Move atomic_lock code from asm to C with inline asm;

Add m68k, mips and sparc. (needs more careful checking)
Add 'slow_atomic_lock' for crippled archs.

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/libc_r/arch/i386/_atomic_lock.c b/lib/libc_r/arch/i386/_atomic_lock.c
new file mode 100644
index 00000000000..609dc42fb01
--- /dev/null
+++ b/lib/libc_r/arch/i386/_atomic_lock.c
@@ -0,0 +1,26 @@
+/*	$OpenBSD: _atomic_lock.c,v 1.1 1998/11/20 11:15:36 d Exp $	*/
+/*
+ * Atomic lock aquire for i386.
+ */
+
+#include "spinlock.h"
+
+register_t
+_atomic_lock(volatile register_t *lock)
+{
+	register_t old;
+
+	/*
+	 * Use the eXCHanGe instruction to swap the lock value with
+	 * a local variable containg '1' (the locked state).
+	 */
+	old = 1;
+	__asm__("xchg %0, %1"
+		: "=r" (old), "=m" (*lock) : "0"(old), "1" (*lock)  );
+	/*
+	 * So now there is a 1 in *lock and 'old' contains what
+	 * used to be in the lock. We return 0 if the lock was acquired,
+	 * (ie its old value was 0) or 1 otherwise.
+	 */
+	return old;
+}