From f8598074c9df8821312f2c4a7cea9ba772625f82 Mon Sep 17 00:00:00 2001
From: Ted Unangst <tedu@cvs.openbsd.org>
Date: Sat, 3 Dec 2005 18:16:20 +0000
Subject: add userland thread library.  incomplete, but functional

---
 lib/librthread/arch/i386/_atomic_lock.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 lib/librthread/arch/i386/_atomic_lock.c

(limited to 'lib/librthread/arch/i386/_atomic_lock.c')

diff --git a/lib/librthread/arch/i386/_atomic_lock.c b/lib/librthread/arch/i386/_atomic_lock.c
new file mode 100644
index 00000000000..7b9b46a73c7
--- /dev/null
+++ b/lib/librthread/arch/i386/_atomic_lock.c
@@ -0,0 +1,25 @@
+/*	$OpenBSD: _atomic_lock.c,v 1.1 2005/12/03 18:16:19 tedu Exp $	*/
+/* David Leonard, <d@csee.uq.edu.au>. Public domain. */
+
+/*
+ * Atomic lock for i386
+ */
+
+#include <machine/spinlock.h>
+
+int
+_atomic_lock(register volatile _spinlock_lock_t *lock)
+{
+	register _spinlock_lock_t old;
+
+	/*
+	 * Use the eXCHanGe instruction to swap the lock value with
+	 * a local variable containing the locked state.
+	 */
+	old = _SPINLOCK_LOCKED;
+	__asm__("xchg %0,%1"
+		: "=r" (old), "=m" (*lock)
+		: "0"  (old), "1"  (*lock));
+
+	return (old != _SPINLOCK_UNLOCKED);
+}
-- 
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