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Date:      Mon, 22 Oct 2018 16:21:50 +0000 (UTC)
From:      Hans Petter Selasky <hselasky@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r339600 - head/sys/sys
Message-ID:  <201810221621.w9MGLoxJ068909@repo.freebsd.org>
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Author: hselasky
Date: Mon Oct 22 16:21:50 2018
New Revision: 339600
URL: https://svnweb.freebsd.org/changeset/base/339600

Log:
  Make sure returned value is checked and assert a valid refcount.
  While at it fix a print: Unsigned types cannot be negative.
  
  Reviewed by:		kib, mjg
  Differential revision:	https://reviews.freebsd.org/D17616
  MFC after:		1 week
  Sponsored by:		Mellanox Technologies

Modified:
  head/sys/sys/refcount.h

Modified: head/sys/sys/refcount.h
==============================================================================
--- head/sys/sys/refcount.h	Mon Oct 22 16:16:42 2018	(r339599)
+++ head/sys/sys/refcount.h	Mon Oct 22 16:21:50 2018	(r339600)
@@ -62,7 +62,7 @@ refcount_release(volatile u_int *count)
 
 	atomic_thread_fence_rel();
 	old = atomic_fetchadd_int(count, -1);
-	KASSERT(old > 0, ("negative refcount %p", count));
+	KASSERT(old > 0, ("refcount %p is zero", count));
 	if (old > 1)
 		return (0);
 
@@ -77,15 +77,19 @@ refcount_release(volatile u_int *count)
 }
 
 /*
+ * This functions returns non-zero if the refcount was
+ * incremented. Else zero is returned.
+ *
  * A temporary hack until refcount_* APIs are sorted out.
  */
-static __inline int
+static __inline __result_use_check int
 refcount_acquire_if_not_zero(volatile u_int *count)
 {
 	u_int old;
 
 	old = *count;
 	for (;;) {
+		KASSERT(old < UINT_MAX, ("refcount %p overflowed", count));
 		if (old == 0)
 			return (0);
 		if (atomic_fcmpset_int(count, &old, old + 1))
@@ -93,13 +97,14 @@ refcount_acquire_if_not_zero(volatile u_int *count)
 	}
 }
 
-static __inline int
+static __inline __result_use_check int
 refcount_release_if_not_last(volatile u_int *count)
 {
 	u_int old;
 
 	old = *count;
 	for (;;) {
+		KASSERT(old > 0, ("refcount %p is zero", count));
 		if (old == 1)
 			return (0);
 		if (atomic_fcmpset_int(count, &old, old - 1))

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