File b9a5faea-libxl-handle-death-thread.patch of Package libvirt.29527

commit b9a5faea49b7412e26d7389af4c32fc2b3ee80e5
Author: Jim Fehlig <jfehlig@suse.com>
Date:   Wed Nov 24 11:36:55 2021 -0700

    libxl: Handle domain death events in a thread
    
    Similar to domain shutdown events, processing domain death events can be a
    lengthy process and we don't want to block the event handler while the
    operation completes. Move the death handling function to a thread.
    
    Signed-off-by: Jim Fehlig <jfehlig@suse.com>
    Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
    Reviewed-by: Ján Tomko <jtomko@redhat.com>

Index: libvirt-6.0.0/src/libxl/libxl_domain.c
===================================================================
--- libvirt-6.0.0.orig/src/libxl/libxl_domain.c
+++ libvirt-6.0.0/src/libxl/libxl_domain.c
@@ -604,12 +604,17 @@ libxlDomainShutdownThread(void *opaque)
 }
 
 static void
-libxlDomainHandleDeath(libxlDriverPrivatePtr driver, virDomainObjPtr vm)
+libxlDomainDeathThread(void *opaque)
 {
+    struct libxlEventHandlerThreadInfo *death_info = opaque;
+    virDomainObjPtr vm = death_info->vm;
+    libxl_event *ev = death_info->event;
+    libxlDriverPrivatePtr driver = death_info->driver;
     virObjectEventPtr dom_event = NULL;
+    g_autoptr(libxlDriverConfig) cfg = libxlDriverConfigGet(driver);
 
     if (libxlDomainObjBeginJob(driver, vm, LIBXL_JOB_MODIFY) < 0)
-        return;
+        goto cleanup;
 
     virDomainObjSetState(vm, VIR_DOMAIN_SHUTOFF, VIR_DOMAIN_SHUTOFF_DESTROYED);
     dom_event = virDomainEventLifecycleNewFromObj(vm,
@@ -620,6 +625,11 @@ libxlDomainHandleDeath(libxlDriverPrivat
         virDomainObjListRemove(driver->domains, vm);
     libxlDomainObjEndJob(driver, vm);
     virObjectEventStateQueue(driver->domainEventState, dom_event);
+
+ cleanup:
+    virDomainObjEndAPI(&vm);
+    libxl_event_free(cfg->ctx, ev);
+    VIR_FREE(death_info);
 }
 
 
@@ -633,6 +643,8 @@ libxlDomainEventHandler(void *data, VIR_
     libxl_shutdown_reason xl_reason = event->u.domain_shutdown.shutdown_reason;
     virDomainObjPtr vm = NULL;
     g_autoptr(libxlDriverConfig) cfg = NULL;
+    struct libxlEventHandlerThreadInfo *thread_info = NULL;
+    virThread thread;
 
     VIR_DEBUG("Received libxl event '%d' for domid '%d'", event->type, event->domid);
 
@@ -655,30 +667,27 @@ libxlDomainEventHandler(void *data, VIR_
         goto cleanup;
     }
 
+    /*
+     * Start event-specific threads to handle shutdown and death.
+     * They are potentially lengthy operations and we don't want to be
+     * blocking this event handler while they are in progress.
+     */
     if (event->type == LIBXL_EVENT_TYPE_DOMAIN_SHUTDOWN) {
-        struct libxlEventHandlerThreadInfo *shutdown_info = NULL;
-        virThread thread;
-
-        /*
-         * Start a thread to handle shutdown.  We don't want to be tying up
-         * libxl's event machinery by doing a potentially lengthy shutdown.
-         */
-        if (VIR_ALLOC(shutdown_info) < 0)
+        if (VIR_ALLOC(thread_info) < 0)
             goto cleanup;
 
-        shutdown_info->driver = driver;
-        shutdown_info->vm = vm;
-        shutdown_info->event = (libxl_event *)event;
+        thread_info->driver = driver;
+        thread_info->vm = vm;
+        thread_info->event = (libxl_event *)event;
         /*
          * Cleanup will be handled by the shutdown thread.
          */
         if (virThreadCreate(&thread, false, libxlDomainShutdownThread,
-                            shutdown_info) < 0) {
+                            thread_info) < 0) {
             /*
              * Not much we can do on error here except log it.
              */
             VIR_ERROR(_("Failed to create thread to handle domain shutdown"));
-            VIR_FREE(shutdown_info);
             goto cleanup;
         }
         /*
@@ -687,15 +696,34 @@ libxlDomainEventHandler(void *data, VIR_
          */
         return;
     } else if (event->type == LIBXL_EVENT_TYPE_DOMAIN_DEATH) {
+        if (VIR_ALLOC(thread_info) < 0)
+            goto cleanup;
+
+        thread_info->driver = driver;
+        thread_info->vm = vm;
+        thread_info->event = (libxl_event *)event;
         /*
-         * On death the domain is cleaned up from Xen's perspective.
-         * Cleanup on the libvirt side can be done synchronously.
+         * Cleanup will be handled by the shutdown thread.
          */
-        libxlDomainHandleDeath(driver, vm);
+        if (virThreadCreate(&thread, false, libxlDomainDeathThread,
+                            thread_info) < 0) {
+            /*
+             * Not much we can do on error here except log it.
+             */
+            VIR_ERROR(_("Failed to create thread to handle domain death"));
+            goto cleanup;
+        }
+        /*
+         * virDomainObjEndAPI is called in the death thread, where
+         * libxlEventHandlerThreadInfo and libxl_event are also freed.
+         */
+        return;
+
     }
 
  cleanup:
     virDomainObjEndAPI(&vm);
+    VIR_FREE(thread_info);
     cfg = libxlDriverConfigGet(driver);
     /* Cast away any const */
     libxl_event_free(cfg->ctx, (libxl_event *)event);