,
+  return __atomic_compare_exchange_n (val, &old, new, false, __ATOMIC_SEQ_CST,
                                      __ATOMIC_RELAXED);
 }
 
@@ -82,7 +82,7 @@ CompareAndSwapInt64 (int64_t *val, int64_t old, int64_t new)
 {
   if (((uintptr_t) val & 7) != 0)
     val = NULL;
-  return __atomic_compare_exchange_n (val, &old, new, true, __ATOMIC_SEQ_CST,
+  return __atomic_compare_exchange_n (val, &old, new, false, __ATOMIC_SEQ_CST,
                                      __ATOMIC_RELAXED);
 }
 
@@ -93,7 +93,7 @@ _Bool CompareAndSwapUint32 (uint32_t *, uint32_t, uint32_t)
 _Bool
 CompareAndSwapUint32 (uint32_t *val, uint32_t old, uint32_t new)
 {
-  return __atomic_compare_exchange_n (val, &old, new, true, __ATOMIC_SEQ_CST,
+  return __atomic_compare_exchange_n (val, &old, new, false, __ATOMIC_SEQ_CST,
                                      __ATOMIC_RELAXED);
 }
 
@@ -106,7 +106,7 @@ CompareAndSwapUint64 (uint64_t *val, uint64_t old, uint64_t new)
 {
   if (((uintptr_t) val & 7) != 0)
     val = NULL;
-  return __atomic_compare_exchange_n (val, &old, new, true, __ATOMIC_SEQ_CST,
+  return __atomic_compare_exchange_n (val, &old, new, false, __ATOMIC_SEQ_CST,
                                      __ATOMIC_RELAXED);
 }
 
@@ -117,7 +117,7 @@ _Bool CompareAndSwapUintptr (uintptr_t *, uintptr_t, uintptr_t)
 _Bool
 CompareAndSwapUintptr (uintptr_t *val, uintptr_t old, uintptr_t new)
 {
-  return __atomic_compare_exchange_n (val, &old, new, true, __ATOMIC_SEQ_CST,
+  return __atomic_compare_exchange_n (val, &old, new, false, __ATOMIC_SEQ_CST,
                                      __ATOMIC_RELAXED);
 }