>> However, while at it, there is also the question of whether the control file
>> should be locked when updated, eg with flock(2) to avoid race conditions
>> between concurrent commands. ISTM that there is currently not such thing in
>> the code, but that it would be desirable.
>
> Shouldn't be necessary - the control file fits into a single page, and
> writes of that size ought to always be atomic. And I also think
> introducing flock usage for this would be quite disproportional.
Ok, fine.
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.
--
Fabien.