| Message ID | 20171220031057.GC22308@xz-mi (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Peter Xu (peterx@redhat.com) wrote: > On Tue, Dec 19, 2017 at 11:33:21AM +0000, Dr. David Alan Gilbert wrote: > > * Peter Xu (peterx@redhat.com) wrote: > > > On Tue, Dec 19, 2017 at 10:14:08AM +0000, Dr. David Alan Gilbert wrote: > > > > * Peter Xu (peterx@redhat.com) wrote: > > > > > On Fri, Dec 15, 2017 at 05:16:53PM +0000, Dr. David Alan Gilbert (git) wrote: > > > > > > From: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > > > > > > > > > > > Hi, > > > > > > Where a channel fails asynchronously during connect, call > > > > > > back through the migration code so it can clean up. > > > > > > In particular this causes the transition of a 'cancelling' state > > > > > > to 'cancelled' in the case of: > > > > > > > > > > > > migrate -d tcp:deadhost:port > > > > > > <host tries to connect> > > > > > > migrate_cancel > > > > > > > > > > > > previously the status would get stuck in cancelling because > > > > > > the final cleanup didn't happen. > > > > > > > > > > > > This is the second part of the fix for: > > > > > > https://bugzilla.redhat.com/show_bug.cgi?id=1525899 > > > > > > > > > > IIUC this series tries to deliver the connection error a long way > > > > > until migrate_fd_connect() to handle it. But, haven't we already have > > > > > a function migrate_fd_error() to do that (which is faster, and > > > > > simpler)? > > > > > > > > > > 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); > > > > > migrate_set_error(s, error); > > > > > notifier_list_notify(&migration_state_notifiers, s); > > > > > block_cleanup_parameters(s); > > > > > } > > > > > > > > > > I think it's not handling the case when cancelling. If we let it to > > > > > handle the cancelling case well, would it be a simpler fix? > > > > > > > > > > Moreover, I think this is another good example that migration is not > > > > > handling the cleanup "cleanly" in general... I really hope we can do > > > > > this better in 2.12. I'll see whether I can give it a shot, but in > > > > > all cases it'll be after the merging of existing patches since there > > > > > are already quite a lot of dangling patches. > > > > > > > > No, I think migrate_fd_error is the cause of the problem here, not the > > > > answer. > > > > > > Could I ask why migrate_fd_error() is problematic? Yeah I agree that > > > we should have a single point to clean things up, then can we call > > > migrate_fd_cleanup() somehow inside migrate_fd_error()? > > > > > > The thing I don't really understand is: why we want the error be > > > delivered via those functions (migration_channel_connect, > > > migrate_fd_connect, etc.) to finally be cleaned up. > > > > migrate_fd_cleanup has a lot of code for dealing with different cases: > > a) Closing the to_dst_file > > b) joining the thread if its already running > > c) Cleaning up multifd (stub) > > d) finishing of cancel > > e) notification > > f) block cleanup > > > > we seem to have copied some of those into migrate_fd_error - but not all > > of them. In this case the one we're missing is (d) got finishing > > cancel; > > when you issue a cancel command we move from whatever state we were in > > to the 'cancelling' state, various things get cleaned up and eventually > > we move to cancelled; that wasn't happening because we missed the > > code in migrate_fd_cleanup out. So we could copy that code (copied code > > is bad) or we could just make sure migrate_fd_cleanup is called like > > it normally is. > > I fully agree on above. > > > > > The other thinking is that at the moment the migration/socket.c and tls.c > > etc code has to choose between callbacks into the main migration code, > > either migration_channel_connet or migrate_fd_error - now it's simpler, > > once you've asked for an outgoing migration you always get a callback > > to migration_channel_connect. Much more predictable. > > This is the point I still don't understand, on why we must go into > migrate_fd_connect(), even if error happens before that point. To me it just doesn't feel clean, and is the reason this error happened in the first place. Dave > What I meant is pasted at the end. Again, I don't know whether it > works, just want to show what I meant. I'm fine with current approach > too. Thanks, > > ---------------------------------- > > diff --git a/migration/migration.c b/migration/migration.c > index 4de3b551fe..fd9b509ab1 100644 > --- a/migration/migration.c > +++ b/migration/migration.c > @@ -1074,8 +1074,10 @@ static void migrate_fd_cleanup(void *opaque) > { > MigrationState *s = opaque; > > - qemu_bh_delete(s->cleanup_bh); > - s->cleanup_bh = NULL; > + if (s->cleanup_bh) { > + qemu_bh_delete(s->cleanup_bh); > + s->cleanup_bh = NULL; > + } > > if (s->to_dst_file) { > Error *local_err = NULL; > @@ -1124,11 +1126,15 @@ void migrate_fd_error(MigrationState *s, const Error *error) > { > trace_migrate_fd_error(error_get_pretty(error)); > assert(s->to_dst_file == NULL); > + /* > + * If we are still in setup, switch to failure. It's also > + * possible that the migration has been cancelled, then we do > + * nothing here. > + */ > migrate_set_state(&s->state, MIGRATION_STATUS_SETUP, > MIGRATION_STATUS_FAILED); > migrate_set_error(s, error); > - notifier_list_notify(&migration_state_notifiers, s); > - block_cleanup_parameters(s); > + migrate_fd_cleanup(s); > } > > static void migrate_fd_cancel(MigrationState *s) > > -- > Peter Xu -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
diff --git a/migration/migration.c b/migration/migration.c index 4de3b551fe..fd9b509ab1 100644 --- a/migration/migration.c +++ b/migration/migration.c @@ -1074,8 +1074,10 @@ static void migrate_fd_cleanup(void *opaque) { MigrationState *s = opaque; - qemu_bh_delete(s->cleanup_bh); - s->cleanup_bh = NULL; + if (s->cleanup_bh) { + qemu_bh_delete(s->cleanup_bh); + s->cleanup_bh = NULL; + } if (s->to_dst_file) { Error *local_err = NULL; @@ -1124,11 +1126,15 @@ void migrate_fd_error(MigrationState *s, const Error *error) { trace_migrate_fd_error(error_get_pretty(error)); assert(s->to_dst_file == NULL); + /* + * If we are still in setup, switch to failure. It's also + * possible that the migration has been cancelled, then we do + * nothing here. + */ migrate_set_state(&s->state, MIGRATION_STATUS_SETUP, MIGRATION_STATUS_FAILED); migrate_set_error(s, error); - notifier_list_notify(&migration_state_notifiers, s); - block_cleanup_parameters(s); + migrate_fd_cleanup(s); } static void migrate_fd_cancel(MigrationState *s)