[libvirt] [PATCH 3/5] qemu_domain: Introduce qemuDomainObjBeginJobInstant

[Michal Privoznik]

The aim of this API is to allow caller do best effort. Some
functions of ours can work even when acquiring job fails (e.g.
qemuConnectGetAllDomainStats()). But what they can't bear is
delay if they have to wait up to 30 seconds for each domain.

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_domain.c | 30 +++++++++++++++++++++++++-----
 src/qemu/qemu_domain.h |  4 ++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 5273ab56ac..9657573342 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -6340,11 +6340,15 @@ qemuDomainJobAllowed(qemuDomainObjPrivatePtr priv, qemuDomainJob job)
  * @obj: domain object
  * @job: qemuDomainJob to start
  * @asyncJob: qemuDomainAsyncJob to start
+ * @instant: don't wait trying to acquire @job
  *
  * Acquires job over domain object which must be locked before
  * calling. If there's already a job running waits up to
  * QEMU_JOB_WAIT_TIME after which the functions fails reporting
- * an error.
+ * an error unless @instant is set.
+ * If @instant is true this function tries to acquire job and if
+ * it fails returns immediately without waiting. No error is
+ * reported in this case.
  *
  * Returns: 0 on success,
  *         -2 if unable to start job because of timeout or
@@ -6355,7 +6359,8 @@ static int ATTRIBUTE_NONNULL(1)
 qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
                               virDomainObjPtr obj,
                               qemuDomainJob job,
-                              qemuDomainAsyncJob asyncJob)
+                              qemuDomainAsyncJob asyncJob,
+                              bool instant)
 {
     qemuDomainObjPrivatePtr priv = obj->privateData;
     unsigned long long now;
@@ -6395,12 +6400,18 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
     }
 
     while (!nested && !qemuDomainNestedJobAllowed(priv, job)) {
+        if (instant)
+            goto cleanup;
+
         VIR_DEBUG("Waiting for async job (vm=%p name=%s)", obj, obj->def->name);
         if (virCondWaitUntil(&priv->job.asyncCond, &obj->parent.lock, then) < 0)
             goto error;
     }
 
     while (priv->job.active) {
+        if (instant)
+            goto cleanup;
+
         VIR_DEBUG("Waiting for job (vm=%p name=%s)", obj, obj->def->name);
         if (virCondWaitUntil(&priv->job.cond, &obj->parent.lock, then) < 0)
             goto error;
@@ -6517,7 +6528,7 @@ int qemuDomainObjBeginJob(virQEMUDriverPtr driver,
                           qemuDomainJob job)
 {
     if (qemuDomainObjBeginJobInternal(driver, obj, job,
-                                      QEMU_ASYNC_JOB_NONE) < 0)
+                                      QEMU_ASYNC_JOB_NONE, false) < 0)
         return -1;
     else
         return 0;
@@ -6532,7 +6543,7 @@ int qemuDomainObjBeginAsyncJob(virQEMUDriverPtr driver,
     qemuDomainObjPrivatePtr priv;
 
     if (qemuDomainObjBeginJobInternal(driver, obj, QEMU_JOB_ASYNC,
-                                      asyncJob) < 0)
+                                      asyncJob, false) < 0)
         return -1;
 
     priv = obj->privateData;
@@ -6561,9 +6572,18 @@ qemuDomainObjBeginNestedJob(virQEMUDriverPtr driver,
 
     return qemuDomainObjBeginJobInternal(driver, obj,
                                          QEMU_JOB_ASYNC_NESTED,
-                                         QEMU_ASYNC_JOB_NONE);
+                                         QEMU_ASYNC_JOB_NONE,
+                                         false);
 }
 
+int
+qemuDomainObjBeginJobInstant(virQEMUDriverPtr driver,
+                             virDomainObjPtr obj,
+                             qemuDomainJob job)
+{
+    return qemuDomainObjBeginJobInternal(driver, obj, job,
+                                         QEMU_ASYNC_JOB_NONE, true);
+}
 
 /*
  * obj must be locked and have a reference before calling
diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h
index f17157b951..4b63c00dff 100644
--- a/src/qemu/qemu_domain.h
+++ b/src/qemu/qemu_domain.h
@@ -512,6 +512,10 @@ int qemuDomainObjBeginNestedJob(virQEMUDriverPtr driver,
                                 virDomainObjPtr obj,
                                 qemuDomainAsyncJob asyncJob)
     ATTRIBUTE_RETURN_CHECK;
+int qemuDomainObjBeginJobInstant(virQEMUDriverPtr driver,
+                                 virDomainObjPtr obj,
+                                 qemuDomainJob job)
+    ATTRIBUTE_RETURN_CHECK;
 
 void qemuDomainObjEndJob(virQEMUDriverPtr driver,
                          virDomainObjPtr obj);
-- 
2.16.4