[libvirt] [PATCH] event: don't overwrite registration error message

[Eric Blake]

Prior to this patch, an attempt to register an event without an
event loop started results in the vague:

libvirt: Remote Driver error : adding cb to list

Now it gives the much nicer:

libvirt:  error : internal error: could not initialize domain event timer

This also avoids hiding other reasonable error messages, such as
attempts to register a duplicate callback or OOM errors.

Also, document the event loop usage requirement, since that was how
I ran into the issue.

* src/remote/remote_driver.c (remoteConnectNetworkEventRegisterAny)
(remoteConnectDomainEventRegister)
(remoteConnectDomainEventRegisterAny): Preserve more detailed error.
* src/libvirt.c (virConnectDomainEventRegister)
(virConnectDomainEventRegisterAny)
(virConnectNetworkEventRegisterAny): Document event loop requirement.

Signed-off-by: Eric Blake <eblake at redhat.com>
---
 src/libvirt.c              | 24 +++++++++++++++---------
 src/remote/remote_driver.c | 12 +++---------
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/src/libvirt.c b/src/libvirt.c
index 90773bb..f8b11b3 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -14829,11 +14829,13 @@ error:
  * @freecb: optional function to deallocate opaque when not used anymore
  *
  * Adds a callback to receive notifications of domain lifecycle events
- * occurring on a connection
+ * occurring on a connection.  This function requires that an event loop
+ * has been previously registered with virEventRegisterImpl() or
+ * virEventRegisterDefaultImpl().
  *
  * Use of this method is no longer recommended. Instead applications
  * should try virConnectDomainEventRegisterAny() which has a more flexible
- * API contract
+ * API contract.
  *
  * The virDomainPtr object handle passed into the callback upon delivery
  * of an event is only valid for the duration of execution of the callback.
@@ -14842,7 +14844,7 @@ error:
  * The reference can be released once the object is no longer required
  * by calling virDomainFree.
  *
- * Returns 0 on success, -1 on failure
+ * Returns 0 on success, -1 on failure.
  */
 int
 virConnectDomainEventRegister(virConnectPtr conn,
@@ -17541,10 +17543,12 @@ error:
  * @freecb: optional function to deallocate opaque when not used anymore
  *
  * Adds a callback to receive notifications of arbitrary domain events
- * occurring on a domain.
+ * occurring on a domain.  This function requires that an event loop
+ * has been previously registered with virEventRegisterImpl() or
+ * virEventRegisterDefaultImpl().
  *
  * If @dom is NULL, then events will be monitored for any domain. If @dom
- * is non-NULL, then only the specific domain will be monitored
+ * is non-NULL, then only the specific domain will be monitored.
  *
  * Most types of event have a callback providing a custom set of parameters
  * for the event. When registering an event, it is thus necessary to use
@@ -17562,7 +17566,7 @@ error:
  * for the callback. To unregister a callback, this callback ID should
  * be passed to the virConnectDomainEventDeregisterAny() method.
  *
- * Returns a callback identifier on success, -1 on failure
+ * Returns a callback identifier on success, -1 on failure.
  */
 int
 virConnectDomainEventRegisterAny(virConnectPtr conn,
@@ -17657,10 +17661,12 @@ error:
  * @freecb: optional function to deallocate opaque when not used anymore
  *
  * Adds a callback to receive notifications of arbitrary network events
- * occurring on a network.
+ * occurring on a network.  This function requires that an event loop
+ * has been previously registered with virEventRegisterImpl() or
+ * virEventRegisterDefaultImpl().
  *
  * If @net is NULL, then events will be monitored for any network. If @net
- * is non-NULL, then only the specific network will be monitored
+ * is non-NULL, then only the specific network will be monitored.
  *
  * Most types of event have a callback providing a custom set of parameters
  * for the event. When registering an event, it is thus necessary to use
@@ -17678,7 +17684,7 @@ error:
  * for the callback. To unregister a callback, this callback ID should
  * be passed to the virConnectNetworkEventDeregisterAny() method.
  *
- * Returns a callback identifier on success, -1 on failure
+ * Returns a callback identifier on success, -1 on failure.
  */
 int
 virConnectNetworkEventRegisterAny(virConnectPtr conn,
diff --git a/src/remote/remote_driver.c b/src/remote/remote_driver.c
index be282d6..11785e2 100644
--- a/src/remote/remote_driver.c
+++ b/src/remote/remote_driver.c
@@ -2932,10 +2932,8 @@ remoteConnectNetworkEventRegisterAny(virConnectPtr conn,
                                                 net, eventID,
                                                 VIR_OBJECT_EVENT_CALLBACK(callback),
                                                 opaque, freecb,
-                                                &callbackID)) < 0) {
-        virReportError(VIR_ERR_RPC, "%s", _("adding cb to list"));
+                                                &callbackID)) < 0)
         goto done;
-    }

     /* If this is the first callback for this eventID, we need to enable
      * events on the server */
@@ -4424,10 +4422,8 @@ static int remoteConnectDomainEventRegister(virConnectPtr conn,
     remoteDriverLock(priv);

     if ((count = virDomainEventStateRegister(conn, priv->domainEventState,
-                                             callback, opaque, freecb)) < 0) {
-         virReportError(VIR_ERR_RPC, "%s", _("adding cb to list"));
+                                             callback, opaque, freecb)) < 0)
          goto done;
-    }

     if (count == 1) {
         /* Tell the server when we are the first callback deregistering */
@@ -5234,10 +5230,8 @@ static int remoteConnectDomainEventRegisterAny(virConnectPtr conn,
                                                priv->domainEventState,
                                                dom, eventID,
                                                callback, opaque, freecb,
-                                               &callbackID)) < 0) {
-        virReportError(VIR_ERR_RPC, "%s", _("adding cb to list"));
+                                               &callbackID)) < 0)
         goto done;
-    }

     /* If this is the first callback for this eventID, we need to enable
      * events on the server */
-- 
1.8.4.2