pgsql: Acquire ControlFileLock in relevant SQL functions.

Acquire ControlFileLock in relevant SQL functions.

Commit dc7d70ea added functions that read the control file, but didn't
acquire ControlFileLock.  With unlucky timing, file systems that have
weak interlocking like ext4 and ntfs could expose partially overwritten
contents, and the checksum would fail.

Back-patch to all supported releases.

Reviewed-by: David Steele <[email protected]>
Reviewed-by: Anton A. Melnikov <[email protected]>
Reviewed-by: Michael Paquier <[email protected]>
Discussion: https://postgr.es/m/20221123014224.xisi44byq3cf5psi%40awork3.anarazel.de

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/637e86ecc5e4fcc5447b67d83337bc8752a40a52

Modified Files
--------------
src/backend/utils/misc/pg_controldata.c | 9 +++++++++
1 file changed, 9 insertions(+)