pgsql: Prevent lwlock dtrace probes from unnecessary work

Prevent lwlock dtrace probes from unnecessary work

If dtrace is compiled in but disabled, the lwlock dtrace probes still
evaluate their arguments.  Since PostgreSQL 13, T_NAME(lock) does
nontrivial work, so it should be avoided if not needed.  To fix, make
these calls conditional on the *_ENABLED() macro corresponding to each
probe.

Reviewed-by: Craig Ringer <craig.ringer@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/CAGRY4nwxKUS_RvXFW-ugrZBYxPFFM5kjwKT5O+0+Stuga5b4+Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b94409a02f6122d77b5154e481c0819fed6b4c95

Modified Files
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src/backend/storage/lmgr/lwlock.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)