From e91d8951d59d483f085f7650381b8e55a1a55e4c Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Fri, 20 Oct 2017 10:05:52 +0100 Subject: [PATCH] migration: Wait for semaphore before completing migration Wait for a semaphore before completing the migration, if the previously added capability was enabled. Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Peter Xu Reviewed-by: Juan Quintela Signed-off-by: Juan Quintela --- migration/migration.c | 38 ++++++++++++++++++++++++++++++++++++++ migration/migration.h | 3 +++ 2 files changed, 41 insertions(+) diff --git a/migration/migration.c b/migration/migration.c index f15372e007..ef84d2c1fb 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1957,6 +1957,39 @@ fail: return -1; } +/** + * 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. @@ -1982,6 +2015,9 @@ static void migration_completion(MigrationState *s, int current_active_state, if (!ret) { bool inactivate = !migrate_colo_enabled(); ret = vm_stop_force_state(RUN_STATE_FINISH_MIGRATE); + if (ret >= 0) { + ret = migration_maybe_pause(s, ¤t_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, @@ -2363,6 +2399,7 @@ 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) @@ -2373,6 +2410,7 @@ 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 969866303e..cd988a99b9 100644 --- a/migration/migration.h +++ b/migration/migration.h @@ -121,6 +121,9 @@ 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;