Implement atomic_decrement with LL-SC on ARM/ARM64

1 files changed, 19 insertions, 7 deletions

diff --git a/src/threadpool-pthreads.c b/src/threadpool-pthreads.c
index 07c47f0..934e5e7 100644
--- a/src/threadpool-pthreads.c
+++ b/src/threadpool-pthreads.c
@@ -289,16 +289,28 @@ static void wait_worker_threads(struct pthreadpool* threadpool) {
 }
 
 inline static bool atomic_decrement(pthreadpool_atomic_size_t* value) {
-	size_t actual_value = pthreadpool_load_relaxed_size_t(value);
-	if (actual_value == 0) {
-		return false;
-	}
-	while (!pthreadpool_compare_exchange_weak_relaxed_size_t(value, &actual_value, actual_value - 1)) {
+	#if defined(__clang__) && (defined(__arm__) || defined(__aarch64__))
+		size_t actual_value;
+		do {
+			actual_value = __builtin_arm_ldrex((const volatile size_t*) value);
+			if (actual_value == 0) {
+				__builtin_arm_clrex();
+				return false;
+			}
+		} while (__builtin_arm_strex(actual_value - 1, (volatile size_t*) value) != 0);
+		return true;
+	#else
+		size_t actual_value = pthreadpool_load_relaxed_size_t(value);
 		if (actual_value == 0) {
 			return false;
 		}
-	}
-	return true;
+		while (!pthreadpool_compare_exchange_weak_relaxed_size_t(value, &actual_value, actual_value - 1)) {
+			if (actual_value == 0) {
+				return false;
+			}
+		}
+		return true;
+	#endif
 }
 
 inline static size_t modulo_decrement(uint32_t i, uint32_t n) {