From: Mukund Sivaraman <muks@isc.org>
Date: Wed, 27 Sep 2017 09:38:06 +0000 (+0530)
Subject: Make isc_refcount_current() atomically read the counter value (#46074)
X-Git-Tag: v9.12.0b1~132
X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=abb8813a3338ee63d28aa14b7dde74892fe1879f;p=thirdparty%2Fbind9.git

Make isc_refcount_current() atomically read the counter value (#46074)
---

diff --git a/CHANGES b/CHANGES
index 5cb3e7252bb..801c6561602 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+4741.	[bug]		Make isc_refcount_current() atomically read the
+			counter value. [RT #46074]
+
 4740.	[cleanup]	Avoid triggering format-truncated warnings. [RT #46107]
 
 4739.	[cleanup]	Address clang static analysis warnings. [RT #45952]
diff --git a/lib/isc/include/isc/refcount.h b/lib/isc/include/isc/refcount.h
index acc99599620..24ad9dae945 100644
--- a/lib/isc/include/isc/refcount.h
+++ b/lib/isc/include/isc/refcount.h
@@ -104,11 +104,13 @@ typedef struct isc_refcount {
 #endif
 } isc_refcount_t;
 
-#define isc_refcount_destroy(rp) REQUIRE((rp)->refs == 0)
-#define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
-
 #if defined(ISC_REFCOUNT_HAVESTDATOMIC)
 
+#define isc_refcount_current(rp)					\
+	((unsigned int)(atomic_load_explicit(&(rp)->refs,		\
+					     memory_order_relaxed)))
+#define isc_refcount_destroy(rp) REQUIRE(isc_refcount_current(rp) == 0)
+
 #define isc_refcount_increment0(rp, tp)				\
 	do {							\
 		unsigned int *_tmp = (unsigned int *)(tp);	\
@@ -143,6 +145,10 @@ typedef struct isc_refcount {
 
 #else /* ISC_REFCOUNT_HAVESTDATOMIC */
 
+#define isc_refcount_current(rp)				\
+	((unsigned int)(isc_atomic_xadd(&(rp)->refs, 0)))
+#define isc_refcount_destroy(rp) REQUIRE(isc_refcount_current(rp) == 0)
+
 #define isc_refcount_increment0(rp, tp)				\
 	do {							\
 		unsigned int *_tmp = (unsigned int *)(tp);	\