Index: src/atomic.h
==================================================================
--- src/atomic.h
+++ src/atomic.h
@@ -12,15 +12,28 @@
 #import "objfw-defs.h"
 
 #if !defined(OF_THREADS)
 # define of_atomic_inc32(p) ++(*p)
 # define of_atomic_dec32(p) --(*p)
+# define of_atomic_cmpswap32(p, o, n) (*p == o ? ((*p = n) ? 1 : 1) : 0)
 #elif defined(OF_HAVE_GCC_ATOMIC_OPS)
 # define of_atomic_inc32(p) __sync_add_and_fetch(p, 1)
 # define of_atomic_dec32(p) __sync_sub_and_fetch(p, 1)
+# define of_atomic_cmpswap32(p, o, n) __sync_bool_compare_and_swap(p, o, n)
 #elif defined(OF_HAVE_LIBKERN_OSATOMIC_H)
 # include <libkern/OSAtomic.h>
 # define of_atomic_inc32(p) OSAtomicIncrement32Barrier((int32_t*)(p))
 # define of_atomic_dec32(p) OSAtomicDecrement32Barrier((int32_t*)(p))
+# define of_atomic_cmpswap32(p, o, n) \
+	OSAtomicCompareAndSwap32Barrier(o, n, (int32_t*)p)
 #else
 # error No atomic operations available!
 #endif
+
+typedef int32_t of_spinlock_t;
+#ifdef OF_THREADS
+# define of_spinlock_lock(s) while (!of_atomic_cmpswap32(&s, 0, 1));
+# define of_spinlock_unlock(s) s = 0
+#else
+# define of_spinlock_lock(s)
+# define of_spinlock_unlock(s)
+#endif