From: Ivan Maidanski <ivmai@mail.ru>
Date: Tue, 20 Nov 2018 20:44:08 +0000 (+0300)
Subject: Do not use spin locks if AO test-and-set is emulated (pthreads)
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=70283bbb4590a386ab11201feb578ed50166f030;p=gc

Do not use spin locks if AO test-and-set is emulated (pthreads)

* include/private/gc_locks.h [BASE_ATOMIC_OPS_EMULATED && GC_PTHREADS]
(USE_PTHREAD_LOCKS): Define.
* include/private/gc_locks.h [BASE_ATOMIC_OPS_EMULATED && GC_PTHREADS]
(USE_SPIN_LOCK): Undefine.
* pthread_support.c [(USE_SPIN_LOCK || !NO_PTHREAD_TRYLOCK)
&& AO_CLEAR] (GC_pause): Do not use AO_compiler_barrier() if
BASE_ATOMIC_OPS_EMULATED.
* pthread_support.c [AO_HAVE_char_load] (is_collecting): Do not use
AO_char_load() if BASE_ATOMIC_OPS_EMULATED.
---

diff --git a/include/private/gc_locks.h b/include/private/gc_locks.h
index f6e45d59..152ad9d3 100644
--- a/include/private/gc_locks.h
+++ b/include/private/gc_locks.h
@@ -54,7 +54,8 @@
 
 #  if (!defined(AO_HAVE_test_and_set_acquire) || defined(GC_RTEMS_PTHREADS) \
        || defined(SN_TARGET_ORBIS) || defined(SN_TARGET_PS3) \
-       || defined(GC_WIN32_THREADS) || defined(LINT2)) && defined(GC_PTHREADS)
+       || defined(GC_WIN32_THREADS) || defined(BASE_ATOMIC_OPS_EMULATED) \
+       || defined(LINT2)) && defined(GC_PTHREADS)
 #    define USE_PTHREAD_LOCKS
 #    undef USE_SPIN_LOCK
 #  endif
diff --git a/pthread_support.c b/pthread_support.c
index 4105077f..61e0a10e 100644
--- a/pthread_support.c
+++ b/pthread_support.c
@@ -1941,7 +1941,7 @@ STATIC void GC_pause(void)
 
     for (i = 0; i < GC_PAUSE_SPIN_CYCLES; ++i) {
         /* Something that's unlikely to be optimized away. */
-#     ifdef AO_CLEAR
+#     if defined(AO_CLEAR) && !defined(BASE_ATOMIC_OPS_EMULATED)
         AO_compiler_barrier();
 #     else
         GC_noop1(i);
@@ -2023,7 +2023,7 @@ STATIC void GC_generic_lock(pthread_mutex_t * lock)
 
 #endif /* !USE_SPIN_LOCK || ... */
 
-#ifdef AO_HAVE_char_load
+#if defined(AO_HAVE_char_load) && !defined(BASE_ATOMIC_OPS_EMULATED)
 # define is_collecting() \
                 ((GC_bool)AO_char_load((unsigned char *)&GC_collecting))
 #else