Hi,
I was able to reproduce it in a read-write workload, instead of the
read-only workload you'd proposed.
On 2016-10-05 14:01:05 -0400, Tom Lane wrote:
> Curiously, I did not see such a hang with regular SysV semaphores.
> That may be just a timing thing, or it may have something to do with
> POSIX semaphores being actually futexes on this platform (so that there
> is state inside the process not outside it).
Without yet having analyzed this deeply, could it actually be that the
reason is that sem_post/wait aren't proper memory barriers? On a glance
the symptoms look like values have been modified without proper locks...
Greetings,
Andres Freund