Cédric Le Goater <[email protected]> writes: > Hello Fabiano > > On 2/8/24 14:29, Fabiano Rosas wrote: >> Cédric Le Goater <[email protected]> writes: >> >>> In case of error, close_return_path_on_source() can perform a shutdown >>> to exit the return-path thread. However, in migrate_fd_cleanup(), >>> 'to_dst_file' is closed before calling close_return_path_on_source() >>> and the shutdown fails, leaving the source and destination waiting for >>> an event to occur. >> >> Hi, Cédric >> >> Are you sure this is not caused by patch 13? > > It happens with upstream QEMU without any patch.
I might have taken that "shutdown fails" in the commit message too literaly. Anyway, I have a proposed solution: -->8-- >From 729aa7b5b7f130f756d41649fdd0862bd2e90430 Mon Sep 17 00:00:00 2001 From: Fabiano Rosas <[email protected]> Date: Wed, 14 Feb 2024 16:45:43 -0300 Subject: [PATCH] migration: Join the return path thread before releasing to_dst_file MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The return path thread might hang at a blocking system call. Before joining the thread we might need to issue a shutdown() on the socket file descriptor to release it. To determine whether the shutdown() is necessary we look at the QEMUFile error. Make sure we only clean up the QEMUFile after the return path has been waited for. This fixes a hang when qemu_savevm_state_setup() produced an error that was detected by migration_detect_error(). That skips migration_completion() so close_return_path_on_source() would get stuck waiting for the RP thread to terminate. At migrate_fd_cleanup() I'm keeping the relative order of joining the migration thread and the return path just in case. Reported-by: Cédric Le Goater <[email protected]> Signed-off-by: Fabiano Rosas <[email protected]> --- migration/migration.c | 36 ++++++++++++++++-------------------- 1 file changed, 16 insertions(+), 20 deletions(-) diff --git a/migration/migration.c b/migration/migration.c index ab21de2cad..f0b70e8a9d 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1326,17 +1326,19 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_savevm_state_cleanup(); + bql_unlock(); + if (s->migration_thread_running) { + qemu_thread_join(&s->thread); + s->migration_thread_running = false; + } + bql_lock(); + + close_return_path_on_source(s); + if (s->to_dst_file) { QEMUFile *tmp; trace_migrate_fd_cleanup(); - bql_unlock(); - if (s->migration_thread_running) { - qemu_thread_join(&s->thread); - s->migration_thread_running = false; - } - bql_lock(); - multifd_send_shutdown(); qemu_mutex_lock(&s->qemu_file_lock); tmp = s->to_dst_file; @@ -1350,12 +1352,6 @@ static void migrate_fd_cleanup(MigrationState *s) qemu_fclose(tmp); } - /* - * We already cleaned up to_dst_file, so errors from the return - * path might be due to that, ignore them. - */ - close_return_path_on_source(s); - assert(!migration_is_active(s)); if (s->state == MIGRATION_STATUS_CANCELLING) { @@ -2874,6 +2870,13 @@ static MigThrError postcopy_pause(MigrationState *s) while (true) { QEMUFile *file; + /* + * We're already pausing, so ignore any errors on the return + * path and just wait for the thread to finish. It will be + * re-created when we resume. + */ + close_return_path_on_source(s); + /* * Current channel is possibly broken. Release it. Note that this is * guaranteed even without lock because to_dst_file should only be @@ -2893,13 +2896,6 @@ static MigThrError postcopy_pause(MigrationState *s) qemu_file_shutdown(file); qemu_fclose(file); - /* - * We're already pausing, so ignore any errors on the return - * path and just wait for the thread to finish. It will be - * re-created when we resume. - */ - close_return_path_on_source(s); - migrate_set_state(&s->state, s->state, MIGRATION_STATUS_POSTCOPY_PAUSED); -- 2.35.3
