Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (A-B)
Guardian Procedure Calls Reference Manual—522629-013
2-58
BINSEM_CREATE_ Procedure
segment (PFS) has reached the maximum limit of available space. The
corresponding errno
value is EMFILE.
4028 No space. The processor has reached the maximum limit of space
available for binary semaphores. The corresponding
errno value is
ENOSPC.
semid output
INT (32) .EXT:ref:1
returns the binary semaphore ID.
security input
INT:value
specifies the binary semaphore security. The security determines which processes
on the same processor can open the binary semaphore. Values are:
0 Any. Any process.
1 Group. Any process with the same process access ID group as the binary
semaphore’s owner, or a process with the super ID (255,255).
2 Owner. Any process with the same process access ID (group and member) as
the binary semaphore’s owner, or a process with the super ID.
General Considerations for Binary Semaphores
•
Binary semaphore attributes
•
Owner. The owner of a binary semaphore is the process access ID of the
process that calls the BINSEM_CREATE_ procedure. The owner of a binary
semaphore is defined by a group number and a member number. The owner
is relevant only in the context of security; it is neither specified nor returned by
the binary semaphore procedures.
•
Security. The security of a binary semaphore determines whether it can be
opened by any process, a process belonging to the owner’s group, or a
process belonging to the owner. Once a binary semaphore has been created,
its security cannot be altered.
•
Identifying a binary semaphore
•
Binary semaphore ID. A binary semaphore ID identifies each instance of an
open of a binary semaphore. A binary semaphore can have multiple openers.
•
Process handle. A process handle is used in conjunction with a binary
semaphore ID to identify a binary semaphore opened by another process.
•
Three binary semaphore states
•
Locked. A binary semaphore can be locked by a process. Only one process
at a time can hold the lock on a binary semaphore.