lockless get_write_access/deny_write_access

new helpers: atomic_inc_unless_negative()/atomic_dec_unless_positive()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 26 insertions, 0 deletions

diff --git a/include/linux/atomic.h b/include/linux/atomic.h
index ee456c79b0e6..bc6615d4132b 100644
--- a/include/linux/atomic.h
+++ b/include/linux/atomic.h
@@ -34,6 +34,32 @@ static inline int atomic_inc_not_zero_hint(atomic_t *v, int hint)
 }
 #endif
 
+#ifndef atomic_inc_unless_negative
+static inline int atomic_inc_unless_negative(atomic_t *p)
+{
+        int v, v1;
+        for (v = 0; v >= 0; v = v1) {
+                v1 = atomic_cmpxchg(p, v, v + 1);
+                if (likely(v1 == v))
+                        return 1;
+        }
+        return 0;
+}
+#endif
+
+#ifndef atomic_dec_unless_positive
+static inline int atomic_dec_unless_positive(atomic_t *p)
+{
+        int v, v1;
+        for (v = 0; v <= 0; v = v1) {
+                v1 = atomic_cmpxchg(p, v, v - 1);
+                if (likely(v1 == v))
+                        return 1;
+        }
+        return 0;
+}
+#endif
+
 #ifndef CONFIG_ARCH_HAS_ATOMIC_OR
 static inline void atomic_or(int i, atomic_t *v)
 {