patch-2.4.19 linux-2.4.19/arch/ppc64/lib/dec_and_lock.c

• Lines: 39
• Date: Fri Aug 2 17:39:43 2002
• Orig file: linux-2.4.18/arch/ppc64/lib/dec_and_lock.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.18/arch/ppc64/lib/dec_and_lock.c linux-2.4.19/arch/ppc64/lib/dec_and_lock.c
@@ -0,0 +1,38 @@
+/*
+ * ppc64 version of atomic_dec_and_lock() using cmpxchg
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/spinlock.h>
+#include <asm/system.h>
+#include <asm/atomic.h>
+
+int atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+	int counter;
+	int newcount;
+
+repeat:
+	counter = atomic_read(atomic);
+	newcount = counter-1;
+
+	if (!newcount)
+		goto slow_path;
+
+	newcount = cmpxchg(&atomic->counter, counter, newcount);
+
+	if (newcount != counter)
+		goto repeat;
+	return 0;
+
+slow_path:
+	spin_lock(lock);
+	if (atomic_dec_and_test(atomic))
+		return 1;
+	spin_unlock(lock);
+	return 0;
+}