diff --git a/libraries/wutnewlib/wut_lock.c b/libraries/wutnewlib/wut_lock.c
index 0da87d1c3..b16987a7a 100644
--- a/libraries/wutnewlib/wut_lock.c
+++ b/libraries/wutnewlib/wut_lock.c
@@ -1,12 +1,12 @@
 #include "wut_newlib.h"
 
 #include <coreinit/mutex.h>
-#include <malloc.h>
+#include <coreinit/atomic.h>
 
 #define MAX_LOCKS 16
 
 static OSMutex sLibcLocks[MAX_LOCKS];
-static uint32_t sLibcLockUsedMask = 0;
+static volatile uint32_t sLibcLockUsedMask = 0;
 
 static inline bool
 __wut_is_lock_valid(int *lock)
@@ -24,12 +24,12 @@ __wut_lock_init(int *lock,
 
    int slot;
    uint32_t new_mask;
-   uint32_t cur_mask = __atomic_load_n(&sLibcLockUsedMask, __ATOMIC_SEQ_CST);
+   uint32_t cur_mask = sLibcLockUsedMask;
    do {
       slot = __builtin_ffs(~cur_mask)-1;
       if (slot < 0 || slot >= MAX_LOCKS) break;
       new_mask = cur_mask | (1U << slot);
-   } while (!__atomic_compare_exchange_n(&sLibcLockUsedMask, &cur_mask, new_mask, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST));
+   } while (!OSCompareAndSwapAtomicEx(&sLibcLockUsedMask, cur_mask, new_mask, &cur_mask));
 
    if (slot < 0 || slot >= MAX_LOCKS) {
       return -1;
@@ -48,10 +48,10 @@ __wut_lock_close(int *lock)
    }
 
    uint32_t new_mask;
-   uint32_t cur_mask = __atomic_load_n(&sLibcLockUsedMask, __ATOMIC_SEQ_CST);
+   uint32_t cur_mask = sLibcLockUsedMask;
    do {
       new_mask = cur_mask &~ (1U << *lock);
-   } while (!__atomic_compare_exchange_n(&sLibcLockUsedMask, &cur_mask, new_mask, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST));
+   } while (!OSCompareAndSwapAtomicEx(&sLibcLockUsedMask, cur_mask, new_mask, &cur_mask));
 
    *lock = -1;
    return 0;
diff --git a/libraries/wutnewlib/wut_sbrk.c b/libraries/wutnewlib/wut_sbrk.c
index e9d11c8e4..2226f2584 100644
--- a/libraries/wutnewlib/wut_sbrk.c
+++ b/libraries/wutnewlib/wut_sbrk.c
@@ -14,17 +14,17 @@ void *
 __wut_sbrk_r(struct _reent *r,
              ptrdiff_t incr)
 {
-   uint32_t oldSize, newSize;
+   uint32_t newSize;
+   uint32_t oldSize = sHeapSize;
 
    do {
-      oldSize = sHeapSize;
       newSize = oldSize + incr;
 
       if (newSize > sHeapMaxSize) {
          r->_errno = ENOMEM;
          return (void *)-1;
       }
-   } while (!OSCompareAndSwapAtomic(&sHeapSize, oldSize, newSize));
+   } while (!OSCompareAndSwapAtomicEx(&sHeapSize, oldSize, newSize, &oldSize));
 
    return ((uint8_t *)sHeapBase) + oldSize;
 }
diff --git a/libraries/wutstdc++/wut_gthread_once.cpp b/libraries/wutstdc++/wut_gthread_once.cpp
index 5e7a03c57..52a2f4eb2 100644
--- a/libraries/wutstdc++/wut_gthread_once.cpp
+++ b/libraries/wutstdc++/wut_gthread_once.cpp
@@ -11,9 +11,8 @@ __wut_once(__wut_once_t *once,
                                 __WUT_ONCE_VALUE_STARTED,
                                 &value)) {
       func();
-      OSCompareAndSwapAtomic(once,
-                             __WUT_ONCE_VALUE_STARTED,
-                             __WUT_ONCE_VALUE_DONE);
+      OSSwapAtomic(once,
+                   __WUT_ONCE_VALUE_DONE);
    } else if (value != __WUT_ONCE_VALUE_DONE) {
       while (!OSCompareAndSwapAtomic(once,
                                      __WUT_ONCE_VALUE_DONE,