X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=lib%2Fdec_and_lock.c;h=305a9663aee39aba26532082319433e0a4e9ae33;hb=5fadd053d9bb4345ec6f405d24db4e7eb49cf81e;hp=2377af057d099ebd628bd9f7039cd4f54c9bf229;hpb=aa7c3a119a6202b758a669cde9e3829ced64a13f;p=linux-2.6

diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index 2377af057d..305a9663ae 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -1,7 +1,41 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <asm/atomic.h>
+#include <asm/system.h>
 
+#ifdef __HAVE_ARCH_CMPXCHG
+/*
+ * This is an implementation of the notion of "decrement a
+ * reference count, and return locked if it decremented to zero".
+ *
+ * This implementation can be used on any architecture that
+ * has a cmpxchg, and where atomic->value is an int holding
+ * the value of the atomic (i.e. the high bits aren't used
+ * for a lock or anything like that).
+ */
+int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
+{
+	int counter;
+	int newcount;
+
+	for (;;) {
+		counter = atomic_read(atomic);
+		newcount = counter - 1;
+		if (!newcount)
+			break;		/* do it the slow way */
+
+		newcount = cmpxchg(&atomic->counter, counter, newcount);
+		if (newcount == counter)
+			return 0;
+	}
+
+	spin_lock(lock);
+	if (atomic_dec_and_test(atomic))
+		return 1;
+	spin_unlock(lock);
+	return 0;
+}
+#else
 /*
  * This is an architecture-neutral, but slow,
  * implementation of the notion of "decrement
@@ -33,5 +67,6 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
 	spin_unlock(lock);
 	return 0;
 }
+#endif
 
 EXPORT_SYMBOL(_atomic_dec_and_lock);