Re: race condition when writing pg_control - Mailing list pgsql-hackers

From Tom Lane
Subject Re: race condition when writing pg_control
Date
Msg-id 2138498.1715886091@sss.pgh.pa.us
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In response to Re: race condition when writing pg_control  (Andres Freund <andres@anarazel.de>)
Responses Re: race condition when writing pg_control
List pgsql-hackers
Andres Freund <andres@anarazel.de> writes:
> On 2024-05-16 14:50:50 -0400, Tom Lane wrote:
>> The intention was certainly always that it be atomic.  If it isn't
>> we have got *big* trouble.

> We unfortunately do *know* that on several systems e.g. basebackup can read a
> partially written control file, while the control file is being
> updated.

Yeah, but can't we just retry that if we get a bad checksum?

What had better be atomic is the write to disk.  Systems that can't
manage POSIX semantics for concurrent reads and writes are annoying,
but not fatal ...

            regards, tom lane



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