The QMP command query_migrate might see incorrect throughput numbers if it runs after we've set the migration completion status but before migration_calculate_complete() has updated s->total_time and s->mbps.
The migration status would show COMPLETED, but the throughput value would be the one from the last iteration and not the one from the whole migration. This will usually be a larger value due to the time period being smaller (one iteration). Move migration_calculate_complete() earlier so that the status MIGRATION_STATUS_COMPLETED is only emitted after the final counters update. Keep everything under the BQL so the QMP thread sees the updates as atomic. Rename migration_calculate_complete to migration_completion_end to reflect its new purpose of also updating s->state. Signed-off-by: Fabiano Rosas <faro...@suse.de> --- v2: - improved comments; - took the suggestion of creating a new function but used 'end' instead of 'finalize' to avoid possible confusion with QOM. CI run: https://gitlab.com/farosas/qemu/-/pipelines/1191024660 --- migration/migration.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index ab21de2cad..7b0e528d01 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -102,6 +102,7 @@ static int migration_maybe_pause(MigrationState *s, int new_state); static void migrate_fd_cancel(MigrationState *s); static bool close_return_path_on_source(MigrationState *s); +static void migration_completion_end(MigrationState *s); static void migration_downtime_start(MigrationState *s) { @@ -2746,8 +2747,7 @@ static void migration_completion(MigrationState *s) migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE, MIGRATION_STATUS_COLO); } else { - migrate_set_state(&s->state, current_active_state, - MIGRATION_STATUS_COMPLETED); + migration_completion_end(s); } return; @@ -2784,8 +2784,7 @@ static void bg_migration_completion(MigrationState *s) goto fail; } - migrate_set_state(&s->state, current_active_state, - MIGRATION_STATUS_COMPLETED); + migration_completion_end(s); return; fail: @@ -2987,18 +2986,28 @@ static MigThrError migration_detect_error(MigrationState *s) } } -static void migration_calculate_complete(MigrationState *s) +static void migration_completion_end(MigrationState *s) { uint64_t bytes = migration_transferred_bytes(); int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); int64_t transfer_time; + /* + * Take the BQL here so that query-migrate on the QMP thread sees: + * - atomic update of s->total_time and s->mbps; + * - correct ordering of s->mbps update vs. s->state; + */ + bql_lock(); migration_downtime_end(s); s->total_time = end_time - s->start_time; transfer_time = s->total_time - s->setup_time; if (transfer_time) { s->mbps = ((double) bytes * 8.0) / transfer_time / 1000; } + + migrate_set_state(&s->state, s->state, + MIGRATION_STATUS_COMPLETED); + bql_unlock(); } static void update_iteration_initial_status(MigrationState *s) @@ -3145,7 +3154,6 @@ static void migration_iteration_finish(MigrationState *s) bql_lock(); switch (s->state) { case MIGRATION_STATUS_COMPLETED: - migration_calculate_complete(s); runstate_set(RUN_STATE_POSTMIGRATE); break; case MIGRATION_STATUS_COLO: @@ -3189,9 +3197,6 @@ static void bg_migration_iteration_finish(MigrationState *s) bql_lock(); switch (s->state) { case MIGRATION_STATUS_COMPLETED: - migration_calculate_complete(s); - break; - case MIGRATION_STATUS_ACTIVE: case MIGRATION_STATUS_FAILED: case MIGRATION_STATUS_CANCELLED: -- 2.35.3
