Kris Kennaway <kris@obsecurity.org> writes:
> I have not studied the exact code path, but there are indeed multiple
> wakeups happening from the semaphore code (as many as the number of
> active postgresql processes). It is easy to instrument
> sleepq_broadcast() and log them when they happen.
There are certainly cases where Postgres will wake up a number of
processes in quick succession, but that should happen from a separate
semop() kernel call, on a different semaphore, for each such process.
If there's really multiple processes being released by the same semop()
then there's a bug we need to look into (or maybe it's a kernel bug?).
Anyway I'd be interested to know what the test case is, and which PG
version you were testing.
regards, tom lane