actual file storing the semaphore object is different from the file
created on the first open. Store the file st_dev and st_ino members
of the struct stat in the semaphore structure on open, and compare
them with the attributes of the opened file to detect unlink and
re-creation.
This fixes an issue of sem_unlink(3) failing to flush the named entry
in the semaphore list for the current or remote process, making
sem_unlink(3) not correctly operating if the unlinked semaphore is
still opened.
Reported by: Joris Giovannangeli <joris@giovannangeli.fr>
PR: standards/189353
Reviewed by: jilles (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
ca5e4fe970