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6708e447ef
The logic around shm_mq_detach was a few bricks shy of a load, because (contrary to the comments for shm_mq_attach) all it did was update the shared shm_mq state. That left us leaking a bit of process-local memory, but much worse, the on_dsm_detach callback for shm_mq_detach was still armed. That means that whenever we ultimately detach from the DSM segment, we'd run shm_mq_detach again for already-detached, possibly long-dead queues. This accidentally fails to fail today, because we only ever re-use a shm_mq's memory for another shm_mq, and multiple detach attempts on the last such shm_mq are fairly harmless. But it's gonna bite us someday, so let's clean it up. To do that, change shm_mq_detach's API so it takes a shm_mq_handle not the underlying shm_mq. This makes the callers simpler in most cases anyway. Also fix a few places in parallel.c that were just pfree'ing the handle structs rather than doing proper cleanup. Back-patch to v10 because of the risk that the revenant shm_mq_detach callbacks would cause a live bug sometime. Since this is an API change, it's too late to do it in 9.6. (We could make a variant patch that preserves API, but I'm not excited enough to do that.) Discussion: https://postgr.es/m/8670.1504192177@sss.pgh.pa.us