From: Francis Deslauriers <francis.deslauriers@efficios.com>
Date: Wed, 8 Mar 2017 16:50:38 +0000 (-0500)
Subject: Fix: atomic_add_unless() returns true/false rather than prior value
X-Git-Tag: v2.10.0-rc1~15
X-Git-Url: http://git.lttng.org/?p=lttng-modules.git;a=commitdiff_plain;h=4c4d77dacf277775cb395190cf827c7f0c226a99

Fix: atomic_add_unless() returns true/false rather than prior value

The previous implementation assumed that `atomic_add_unless` returned
the prior value of the atomic counter when in fact it returned if the
addition was performed (true) or not performed (false).
Since `atomic_add_unless` can not return INT_MAX, the `lttng_kref_get`
always returned that the call was successful.

This issue had a low likelihood of being triggered since the two refcounts
of the counters used with this call are both bounded by the maximum
number of file descriptors on the system.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/wrapper/kref.h b/wrapper/kref.h
index eedefbfe..f30a9aed 100644
--- a/wrapper/kref.h
+++ b/wrapper/kref.h
@@ -36,11 +36,7 @@
  */
 static inline int lttng_kref_get(struct kref *kref)
 {
-	if (atomic_add_unless(&kref->refcount, 1, INT_MAX) != INT_MAX) {
-		return 1;
-	} else {
-		return 0;
-	}
+	return atomic_add_unless(&kref->refcount, 1, INT_MAX);
 }
 
 #endif /* _LTTNG_WRAPPER_KREF_H */