Thread: pgsql: Allow WaitLatch() to be used without a latch.

Allow WaitLatch() to be used without a latch.

Due to flaws in commit 3347c982bab, using WaitLatch() without
WL_LATCH_SET could cause an assertion failure or crash.  Repair.

While here, also add a check that the latch we're switching to belongs
to this backend, when changing from one latch to another.

Discussion: https://postgr.es/m/CA%2BhUKGK1607VmtrDUHQXrsooU%3Dap4g4R2yaoByWOOA3m8xevUQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/733fa9aa51c526582f100aa0d375e0eb9a6bce8b

Modified Files
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src/backend/storage/ipc/latch.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)