The man page for the mq_open(2) function fails to state that another possible cause of the return value being set to -1, with error set to EINVAL, is that the call, if permitted, would cause one or another of the following kernel tunable limit parameters to be exceeded:
I created a Phabricator review for this:
This documents the error case and the sysctls for mqueue.
I'm not sure if this system call page is the right place
to document sysctls.
I disagree. As a general matter, all possible causes of syscall failures should be documented on the relevant man page (for the syscall).