Re: Crash after a call to pg_backup_start()

On Fri, Oct 21, 2022 at 05:53:25PM +0800, Richard Guo wrote:
> Yeah, the two conditions could be both false. How about we update the
> comment a bit to emphasize this? Such as
>
> /* At most one of these conditions can be true */
> or
> /* These conditions can not be both true */

If you do that, it would be a bit easier to read as of the following
assertion instead? Like:
Assert(!during_backup_start ||
sessionBackupState == SESSION_BACKUP_NONE);

Please note that I have not checked in details all the interactions
behind register_persistent_abort_backup_handler() before entering in
do_pg_backup_start() and the ERROR_CLEANUP block used in this
routine (just a matter of some elog(ERROR)s put here and there, for
example). Anyway, yes, both conditions can be false, and that's easy
to reproduce:
1) Do pg_backup_start().
2) Do pg_backup_stop().
3) Stop the session to kick do_pg_abort_backup()
4) Assert()-boom.
--
Michael