Both shm_mq.c and nodeGather.c contain instances of this coding pattern:
WaitLatch(MyLatch, WL_LATCH_SET, 0); CHECK_FOR_INTERRUPTS(); ResetLatch(MyLatch);
I believe this is wrong and the CHECK_FOR_INTERRUPTS needs to be before
or after the two latch operations. As-is, if the reason somebody set
our latch was to get us to notice that a CHECK_FOR_INTERRUPTS condition
happened, there's a race condition where we'd fail to realize that.
Other places such as ProcWaitForSignal() do it that way; only recently
introduced (and unproven in the field) code has it like this.
Anyone want to argue it's okay as-is?
regards, tom lane