From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 21 Jan 2016 16:45:58 +0000 (-0500)
Subject: urcu_ref_get_safe: introduce new API
X-Git-Tag: v0.10.0~55
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=8b4b5a1a5f8587cb995391e4f49d03674ec60c0c;p=urcu.git

urcu_ref_get_safe: introduce new API

Add a urcu_ref_get_safe API, which returns a boolean. It takes the value
"false" if a LONG_MAX overflow would occur (get is not performed in this
case), or true otherwise.

It warns the user (at compile-time) if the return value is unchecked.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/urcu/ref.h b/urcu/ref.h
index 2b803e5..e546da5 100644
--- a/urcu/ref.h
+++ b/urcu/ref.h
@@ -34,24 +34,31 @@ static inline void urcu_ref_init(struct urcu_ref *ref)
 	urcu_ref_set(ref, 1);
 }
 
-static inline void urcu_ref_get(struct urcu_ref *ref)
+static inline bool  __attribute__((warn_unused_result))
+		urcu_ref_get_safe(struct urcu_ref *ref)
 {
 	long old, _new, res;
 
 	old = uatomic_read(&ref->refcount);
 	for (;;) {
 		if (old == LONG_MAX) {
-			abort();
+			return false;	/* Failure. */
 		}
 		_new = old + 1;
 		res = uatomic_cmpxchg(&ref->refcount, old, _new);
 		if (res == old) {
-			return;
+			return true;	/* Success. */
 		}
 		old = res;
 	}
 }
 
+static inline void urcu_ref_get(struct urcu_ref *ref)
+{
+	if (!urcu_ref_get_safe(ref))
+		abort();
+}
+
 static inline void urcu_ref_put(struct urcu_ref *ref,
 				void (*release)(struct urcu_ref *))
 {