lxc: completely rework reference counting

This patch follows the pattern used in qemu driver regarding
reference counting.
It changes lxcDomObjFromDomain() to ref the domain (using
virDomainObjListFindByUUIDRef()) and adds virDomainObjEndAPI() which
should be the only function in which the return value of
virObjectUnref() is checked.  This makes all reference counting
deterministic and makes the code a bit clearer.

Signed-off-by: Katerina Koukiou <k.koukiou@gmail.com>

src/lxc/lxc_domain.c

@@ -79,8 +79,8 @@ virLXCDomainObjFreeJob(virLXCDomainObjPrivatePtr priv)
  * This must be called by anything that will change the VM state
  * in any way
  *
- * Upon successful return, the object will have its ref count increased,
- * successful calls must be followed by EndJob eventually
+ * Upon successful return, the object will have its ref count increased.
+ * Successful calls must be followed by EndJob eventually.
  */
 int
 virLXCDomainObjBeginJob(virLXCDriverPtr driver ATTRIBUTE_UNUSED,
@@ -95,8 +95,6 @@ virLXCDomainObjBeginJob(virLXCDriverPtr driver ATTRIBUTE_UNUSED,
         return -1;
     then = now + LXC_JOB_WAIT_TIME;
 
-    virObjectRef(obj);
-
     while (priv->job.active) {
         VIR_DEBUG("Wait normal job condition for starting job: %s",
                   virLXCDomainJobTypeToString(job));
@@ -126,23 +124,17 @@ virLXCDomainObjBeginJob(virLXCDriverPtr driver ATTRIBUTE_UNUSED,
     else
         virReportSystemError(errno,
                              "%s", _("cannot acquire job mutex"));
-
-    virObjectUnref(obj);
     return -1;
 }
 
 
 /*
- * obj must be locked before calling
+ * obj must be locked and have a reference before calling
  *
  * To be called after completing the work associated with the
  * earlier virLXCDomainBeginJob() call
- *
- * Returns true if the remaining reference count on obj is
- * non-zero, false if the reference count has dropped to zero
- * and obj is disposed.
  */
-bool
+void
 virLXCDomainObjEndJob(virLXCDriverPtr driver ATTRIBUTE_UNUSED,
                      virDomainObjPtr obj)
 {
@@ -154,8 +146,6 @@ virLXCDomainObjEndJob(virLXCDriverPtr driver ATTRIBUTE_UNUSED,
 
     virLXCDomainObjResetJob(priv);
     virCondSignal(&priv->job.cond);
-
-    return virObjectUnref(obj);
 }
 
 

src/lxc/lxc_domain.h

@@ -102,10 +102,9 @@ virLXCDomainObjBeginJob(virLXCDriverPtr driver,
                        enum virLXCDomainJob job)
     ATTRIBUTE_RETURN_CHECK;
 
-bool
+void
 virLXCDomainObjEndJob(virLXCDriverPtr driver,
-                     virDomainObjPtr obj)
-    ATTRIBUTE_RETURN_CHECK;
+                     virDomainObjPtr obj);
 
 
 #endif /* __LXC_DOMAIN_H__ */

src/lxc/lxc_driver.c

@@ -126,11 +126,11 @@ static virNWFilterCallbackDriver lxcCallbackDriver = {
  * lxcDomObjFromDomain:
  * @domain: Domain pointer that has to be looked up
  *
- * This function looks up @domain and returns the appropriate
- * virDomainObjPtr.
+ * This function looks up @domain and returns the appropriate virDomainObjPtr
+ * that has to be released by calling virDomainObjEndAPI.
  *
- * Returns the domain object which is locked on success, NULL
- * otherwise.
+ * Returns the domain object with incremented reference counter which is locked
+ * on success, NULL otherwise.
  */
 static virDomainObjPtr
 lxcDomObjFromDomain(virDomainPtr domain)
@@ -139,7 +139,7 @@ lxcDomObjFromDomain(virDomainPtr domain)
     virLXCDriverPtr driver = domain->conn->privateData;
     char uuidstr[VIR_UUID_STRING_BUFLEN];
 
-    vm = virDomainObjListFindByUUID(driver->domains, domain->uuid);
+    vm = virDomainObjListFindByUUIDRef(driver->domains, domain->uuid);
     if (!vm) {
         virUUIDFormat(domain->uuid, uuidstr);
         virReportError(VIR_ERR_NO_DOMAIN,
@@ -283,7 +283,7 @@ static virDomainPtr lxcDomainLookupByUUID(virConnectPtr conn,
     virDomainObjPtr vm;
     virDomainPtr dom = NULL;
 
-    vm = virDomainObjListFindByUUID(driver->domains, uuid);
+    vm = virDomainObjListFindByUUIDRef(driver->domains, uuid);
 
     if (!vm) {
         char uuidstr[VIR_UUID_STRING_BUFLEN];
@@ -301,8 +301,7 @@ static virDomainPtr lxcDomainLookupByUUID(virConnectPtr conn,
         dom->id = vm->def->id;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return dom;
 }
 
@@ -347,8 +346,7 @@ static int lxcDomainIsActive(virDomainPtr dom)
     ret = virDomainObjIsActive(obj);
 
  cleanup:
-    if (obj)
-        virObjectUnlock(obj);
+    virDomainObjEndAPI(&obj);
     return ret;
 }
 
@@ -367,8 +365,7 @@ static int lxcDomainIsPersistent(virDomainPtr dom)
     ret = obj->persistent;
 
  cleanup:
-    if (obj)
-        virObjectUnlock(obj);
+    virDomainObjEndAPI(&obj);
     return ret;
 }
 
@@ -386,8 +383,7 @@ static int lxcDomainIsUpdated(virDomainPtr dom)
     ret = obj->updated;
 
  cleanup:
-    if (obj)
-        virObjectUnlock(obj);
+    virDomainObjEndAPI(&obj);
     return ret;
 }
 
@@ -492,13 +488,14 @@ lxcDomainDefineXMLFlags(virConnectPtr conn, const char *xml, unsigned int flags)
                                    driver->xmlopt,
                                    0, &oldDef)))
         goto cleanup;
+
+    virObjectRef(vm);
     def = NULL;
     vm->persistent = 1;
 
     if (virDomainSaveConfig(cfg->configDir, driver->caps,
                             vm->newDef ? vm->newDef : vm->def) < 0) {
         virDomainObjListRemove(driver->domains, vm);
-        vm = NULL;
         goto cleanup;
     }
 
@@ -515,8 +512,7 @@ lxcDomainDefineXMLFlags(virConnectPtr conn, const char *xml, unsigned int flags)
  cleanup:
     virDomainDefFree(def);
     virDomainDefFree(oldDef);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(caps);
@@ -566,14 +562,12 @@ static int lxcDomainUndefineFlags(virDomainPtr dom,
         vm->persistent = 0;
     } else {
         virDomainObjListRemove(driver->domains, vm);
-        vm = NULL;
     }
 
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(cfg);
@@ -628,8 +622,7 @@ static int lxcDomainGetInfo(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -654,8 +647,7 @@ lxcDomainGetState(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -674,8 +666,7 @@ static char *lxcDomainGetOSType(virDomainPtr dom)
         goto cleanup;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -695,8 +686,7 @@ lxcDomainGetMaxMemory(virDomainPtr dom)
     ret = virDomainDefGetMemoryActual(vm->def);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -790,12 +780,10 @@ static int lxcDomainSetMemoryFlags(virDomainPtr dom, unsigned long newmem,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -940,12 +928,10 @@ lxcDomainSetMemoryParameters(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -1042,8 +1028,7 @@ lxcDomainGetMemoryParameters(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     return ret;
 }
@@ -1069,8 +1054,7 @@ static char *lxcDomainGetXMLDesc(virDomainPtr dom,
                              virDomainDefFormatConvertXMLFlags(flags));
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -1166,12 +1150,10 @@ static int lxcDomainCreateWithFiles(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(cfg);
@@ -1301,13 +1283,11 @@ lxcDomainCreateXMLWithFiles(virConnectPtr conn,
         dom->id = vm->def->id;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
     virDomainDefFree(def);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
     virObjectUnref(caps);
@@ -1390,8 +1370,7 @@ static int lxcDomainGetSecurityLabel(virDomainPtr dom, virSecurityLabelPtr secla
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -1568,12 +1547,10 @@ lxcDomainDestroyFlags(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
     return ret;
@@ -1907,8 +1884,7 @@ static char *lxcDomainGetSchedulerType(virDomainPtr dom,
     ignore_value(VIR_STRDUP(ret, "posix"));
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -2089,13 +2065,11 @@ lxcDomainSetSchedulerParametersFlags(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
     virDomainDefFree(vmdef);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -2206,8 +2180,7 @@ lxcDomainGetSchedulerParametersFlags(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     return ret;
 }
@@ -2461,12 +2434,10 @@ lxcDomainBlockStats(virDomainPtr dom,
                                             &stats->wr_req);
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -2594,12 +2565,10 @@ lxcDomainBlockStatsFlags(virDomainPtr dom,
     *nparams = tmp;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -2809,12 +2778,10 @@ lxcDomainSetBlkioParameters(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -3209,8 +3176,7 @@ lxcDomainGetBlkioParameters(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     return ret;
 }
@@ -3258,12 +3224,10 @@ lxcDomainInterfaceStats(virDomainPtr dom,
                        _("Invalid path, '%s' is not a known interface"), path);
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 #else
@@ -3293,8 +3257,7 @@ static int lxcDomainGetAutostart(virDomainPtr dom,
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -3365,13 +3328,12 @@ static int lxcDomainSetAutostart(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     VIR_FREE(configFile);
     VIR_FREE(autostartLink);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(cfg);
     return ret;
 }
@@ -3503,13 +3465,12 @@ static int lxcDomainSuspend(virDomainPtr dom)
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(cfg);
     return ret;
 }
@@ -3559,13 +3520,12 @@ static int lxcDomainResume(virDomainPtr dom)
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     if (event)
         virObjectEventStateQueue(driver->domainEventState, event);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(cfg);
     return ret;
 }
@@ -3630,8 +3590,7 @@ lxcDomainOpenConsole(virDomainPtr dom,
 
     ret = 0;
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -3707,12 +3666,10 @@ lxcDomainSendProcessSignal(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -3814,12 +3771,10 @@ lxcDomainShutdownFlags(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -3899,12 +3854,10 @@ lxcDomainReboot(virDomainPtr dom,
     ret = 0;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -5208,15 +5161,14 @@ static int lxcDomainAttachDeviceFlags(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     virDomainDefFree(vmdef);
     if (dev != dev_copy)
         virDomainDeviceDefFree(dev_copy);
     virDomainDeviceDefFree(dev);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -5314,15 +5266,14 @@ static int lxcDomainUpdateDeviceFlags(virDomainPtr dom,
         }
     }
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     virDomainDefFree(vmdef);
     if (dev != dev_copy)
         virDomainDeviceDefFree(dev_copy);
     virDomainDeviceDefFree(dev);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -5419,15 +5370,14 @@ static int lxcDomainDetachDeviceFlags(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
     virDomainDefFree(vmdef);
     if (dev != dev_copy)
         virDomainDeviceDefFree(dev_copy);
     virDomainDeviceDefFree(dev);
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -5484,12 +5434,10 @@ static int lxcDomainLxcOpenNamespace(virDomainPtr dom,
     ret = nfds;
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -5586,11 +5534,10 @@ lxcDomainMemoryStats(virDomainPtr dom,
     }
 
  endjob:
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
+
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -5738,12 +5685,10 @@ lxcDomainSetMetadata(virDomainPtr dom,
                                   driver->xmlopt, cfg->stateDir,
                                   cfg->configDir, flags);
 
-    if (!virLXCDomainObjEndJob(driver, vm))
-        vm = NULL;
+    virLXCDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     virObjectUnref(cfg);
     return ret;
@@ -5773,7 +5718,7 @@ lxcDomainGetMetadata(virDomainPtr dom,
     ret = virDomainObjGetMetadata(vm, type, uri, caps, driver->xmlopt, flags);
 
  cleanup:
-    virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     virObjectUnref(caps);
     return ret;
 }
@@ -5820,7 +5765,7 @@ lxcDomainGetCPUStats(virDomainPtr dom,
         ret = virCgroupGetPercpuStats(priv->cgroup, params,
                                       nparams, start_cpu, ncpus, NULL);
  cleanup:
-    virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }
 
@@ -5881,8 +5826,7 @@ lxcDomainHasManagedSaveImage(virDomainPtr dom, unsigned int flags)
     ret = 0;
 
  cleanup:
-    if (vm)
-        virObjectUnlock(vm);
+    virDomainObjEndAPI(&vm);
     return ret;
 }