Question on LWLockMode in dsa.c

Hi,

While working on radix tree patch[1], John Naylor found that dsa.c
doesn't already use shared locks even in dsa_dump(). dsa_dump() seems
a pure read-only function so I thought we could use a shared lock mode
there. Is there any reason to use exclusive mode even in dsa_dump()?

Ultimately, since we're trying to add a new function
dsa_get_total_size() that just returns
dsa_area_control.total_segment_size and therefore would also be a
read-only function, I'd like to find out the correct lock mode there.

Regards,

[1] https://www.postgresql.org/message-id/CANWCAZYYzoKp_4%2B1m5mn-TRD62BTwom8iLXLOWMsHkkwFi%3Drzg%40mail.gmail.com

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Masahiko Sawada
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