msem_lock(2)							System Calls Manual						      msem_lock(2)

NAME

       msem_lock() - lock a semaphore

SYNOPSIS


DESCRIPTION

       attempts to lock a binary semaphore.

       sem points to an structure which specifies the semaphore to be locked.

       If the semaphore is not currently locked, it becomes locked and the function returns successfully.

       If  the	semaphore is currently locked, and condition is then the function returns with an error.  If the semaphore is currently locked and
       condition is zero, the function does not return until either the calling process is able to successfully lock the semaphore,  or  an  error
       condition occurs.

       All calls to and by multiple processes sharing a common structure behave as if the calls were serialized.

       If  the	structure  contains any value not resulting from a call to followed by a (possibly empty) sequence of calls to and the results are
       undefined.  The address of an uniquely identifies the semaphore.  If the structure contains any value copied from an structure at a differ-
       ent address, the result is undefined.

IMPLEMENTATION NOTES

       If blocked on a locked semaphore, suspends the calling process at a priority such that the process can be interrupted by a signal.

       The system attempts to ignore or recover from invalid values written to the structure, but this is not guaranteed for all cases.

       successfully acquires a semaphore that is locked by a process that has exited.

RETURN VALUE

       returns one of the following values:

	      Success.

	      Failure.
		     is set to indicate the error.

ERRORS

       sets to one of the following values if the corresponding condition is encountered.

	      was specified and the semaphore was already locked.

	      sem	     points to an structure that has been removed, or condition is invalid.

	      was interrupted by a signal that was caught.

	      The semaphore is currently locked,
			     condition is zero, and waiting to lock the semaphore would create a deadlock.

	      sem	     is not a properly aligned address or is otherwise an invalid pointer.

AUTHOR

       was developed by HP and OSF.

SEE ALSO

       msem_init(2), msem_remove(2), msem_unlock(2), mman(5).

STANDARDS CONFORMANCE

																      msem_lock(2)