From: Ricardo M. Correia <ricardo.correia@oracle.com>
Date: Fri, 17 Sep 2010 23:03:15 +0000 (-0700)
Subject: atomic_*_*_nv() functions need to return the new value atomically.
X-Git-Tag: zfs-0.8.0-rc1~152^2~528
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a68d91d770c0d4b8b72d9d07e65a79f3f99f03c6;p=zfs

atomic_*_*_nv() functions need to return the new value atomically.

A local variable must be used for the return value to avoid a
potential race once the spin lock is dropped.

Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
---

diff --git a/include/sys/atomic.h b/include/sys/atomic.h
index 9348ab97e..1d1173894 100644
--- a/include/sys/atomic.h
+++ b/include/sys/atomic.h
@@ -93,41 +93,51 @@ atomic_sub_32(volatile uint32_t *target, int32_t delta)
 static __inline__ uint32_t
 atomic_inc_32_nv(volatile uint32_t *target)
 {
+	uint32_t nv;
+
 	spin_lock(&atomic32_lock);
-	(*target)++;
+	nv = ++(*target);
 	spin_unlock(&atomic32_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint32_t
 atomic_dec_32_nv(volatile uint32_t *target)
 {
+	uint32_t nv;
+
 	spin_lock(&atomic32_lock);
-	(*target)--;
+	nv = --(*target);
 	spin_unlock(&atomic32_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint32_t
 atomic_add_32_nv(volatile uint32_t *target, uint32_t delta)
 {
+	uint32_t nv;
+
 	spin_lock(&atomic32_lock);
 	*target += delta;
+	nv = *target;
 	spin_unlock(&atomic32_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint32_t
 atomic_sub_32_nv(volatile uint32_t *target, uint32_t delta)
 {
+	uint32_t nv;
+
 	spin_lock(&atomic32_lock);
 	*target -= delta;
+	nv = *target;
 	spin_unlock(&atomic32_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint32_t
@@ -181,41 +191,51 @@ atomic_sub_64(volatile uint64_t *target, uint64_t delta)
 static __inline__ uint64_t
 atomic_inc_64_nv(volatile uint64_t *target)
 {
+	uint64_t nv;
+
 	spin_lock(&atomic64_lock);
-	(*target)++;
+	nv = ++(*target);
 	spin_unlock(&atomic64_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint64_t
 atomic_dec_64_nv(volatile uint64_t *target)
 {
+	uint64_t nv;
+
 	spin_lock(&atomic64_lock);
-	(*target)--;
+	nv = --(*target);
 	spin_unlock(&atomic64_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint64_t
 atomic_add_64_nv(volatile uint64_t *target, uint64_t delta)
 {
+	uint64_t nv;
+
 	spin_lock(&atomic64_lock);
 	*target += delta;
+	nv = *target;
 	spin_unlock(&atomic64_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint64_t
 atomic_sub_64_nv(volatile uint64_t *target, uint64_t delta)
 {
+	uint64_t nv;
+
 	spin_lock(&atomic64_lock);
 	*target -= delta;
+	nv = *target;
 	spin_unlock(&atomic64_lock);
 
-	return *target;
+	return nv;
 }
 
 static __inline__ uint64_t