gcc says

  spinlock.c:35: warning: matching constraint does not allow a register

Update the asm to match glibc.

libpthread/linuxthreads/spinlock.c

@@ -32,7 +32,7 @@ static inline void __pthread_release(int * spinlock)
 {
   WRITE_MEMORY_BARRIER();
   *spinlock = __LT_SPINLOCK_INIT;
-  __asm __volatile ("" : "=m" (*spinlock) : "0" (*spinlock));
+  __asm __volatile ("" : "=m" (*spinlock) : "m" (*spinlock));
 }