Hello Andres,
>> Note that my concern is not about the page size, but rather that as more
>> commands may change the cluster status by editing the control file, it would
>> be better that a postmaster does not start while a pg_rewind or enable
>> checksum or whatever is in progress, and currently there is a possible race
>> condition between the read and write that can induce an issue, at least
>> theoretically.
>
> Seems odd to bring this up in this thread, it really has nothing to do
> with the topic.
Indeed. I raised it here because it is in the same area of code and
Michaël was looking at it.
> If we were to want to do more here, ISTM the right approach would use
> the postmaster pid file, not the control file.
ISTM that this just means re-inventing a manual poor-featured
race-condition-prone lock API around another file, which seems to be
created more or less only by "pg_ctl", while some other commands use the
control file (eg pg_rewind, AFAICS).
--
Fabien.