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authorAndreas Gruenbacher <agruenba@redhat.com>2018-03-29 08:07:46 +0100
committerBob Peterson <rpeterso@redhat.com>2018-04-12 09:41:19 -0700
commit450b1f6f56350c630e795f240dc5a77aa8aa2419 (patch)
treed6809eb52cf4317836ddc5e51f582a72bb2a9c9a
parente241e3f2bf975788a1b70dff2eb5180ca395b28e (diff)
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lockref: Add lockref_put_not_zero
Put a lockref unless the lockref is dead or its count would become zero. This is the same as lockref_put_or_lock except that the lock is never left held. Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com> Signed-off-by: Bob Peterson <rpeterso@redhat.com>
-rw-r--r--include/linux/lockref.h1
-rw-r--r--lib/lockref.c28
2 files changed, 29 insertions, 0 deletions
diff --git a/include/linux/lockref.h b/include/linux/lockref.h
index 2eac32095113..99f17cc8e163 100644
--- a/include/linux/lockref.h
+++ b/include/linux/lockref.h
@@ -37,6 +37,7 @@ struct lockref {
extern void lockref_get(struct lockref *);
extern int lockref_put_return(struct lockref *);
extern int lockref_get_not_zero(struct lockref *);
+extern int lockref_put_not_zero(struct lockref *);
extern int lockref_get_or_lock(struct lockref *);
extern int lockref_put_or_lock(struct lockref *);
diff --git a/lib/lockref.c b/lib/lockref.c
index 47169ed7e964..3d468b53d4c9 100644
--- a/lib/lockref.c
+++ b/lib/lockref.c
@@ -81,6 +81,34 @@ int lockref_get_not_zero(struct lockref *lockref)
EXPORT_SYMBOL(lockref_get_not_zero);
/**
+ * lockref_put_not_zero - Decrements count unless count <= 1 before decrement
+ * @lockref: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count would become zero
+ */
+int lockref_put_not_zero(struct lockref *lockref)
+{
+ int retval;
+
+ CMPXCHG_LOOP(
+ new.count--;
+ if (old.count <= 1)
+ return 0;
+ ,
+ return 1;
+ );
+
+ spin_lock(&lockref->lock);
+ retval = 0;
+ if (lockref->count > 1) {
+ lockref->count--;
+ retval = 1;
+ }
+ spin_unlock(&lockref->lock);
+ return retval;
+}
+EXPORT_SYMBOL(lockref_put_not_zero);
+
+/**
* lockref_get_or_lock - Increments count unless the count is 0 or dead
* @lockref: pointer to lockref structure
* Return: 1 if count updated successfully or 0 if count was zero