qemu: Introduce APIs for manipulating qemuDomainAgentJob

The point is to break QEMU_JOB_* into smaller pieces which
enables us to achieve higher throughput. For instance, if there
are two threads, one is trying to query something on qemu
monitor while the other is trying to query something on agent
monitor these two threads would serialize. There is not much
reason for that.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJiri Denemark <jdenemar@redhat.com>

src/qemu/THREADS.txt

@@ -51,8 +51,8 @@ There are a number of locks on various objects
     Since virDomainObjPtr lock must not be held during sleeps, the job
     conditions provide additional protection for code making updates.
 
-    QEMU driver uses two kinds of job conditions: asynchronous and
-    normal.
+    QEMU driver uses three kinds of job conditions: asynchronous, agent
+    and normal.
 
     Asynchronous job condition is used for long running jobs (such as
     migration) that consist of several monitor commands and it is
@@ -69,16 +69,23 @@ There are a number of locks on various objects
     it needs to wait until the asynchronous job ends and try to acquire
     the job again.
 
+    Agent job condition is then used when thread wishes to talk to qemu
+    agent monitor. It is possible to acquire just agent job
+    (qemuDomainObjBeginAgentJob), or only normal job
+    (qemuDomainObjBeginJob) or both at the same time
+    (qemuDomainObjBeginJobWithAgent). Which type of job to grab depends
+    whether caller wishes to communicate only with agent socket, or only
+    with qemu monitor socket or both, respectively.
+
     Immediately after acquiring the virDomainObjPtr lock, any method
-    which intends to update state must acquire either asynchronous or
-    normal job condition.  The virDomainObjPtr lock is released while
-    blocking on these condition variables.  Once the job condition is
-    acquired, a method can safely release the virDomainObjPtr lock
-    whenever it hits a piece of code which may sleep/wait, and
-    re-acquire it after the sleep/wait.  Whenever an asynchronous job
-    wants to talk to the monitor, it needs to acquire nested job (a
-    special kind of normal job) to obtain exclusive access to the
-    monitor.
+    which intends to update state must acquire asynchronous, normal or
+    agent job . The virDomainObjPtr lock is released while blocking on
+    these condition variables.  Once the job condition is acquired, a
+    method can safely release the virDomainObjPtr lock whenever it hits
+    a piece of code which may sleep/wait, and re-acquire it after the
+    sleep/wait.  Whenever an asynchronous job wants to talk to the
+    monitor, it needs to acquire nested job (a special kind of normal
+    job) to obtain exclusive access to the monitor.
 
     Since the virDomainObjPtr lock was dropped while waiting for the
     job condition, it is possible that the domain is no longer active
@@ -132,6 +139,30 @@ To acquire the normal job condition
 
 
 
+To acquire the agent job condition
+
+  qemuDomainObjBeginAgentJob()
+    - Waits until there is no other agent job set
+    - Sets job.agentActive tp the job type
+
+  qemuDomainObjEndAgentJob()
+    - Sets job.agentActive to 0
+    - Signals on job.cond condition
+
+
+
+To acquire both normal and agent job condition
+
+  qemuDomainObjBeginJobWithAgent()
+    - Waits until there is no normal and no agent job set
+    - Sets both job.active and job.agentActive with required job types
+
+  qemuDomainObjEndJobWithAgent()
+    - Sets both job.active and job.agentActive to 0
+    - Signals on job.cond condition
+
+
+
 To acquire the asynchronous job condition
 
   qemuDomainObjBeginAsyncJob()
@@ -247,6 +278,65 @@ Design patterns
      virDomainObjEndAPI(&obj);
 
 
+ * Invoking an agent command on a virDomainObjPtr
+
+     virDomainObjPtr obj;
+     qemuAgentPtr agent;
+
+     obj = qemuDomObjFromDomain(dom);
+
+     qemuDomainObjBeginAgentJob(obj, QEMU_AGENT_JOB_TYPE);
+
+     ...do prep work...
+
+     if (!qemuDomainAgentAvailable(obj, true))
+         goto cleanup;
+
+     agent = qemuDomainObjEnterAgent(obj);
+     qemuAgentXXXX(agent, ..);
+     qemuDomainObjExitAgent(obj, agent);
+
+     ...do final work...
+
+     qemuDomainObjEndAgentJob(obj);
+     virDomainObjEndAPI(&obj);
+
+
+ * Invoking both monitor and agent commands on a virDomainObjPtr
+
+     virDomainObjPtr obj;
+     qemuAgentPtr agent;
+
+     obj = qemuDomObjFromDomain(dom);
+
+     qemuDomainObjBeginJobWithAgent(obj, QEMU_JOB_TYPE, QEMU_AGENT_JOB_TYPE);
+
+     if (!virDomainObjIsActive(dom))
+         goto cleanup;
+
+     ...do prep work...
+
+     if (!qemuDomainAgentAvailable(obj, true))
+         goto cleanup;
+
+     agent = qemuDomainObjEnterAgent(obj);
+     qemuAgentXXXX(agent, ..);
+     qemuDomainObjExitAgent(obj, agent);
+
+     ...
+
+     qemuDomainObjEnterMonitor(obj);
+     qemuMonitorXXXX(priv->mon);
+     qemuDomainObjExitMonitor(obj);
+
+     /* Alternatively, talk to the monitor first and then talk to the agent. */
+
+     ...do final work...
+
+     qemuDomainObjEndJobWithAgent(obj);
+     virDomainObjEndAPI(&obj);
+
+
  * Running asynchronous job
 
      virDomainObjPtr obj;

src/qemu/qemu_domain.c

@@ -313,6 +313,19 @@ qemuDomainObjResetJob(qemuDomainObjPrivatePtr priv)
     job->started = 0;
 }
 
+
+static void
+qemuDomainObjResetAgentJob(qemuDomainObjPrivatePtr priv)
+{
+    qemuDomainJobObjPtr job = &priv->job;
+
+    job->agentActive = QEMU_AGENT_JOB_NONE;
+    job->agentOwner = 0;
+    job->agentOwnerAPI = NULL;
+    job->agentStarted = 0;
+}
+
+
 static void
 qemuDomainObjResetAsyncJob(qemuDomainObjPrivatePtr priv)
 {
@@ -6356,6 +6369,17 @@ qemuDomainJobAllowed(qemuDomainObjPrivatePtr priv, qemuDomainJob job)
     return !priv->job.active && qemuDomainNestedJobAllowed(priv, job);
 }
 
+static bool
+qemuDomainObjCanSetJob(qemuDomainObjPrivatePtr priv,
+                       qemuDomainJob job,
+                       qemuDomainAgentJob agentJob)
+{
+    return ((job == QEMU_JOB_NONE ||
+             priv->job.active == QEMU_JOB_NONE) &&
+            (agentJob == QEMU_AGENT_JOB_NONE ||
+             priv->job.agentActive == QEMU_AGENT_JOB_NONE));
+}
+
 /* Give up waiting for mutex after 30 seconds */
 #define QEMU_JOB_WAIT_TIME (1000ull * 30)
 
@@ -6385,6 +6409,7 @@ static int ATTRIBUTE_NONNULL(1)
 qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
                               virDomainObjPtr obj,
                               qemuDomainJob job,
+                              qemuDomainAgentJob agentJob,
                               qemuDomainAsyncJob asyncJob,
                               bool nowait)
 {
@@ -6398,16 +6423,15 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
     int ret = -1;
     unsigned long long duration = 0;
     unsigned long long asyncDuration = 0;
-    const char *jobStr;
-
-    if (async)
-        jobStr = qemuDomainAsyncJobTypeToString(asyncJob);
-    else
-        jobStr = qemuDomainJobTypeToString(job);
 
-    VIR_DEBUG("Starting %s: %s (vm=%p name=%s, current job=%s async=%s)",
-              async ? "async job" : "job", jobStr, obj, obj->def->name,
+    VIR_DEBUG("Starting job: job=%s agentJob=%s asyncJob=%s "
+              "(vm=%p name=%s, current job=%s agentJob=%s async=%s)",
+              qemuDomainJobTypeToString(job),
+              qemuDomainAgentJobTypeToString(agentJob),
+              qemuDomainAsyncJobTypeToString(asyncJob),
+              obj, obj->def->name,
               qemuDomainJobTypeToString(priv->job.active),
+              qemuDomainAgentJobTypeToString(priv->job.agentActive),
               qemuDomainAsyncJobTypeToString(priv->job.asyncJob));
 
     if (virTimeMillisNow(&now) < 0) {
@@ -6434,7 +6458,7 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
             goto error;
     }
 
-    while (priv->job.active) {
+    while (!qemuDomainObjCanSetJob(priv, job, agentJob)) {
         if (nowait)
             goto cleanup;
 
@@ -6448,10 +6472,11 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
     if (!nested && !qemuDomainNestedJobAllowed(priv, job))
         goto retry;
 
-    qemuDomainObjResetJob(priv);
-
     ignore_value(virTimeMillisNow(&now));
 
+    if (job) {
+        qemuDomainObjResetJob(priv);
+
         if (job != QEMU_JOB_ASYNC) {
             VIR_DEBUG("Started job: %s (async=%s vm=%p name=%s)",
                       qemuDomainJobTypeToString(job),
@@ -6475,6 +6500,21 @@ qemuDomainObjBeginJobInternal(virQEMUDriverPtr driver,
             priv->job.asyncStarted = now;
             priv->job.current->started = now;
         }
+    }
+
+    if (agentJob) {
+        qemuDomainObjResetAgentJob(priv);
+
+        VIR_DEBUG("Started agent job: %s (vm=%p name=%s job=%s async=%s)",
+                  qemuDomainAgentJobTypeToString(agentJob),
+                  obj, obj->def->name,
+                  qemuDomainJobTypeToString(priv->job.active),
+                  qemuDomainAsyncJobTypeToString(priv->job.asyncJob));
+        priv->job.agentActive = agentJob;
+        priv->job.agentOwner = virThreadSelfID();
+        priv->job.agentOwnerAPI = virThreadJobGet();
+        priv->job.agentStarted = now;
+    }
 
     if (qemuDomainTrackJob(job))
         qemuDomainObjSaveJob(driver, obj);
@@ -6554,12 +6594,50 @@ int qemuDomainObjBeginJob(virQEMUDriverPtr driver,
                           qemuDomainJob job)
 {
     if (qemuDomainObjBeginJobInternal(driver, obj, job,
+                                      QEMU_AGENT_JOB_NONE,
                                       QEMU_ASYNC_JOB_NONE, false) < 0)
         return -1;
     else
         return 0;
 }
 
+/**
+ * qemuDomainObjBeginAgentJob:
+ *
+ * Grabs agent type of job. Use if caller talks to guest agent only.
+ *
+ * To end job call qemuDomainObjEndAgentJob.
+ */
+int
+qemuDomainObjBeginAgentJob(virQEMUDriverPtr driver,
+                           virDomainObjPtr obj,
+                           qemuDomainAgentJob agentJob)
+{
+    return qemuDomainObjBeginJobInternal(driver, obj, QEMU_JOB_NONE,
+                                         agentJob,
+                                         QEMU_ASYNC_JOB_NONE, false);
+}
+
+/**
+ * qemuDomainObjBeginJobWithAgent:
+ *
+ * Grabs both monitor and agent types of job. Use if caller talks to
+ * both monitor and guest agent. However, if @job (or @agentJob) is
+ * QEMU_JOB_NONE (or QEMU_AGENT_JOB_NONE) only agent job is acquired (or
+ * monitor job).
+ *
+ * To end job call qemuDomainObjEndJobWithAgent.
+ */
+int
+qemuDomainObjBeginJobWithAgent(virQEMUDriverPtr driver,
+                               virDomainObjPtr obj,
+                               qemuDomainJob job,
+                               qemuDomainAgentJob agentJob)
+{
+    return qemuDomainObjBeginJobInternal(driver, obj, job, agentJob,
+                                         QEMU_ASYNC_JOB_NONE, false);
+}
+
 int qemuDomainObjBeginAsyncJob(virQEMUDriverPtr driver,
                                virDomainObjPtr obj,
                                qemuDomainAsyncJob asyncJob,
@@ -6569,6 +6647,7 @@ int qemuDomainObjBeginAsyncJob(virQEMUDriverPtr driver,
     qemuDomainObjPrivatePtr priv;
 
     if (qemuDomainObjBeginJobInternal(driver, obj, QEMU_JOB_ASYNC,
+                                      QEMU_AGENT_JOB_NONE,
                                       asyncJob, false) < 0)
         return -1;
 
@@ -6598,6 +6677,7 @@ qemuDomainObjBeginNestedJob(virQEMUDriverPtr driver,
 
     return qemuDomainObjBeginJobInternal(driver, obj,
                                          QEMU_JOB_ASYNC_NESTED,
+                                         QEMU_AGENT_JOB_NONE,
                                          QEMU_ASYNC_JOB_NONE,
                                          false);
 }
@@ -6621,6 +6701,7 @@ qemuDomainObjBeginJobNowait(virQEMUDriverPtr driver,
                             qemuDomainJob job)
 {
     return qemuDomainObjBeginJobInternal(driver, obj, job,
+                                         QEMU_AGENT_JOB_NONE,
                                          QEMU_ASYNC_JOB_NONE, true);
 }
 
@@ -6646,7 +6727,53 @@ qemuDomainObjEndJob(virQEMUDriverPtr driver, virDomainObjPtr obj)
     qemuDomainObjResetJob(priv);
     if (qemuDomainTrackJob(job))
         qemuDomainObjSaveJob(driver, obj);
-    virCondSignal(&priv->job.cond);
+    /* We indeed need to wake up ALL threads waiting because
+     * grabbing a job requires checking more variables. */
+    virCondBroadcast(&priv->job.cond);
+}
+
+void
+qemuDomainObjEndAgentJob(virDomainObjPtr obj)
+{
+    qemuDomainObjPrivatePtr priv = obj->privateData;
+    qemuDomainAgentJob agentJob = priv->job.agentActive;
+
+    priv->jobs_queued--;
+
+    VIR_DEBUG("Stopping agent job: %s (async=%s vm=%p name=%s)",
+              qemuDomainAgentJobTypeToString(agentJob),
+              qemuDomainAsyncJobTypeToString(priv->job.asyncJob),
+              obj, obj->def->name);
+
+    qemuDomainObjResetAgentJob(priv);
+    /* We indeed need to wake up ALL threads waiting because
+     * grabbing a job requires checking more variables. */
+    virCondBroadcast(&priv->job.cond);
+}
+
+void
+qemuDomainObjEndJobWithAgent(virQEMUDriverPtr driver,
+                             virDomainObjPtr obj)
+{
+    qemuDomainObjPrivatePtr priv = obj->privateData;
+    qemuDomainJob job = priv->job.active;
+    qemuDomainAgentJob agentJob = priv->job.agentActive;
+
+    priv->jobs_queued--;
+
+    VIR_DEBUG("Stopping both jobs: %s %s (async=%s vm=%p name=%s)",
+              qemuDomainJobTypeToString(job),
+              qemuDomainAgentJobTypeToString(agentJob),
+              qemuDomainAsyncJobTypeToString(priv->job.asyncJob),
+              obj, obj->def->name);
+
+    qemuDomainObjResetJob(priv);
+    qemuDomainObjResetAgentJob(priv);
+    if (qemuDomainTrackJob(job))
+        qemuDomainObjSaveJob(driver, obj);
+    /* We indeed need to wake up ALL threads waiting because
+     * grabbing a job requires checking more variables. */
+    virCondBroadcast(&priv->job.cond);
 }
 
 void
@@ -6682,8 +6809,9 @@ qemuDomainObjAbortAsyncJob(virDomainObjPtr obj)
  * obj must be locked before calling
  *
  * To be called immediately before any QEMU monitor API call
- * Must have already either called qemuDomainObjBeginJob() and checked
- * that the VM is still active; may not be used for nested async jobs.
+ * Must have already either called qemuDomainObjBeginJob() or
+ * qemuDomainObjBeginJobWithAgent() and checked that the VM is
+ * still active; may not be used for nested async jobs.
  *
  * To be followed with qemuDomainObjExitMonitor() once complete
  */
@@ -6800,8 +6928,9 @@ qemuDomainObjEnterMonitorAsync(virQEMUDriverPtr driver,
  * obj must be locked before calling
  *
  * To be called immediately before any QEMU agent API call.
- * Must have already called qemuDomainObjBeginJob() and checked
- * that the VM is still active.
+ * Must have already called qemuDomainObjBeginAgentJob() or
+ * qemuDomainObjBeginJobWithAgent() and checked that the VM is
+ * still active.
  *
  * To be followed with qemuDomainObjExitAgent() once complete
  */

src/qemu/qemu_domain.h

@@ -518,6 +518,15 @@ int qemuDomainObjBeginJob(virQEMUDriverPtr driver,
                           virDomainObjPtr obj,
                           qemuDomainJob job)
     ATTRIBUTE_RETURN_CHECK;
+int qemuDomainObjBeginAgentJob(virQEMUDriverPtr driver,
+                               virDomainObjPtr obj,
+                               qemuDomainAgentJob agentJob)
+    ATTRIBUTE_RETURN_CHECK;
+int qemuDomainObjBeginJobWithAgent(virQEMUDriverPtr driver,
+                                   virDomainObjPtr obj,
+                                   qemuDomainJob job,
+                                   qemuDomainAgentJob agentJob)
+    ATTRIBUTE_RETURN_CHECK;
 int qemuDomainObjBeginAsyncJob(virQEMUDriverPtr driver,
                                virDomainObjPtr obj,
                                qemuDomainAsyncJob asyncJob,
@@ -535,6 +544,9 @@ int qemuDomainObjBeginJobNowait(virQEMUDriverPtr driver,
 
 void qemuDomainObjEndJob(virQEMUDriverPtr driver,
                          virDomainObjPtr obj);
+void qemuDomainObjEndAgentJob(virDomainObjPtr obj);
+void qemuDomainObjEndJobWithAgent(virQEMUDriverPtr driver,
+                                  virDomainObjPtr obj);
 void qemuDomainObjEndAsyncJob(virQEMUDriverPtr driver,
                               virDomainObjPtr obj);
 void qemuDomainObjAbortAsyncJob(virDomainObjPtr obj);