[libvirt] [[RFC] 1/8] Introduce virObjectTrylock()
This is a wrapper function that:
(1) Attempts to take a lock on the object.
(2) gracefully returns if the object is already locked.
Signed-off-by: Prerna Saxena <saxenap.ltc(a)gmail.com>
---
src/libvirt_private.syms | 1 +
src/util/virobject.c | 26 ++++++++++++++++++++++++++
src/util/virobject.h | 4 ++++
src/util/virthread.c | 5 +++++
src/util/virthread.h | 1 +
5 files changed, 37 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 9243c55..c0ab8b5 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2362,6 +2362,7 @@ virObjectRWLockableNew;
virObjectRWLockRead;
virObjectRWLockWrite;
virObjectRWUnlock;
+virObjectTrylock;
virObjectUnlock;
virObjectUnref;
diff --git a/src/util/virobject.c b/src/util/virobject.c
index cfa821c..796ea06 100644
--- a/src/util/virobject.c
+++ b/src/util/virobject.c
@@ -495,6 +495,32 @@ virObjectRWLockWrite(void *anyobj)
/**
+ * virObjectTrylock:
+ * @anyobj: any instance of virObjectLockable or virObjectRWLockable
+ *
+ * Attempt to acquire a lock on @anyobj. The lock must be released by
+ * virObjectUnlock.
+ * Returns:
+ * 0: If the lock was successfully taken.
+ * errno : Indicates error.
+ *
+ * The caller is expected to have acquired a reference
+ * on the object before locking it (eg virObjectRef).
+ * The object must be unlocked before releasing this
+ * reference.
+ */
+int
+virObjectTrylock(void *anyobj)
+{
+ virObjectLockablePtr obj = virObjectGetLockableObj(anyobj);
+
+ if (!obj)
+ return -1;
+
+ return virMutexTrylock(&obj->lock);
+}
+
+/**
* virObjectUnlock:
* @anyobj: any instance of virObjectLockable
*
diff --git a/src/util/virobject.h b/src/util/virobject.h
index ac6cf22..402ea32 100644
--- a/src/util/virobject.h
+++ b/src/util/virobject.h
@@ -124,6 +124,10 @@ void
virObjectLock(void *lockableobj)
ATTRIBUTE_NONNULL(1);
+int
+virObjectTrylock(void *lockableobj)
+ ATTRIBUTE_NONNULL(1);
+
void
virObjectRWLockRead(void *lockableobj)
ATTRIBUTE_NONNULL(1);
diff --git a/src/util/virthread.c b/src/util/virthread.c
index 6c49515..07b7a3f 100644
--- a/src/util/virthread.c
+++ b/src/util/virthread.c
@@ -89,6 +89,11 @@ void virMutexLock(virMutexPtr m)
pthread_mutex_lock(&m->lock);
}
+int virMutexTrylock(virMutexPtr m)
+{
+ return pthread_mutex_trylock(&m->lock);
+}
+
void virMutexUnlock(virMutexPtr m)
{
pthread_mutex_unlock(&m->lock);
diff --git a/src/util/virthread.h b/src/util/virthread.h
index e466d9b..8e3da2c 100644
--- a/src/util/virthread.h
+++ b/src/util/virthread.h
@@ -132,6 +132,7 @@ int virMutexInitRecursive(virMutexPtr m) ATTRIBUTE_RETURN_CHECK;
void virMutexDestroy(virMutexPtr m);
void virMutexLock(virMutexPtr m);
+int virMutexTrylock(virMutexPtr m);
void virMutexUnlock(virMutexPtr m);
--
2.9.5