From 73fe55d7522864d20026dc8d427026dc4078f9cc Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Wed, 6 Feb 2019 20:46:00 +0000 Subject: [PATCH] re PR go/89199 (libgo regression in implementation of CompareAndSwap functions resulting in intermittent testcase failures on ppc64le power9 after r268458) 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 --- gcc/go/gofrontend/MERGE | 2 +- libgo/go/sync/atomic/atomic.c | 10 +++++----- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE index 100d30e2c73..63499b36d19 100644 --- 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 25e439dac2b..90a4ff3f922 100644 --- 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); } -- 2.30.2