Implemented pthread spinlocks.

configure.in

@@ -280,6 +280,25 @@ if test x$enable_gcc_atomics = xyes; then
     fi
 fi
 
+# Check for pthread implementation
+AC_MSG_CHECKING(for pthread spinlock)
+have_pthread_spinlock=no
+
+AC_TRY_LINK([
+#include <pthread.h>
+],[
+pthread_spinlock_t a;
+pthread_spin_trylock(&a);
+pthread_spin_unlock(&a);
+],[
+have_pthread_spinlock=yes
+])
+AC_MSG_RESULT($have_pthread_spinlock)
+if test x$have_pthread_spinlock = xyes; then
+    AC_DEFINE(HAVE_PTHREAD_SPINLOCK, 1, [ ])
+fi
+
+
 # Standard C sources
 SOURCES="$SOURCES $srcdir/src/*.c"
 SOURCES="$SOURCES $srcdir/src/atomic/*.c"

include/SDL_config.h.in

@@ -45,6 +45,7 @@
 #undef SIZEOF_VOIDP
 #undef HAVE_GCC_ATOMICS
 #undef HAVE_GCC_SYNC_LOCK_TEST_AND_SET
+#undef HAVE_PTHREAD_SPINLOCK
 
 /* Comment this if you want to build without any C library requirements */
 #undef HAVE_LIBC

src/atomic/SDL_spinlock.c

@@ -77,9 +77,13 @@ SDL_AtomicTryLock(SDL_SpinLock *lock)
         : "=&r" (result) : "r" (1), "r" (lock) : "cc", "memory");
     return (result == 0);
 
-#else
+#elif HAVE_PTHREAD_SPINLOCK
+    /* pthread instructions */
+    return (pthread_spin_trylock(lock) == 0);
+#else	
     /* Need CPU instructions for spinlock here! */
     __need_spinlock_implementation__
+	
 #endif
 }
 
@@ -101,7 +105,10 @@ SDL_AtomicUnlock(SDL_SpinLock *lock)
 
 #elif HAVE_GCC_ATOMICS || HAVE_GCC_SYNC_LOCK_TEST_AND_SET
     __sync_lock_release(lock);
-
+    
+#elif HAVE_PTHREAD_SPINLOCK
+    pthread_spin_unlock(lock);
+	
 #else
     *lock = 0;
 #endif