From 908b33644e40083593b56a540210ba2267f3939f Mon Sep 17 00:00:00 2001
From: John Ferlan <jferlan@redhat.com>
Date: Fri, 28 Jul 2017 10:06:55 -0400
Subject: [PATCH] util: Introduce and use virObjectRWLockWrite

Instead of making virObjectLock be the entry point for two
different types of locks, let's create a virObjectRWLockWrite API
which will only handle the virObjectRWLockableClass objects.

Use the new virObjectRWLockWrite for the virdomainobjlist code
in order to handle the Add, Remove, Rename, and Load operations
that need to be very synchronous.

Signed-off-by: John Ferlan <jferlan@redhat.com>
---
 src/conf/virdomainobjlist.c |  8 ++++----
 src/libvirt_private.syms    |  1 +
 src/util/virobject.c        | 33 ++++++++++++++++++++++++++++++++-
 src/util/virobject.h        |  4 ++++
 4 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/src/conf/virdomainobjlist.c b/src/conf/virdomainobjlist.c
index 9bc6603353..573032f14b 100644
--- a/src/conf/virdomainobjlist.c
+++ b/src/conf/virdomainobjlist.c
@@ -327,7 +327,7 @@ virDomainObjPtr virDomainObjListAdd(virDomainObjListPtr doms,
 {
     virDomainObjPtr ret;
 
-    virObjectLock(doms);
+    virObjectRWLockWrite(doms);
     ret = virDomainObjListAddLocked(doms, def, xmlopt, flags, oldDef);
     virObjectUnlock(doms);
     return ret;
@@ -349,7 +349,7 @@ void virDomainObjListRemove(virDomainObjListPtr doms,
     virObjectRef(dom);
     virObjectUnlock(dom);
 
-    virObjectLock(doms);
+    virObjectRWLockWrite(doms);
     virObjectLock(dom);
     virHashRemoveEntry(doms->objs, uuidstr);
     virHashRemoveEntry(doms->objsName, dom->def->name);
@@ -394,7 +394,7 @@ virDomainObjListRename(virDomainObjListPtr doms,
      * hold a lock on dom but not refcount it. */
     virObjectRef(dom);
     virObjectUnlock(dom);
-    virObjectLock(doms);
+    virObjectRWLockWrite(doms);
     virObjectLock(dom);
     virObjectUnref(dom);
 
@@ -573,7 +573,7 @@ virDomainObjListLoadAllConfigs(virDomainObjListPtr doms,
     if ((rc = virDirOpenIfExists(&dir, configDir)) <= 0)
         return rc;
 
-    virObjectLock(doms);
+    virObjectRWLockWrite(doms);
 
     while ((ret = virDirRead(dir, &entry, configDir)) > 0) {
         virDomainObjPtr dom;
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index b5fc31a64f..01a2f3a814 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2312,6 +2312,7 @@ virObjectNew;
 virObjectRef;
 virObjectRWLockableNew;
 virObjectRWLockRead;
+virObjectRWLockWrite;
 virObjectUnlock;
 virObjectUnref;
 
diff --git a/src/util/virobject.c b/src/util/virobject.c
index b97f251afd..f49af62c81 100644
--- a/src/util/virobject.c
+++ b/src/util/virobject.c
@@ -429,12 +429,43 @@ virObjectRWLockRead(void *anyobj)
 }
 
 
+/**
+ * virObjectRWLockWrite:
+ * @anyobj: any instance of virObjectRWLockable
+ *
+ * Acquire a write lock on @anyobj. The lock must be
+ * released by virObjectUnlock.
+ *
+ * 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.
+ *
+ * NB: It's possible to return without the lock if
+ *     @anyobj was invalid - this has been considered
+ *     a programming error rather than something that
+ *     should be checked.
+ */
+void
+virObjectRWLockWrite(void *anyobj)
+{
+    if (virObjectIsClass(anyobj, virObjectRWLockableClass)) {
+        virObjectRWLockablePtr obj = anyobj;
+        virRWLockWrite(&obj->lock);
+    } else {
+        virObjectPtr obj = anyobj;
+        VIR_WARN("Object %p (%s) is not a virObjectRWLockable instance",
+                 anyobj, obj ? obj->klass->name : "(unknown)");
+    }
+}
+
+
 /**
  * virObjectUnlock:
  * @anyobj: any instance of virObjectLockable or virObjectRWLockable
  *
  * Release a lock on @anyobj. The lock must have been acquired by
- * virObjectLock or virObjectRWLockRead.
+ * virObjectLock, virObjectRWLockRead, or virObjectRWLockWrite.
  */
 void
 virObjectUnlock(void *anyobj)
diff --git a/src/util/virobject.h b/src/util/virobject.h
index e7ca983921..24ee6dda8b 100644
--- a/src/util/virobject.h
+++ b/src/util/virobject.h
@@ -128,6 +128,10 @@ void
 virObjectRWLockRead(void *lockableobj)
     ATTRIBUTE_NONNULL(1);
 
+void
+virObjectRWLockWrite(void *lockableobj)
+    ATTRIBUTE_NONNULL(1);
+
 void
 virObjectUnlock(void *lockableobj)
     ATTRIBUTE_NONNULL(1);