[dimitri]

Summary

LatchWait() -- the sole sleep point in both the health-check launcher's and every per-database health-check worker's main loop -- calls WaitLatch() + ResetLatch() but never CHECK_FOR_INTERRUPTS().

A background worker only acknowledges a ProcSignalBarrier (the mechanism DROP DATABASE uses to wait until every backend in the cluster has released smgr state) from inside CHECK_FOR_INTERRUPTS() -- WaitLatch() wakes the process up on the pending signal, but doesn't process it itself.

Practical effect: as long as any pgautofailover health-check worker is running anywhere in the cluster (which is always, by default, once the extension is loaded via shared_preload_libraries), every DROP DATABASE statement anywhere in that cluster blocks forever, repeatedly logging:

LOG:  still waiting for backend with PID ... to accept ProcSignalBarrier
STATEMENT:  DROP DATABASE IF EXISTS "..."

This includes pg_regress's own schedule setup, so make installcheck against a live Postgres 17 instance hangs indefinitely before running a single test.

Root cause

health_check_worker.c's LatchWait() is the common per-iteration sleep point for both worker loops. Standard Postgres background worker loops call CHECK_FOR_INTERRUPTS() right after waking from WaitLatch()/ResetLatch() precisely so that pending interrupts -- including a ProcSignalBarrier -- get processed promptly. This worker never did.

Fix

Add CHECK_FOR_INTERRUPTS() right after ResetLatch() in LatchWait(), matching the idiom used by every other Postgres background worker.

Reproduction / verification

Reproduces on an unmodified checkout against Postgres 17.11: CREATE DATABASE and ordinary queries work fine, but any DROP DATABASE against a cluster with shared_preload_libraries = 'pgautofailover' loaded hangs forever once the extension's health-check worker has started.

With the fix: rebuilt and reinstalled the extension against a live PG17.11 instance; the full monitor regression schedule (20 tests) and isolation test suite (6 tests) now complete and pass via make installcheck, where they previously hung.

Test plan

• make installcheck completes (was hanging indefinitely before this fix)
• All existing monitor regression tests still pass
• All existing isolation tests still pass