From 926144680056dd6773d9ef8ad64c4a593dd597a9 Mon Sep 17 00:00:00 2001

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Date: Wed, 25 Oct 2017 18:28:34 +0200

Subject: [PATCH 15/19] migration: Wait for semaphore before completing

 migration

RH-Author: Dr. David Alan Gilbert <dgilbert@redhat.com>

Message-id: <20171025182838.31829-4-dgilbert@redhat.com>

Patchwork-id: 77439

O-Subject: [RHV-7.5 qemu-kvm-rhev PATCH 3/7] migration: Wait for semaphore before completing migration

Bugzilla: 1497120

RH-Acked-by: Peter Xu <peterx@redhat.com>

RH-Acked-by: Juan Quintela <quintela@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

Wait for a semaphore before completing the migration,

if the previously added capability was enabled.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

Signed-off-by: Juan Quintela <quintela@redhat.com>

(cherry picked from commit e91d8951d59d483f085f7650381b8e55a1a55e4c)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 migration/migration.c | 38 ++++++++++++++++++++++++++++++++++++++

 migration/migration.h |  3 +++

 2 files changed, 41 insertions(+)

diff --git a/migration/migration.c b/migration/migration.c

index 54db29f..436e122 100644

--- a/migration/migration.c

+++ b/migration/migration.c

@@ -1847,6 +1847,39 @@ fail:

 }

 /**

+ * migration_maybe_pause: Pause if required to by

+ * migrate_pause_before_switchover called with the iothread locked

+ * Returns: 0 on success

+ */

+static int migration_maybe_pause(MigrationState *s, int *current_active_state)

+{

+    if (!migrate_pause_before_switchover()) {

+        return 0;

+    }

+

+    /* Since leaving this state is not atomic with posting the semaphore

+     * it's possible that someone could have issued multiple migrate_continue

+     * and the semaphore is incorrectly positive at this point;

+     * the docs say it's undefined to reinit a semaphore that's already

+     * init'd, so use timedwait to eat up any existing posts.

+     */

+    while (qemu_sem_timedwait(&s->pause_sem, 1) == 0) {

+        /* This block intentionally left blank */

+    }

+

+    qemu_mutex_unlock_iothread();

+    migrate_set_state(&s->state, *current_active_state,

+                      MIGRATION_STATUS_PRE_SWITCHOVER);

+    qemu_sem_wait(&s->pause_sem);

+    migrate_set_state(&s->state, MIGRATION_STATUS_PRE_SWITCHOVER,

+                      MIGRATION_STATUS_DEVICE);

+    *current_active_state = MIGRATION_STATUS_DEVICE;

+    qemu_mutex_lock_iothread();

+

+    return s->state == MIGRATION_STATUS_DEVICE ? 0 : -EINVAL;

+}

+

+/**

  * migration_completion: Used by migration_thread when there's not much left.

  *   The caller 'breaks' the loop when this returns.

  *

@@ -1872,6 +1905,9 @@ static void migration_completion(MigrationState *s, int current_active_state,

             bool inactivate = !migrate_colo_enabled();

             ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);

             if (ret >= 0) {

+                ret = migration_maybe_pause(s, &current_active_state);

+            }

+            if (ret >= 0) {

                 qemu_file_set_rate_limit(s->to_dst_file, INT64_MAX);

                 ret = qemu_savevm_state_complete_precopy(s->to_dst_file, false,

                                                          inactivate);

@@ -2239,6 +2275,7 @@ static void migration_instance_finalize(Object *obj)

     g_free(params->tls_hostname);

     g_free(params->tls_creds);

+    qemu_sem_destroy(&ms->pause_sem);

 }

 static void migration_instance_init(Object *obj)

@@ -2249,6 +2286,7 @@ static void migration_instance_init(Object *obj)

     ms->state = MIGRATION_STATUS_NONE;

     ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE;

     ms->mbps = -1;

+    qemu_sem_init(&ms->pause_sem, 0);

     params->tls_hostname = g_strdup("");

     params->tls_creds = g_strdup("");

diff --git a/migration/migration.h b/migration/migration.h

index 2eebad8..895cc34 100644

--- a/migration/migration.h

+++ b/migration/migration.h

@@ -120,6 +120,9 @@ struct MigrationState

     /* Flag set once the migration thread called bdrv_inactivate_all */

     bool block_inactive;

+    /* Migration is paused due to pause-before-switchover */

+    QemuSemaphore pause_sem;

+

     /* The semaphore is used to notify COLO thread that failover is finished */

     QemuSemaphore colo_exit_sem;

-- 

1.8.3.1