Re: [Qemu-devel] [PATCH v9 02/12] migration: Improve migration thread error handling

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Dr. David Alan Gilbert (dgilbert@redhat.com) wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
> > We now report errors also when we finish migration, not only on info
> > migrate.  We plan to use this error from several places, and we want
> > the first error to happen to win, so we add an mutex to order it.
> > 
> > Signed-off-by: Juan Quintela <quintela@redhat.com>
> > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> > ---
> >  migration/migration.c | 19 ++++++++++++++++---
> >  migration/migration.h |  7 ++++++-
> >  migration/tls.c       |  1 -
> >  3 files changed, 22 insertions(+), 5 deletions(-)
> > 
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 98429dc843..468f51cfa7 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -1071,19 +1071,30 @@ static void migrate_fd_cleanup(void *opaque)
> >                            MIGRATION_STATUS_CANCELLED);
> >      }
> >  
> > +    if (s->error) {
> > +        /* It is used on info migrate.  We can't free it */
> > +        error_report_err(error_copy(s->error));
> > +    }
> >      notifier_list_notify(&migration_state_notifiers, s);
> >      block_cleanup_parameters(s);
> >  }
> >  
> > +void migrate_set_error(MigrationState *s, const Error *error)
> 
> If you find you need to resend this, please add a comment on this
> function saying it takes a copy and it's upto the caller to free
> the error they pass in.

Oops, ignore that, I see you change it in the next one.

> Dave
> 
> > +{
> > +    qemu_mutex_lock(&s->error_mutex);
> > +    if (!s->error) {
> > +        s->error = error_copy(error);
> > +    }
> > +    qemu_mutex_unlock(&s->error_mutex);
> > +}
> > +
> >  void migrate_fd_error(MigrationState *s, const Error *error)
> >  {
> >      trace_migrate_fd_error(error_get_pretty(error));
> >      assert(s->to_dst_file == NULL);
> >      migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
> >                        MIGRATION_STATUS_FAILED);
> > -    if (!s->error) {
> > -        s->error = error_copy(error);
> > -    }
> > +    migrate_set_error(s, error);
> >      notifier_list_notify(&migration_state_notifiers, s);
> >      block_cleanup_parameters(s);
> >  }
> > @@ -2355,6 +2366,7 @@ static void migration_instance_finalize(Object *obj)
> >      MigrationState *ms = MIGRATION_OBJ(obj);
> >      MigrationParameters *params = &ms->parameters;
> >  
> > +    qemu_mutex_destroy(&ms->error_mutex);
> >      g_free(params->tls_hostname);
> >      g_free(params->tls_creds);
> >  }
> > @@ -2367,6 +2379,7 @@ static void migration_instance_init(Object *obj)
> >      ms->state = MIGRATION_STATUS_NONE;
> >      ms->xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE;
> >      ms->mbps = -1;
> > +    qemu_mutex_init(&ms->error_mutex);
> >  
> >      params->tls_hostname = g_strdup("");
> >      params->tls_creds = g_strdup("");
> > diff --git a/migration/migration.h b/migration/migration.h
> > index b83cceadc4..51c0ac2e71 100644
> > --- a/migration/migration.h
> > +++ b/migration/migration.h
> > @@ -129,8 +129,12 @@ struct MigrationState
> >      int64_t colo_checkpoint_time;
> >      QEMUTimer *colo_delay_timer;
> >  
> > -    /* The last error that occurred */
> > +    /* The first error that has occurred.
> > +       We used the mutex to be able to return the 1st error message */
> >      Error *error;
> > +    /* mutex to protect errp */
> > +    QemuMutex error_mutex;
> > +
> >      /* Do we have to clean up -b/-i from old migrate parameters */
> >      /* This feature is deprecated and will be removed */
> >      bool must_remove_block_options;
> > @@ -159,6 +163,7 @@ bool  migration_has_all_channels(void);
> >  
> >  uint64_t migrate_max_downtime(void);
> >  
> > +void migrate_set_error(MigrationState *s, const Error *error);
> >  void migrate_fd_error(MigrationState *s, const Error *error);
> >  
> >  void migrate_fd_connect(MigrationState *s);
> > diff --git a/migration/tls.c b/migration/tls.c
> > index 596e8790bd..026a008667 100644
> > --- a/migration/tls.c
> > +++ b/migration/tls.c
> > @@ -119,7 +119,6 @@ static void migration_tls_outgoing_handshake(QIOTask *task,
> >      if (qio_task_propagate_error(task, &err)) {
> >          trace_migration_tls_outgoing_handshake_error(error_get_pretty(err));
> >          migrate_fd_error(s, err);
> > -        error_free(err);
> >      } else {
> >          trace_migration_tls_outgoing_handshake_complete();
> >          migration_channel_connect(s, ioc, NULL);
> > -- 
> > 2.13.5
> > 
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK