mutex_init() — Apollo

MUTEX_$INIT                       Domain/OS                        MUTEX_$INIT


NAME
     mutex_$init - initialize a mutual exclusion lock record

SYNOPSIS (C)
     #include <apollo/base.h>
     #include <apollo/mutex.h>

     extern void mutex_$init(mutex_$lock_rec_t *lock_record)

SYNOPSIS (Pascal)
     %include '/sys/ins/base.ins.pas';
     %include '/sys/ins/mutex.ins.pas';

     procedure mutex_$init(out lock_record: mutex_$lock_rec_t);

SYNOPSIS (FORTRAN)
     %include '/sys/ins/base.ins.ftn'
     %include '/sys/ins/mutex.ins.ftn'

           integer*2 lock_record(4), lock_ec_awaiters
           integer*4 lock_ec_value
           character*1 lock_byte

           equivalence (lock_byte, lock_record(1))
           equivalence (lock_ec_value, lock_record(2))
           equivalence (lock_ec_awaiters, lock_record(4))

           call mutex_$init(lock_record)


DESCRIPTION
     Mutex_$init initializes a mutual exclusion lock record.  An initialized
     mutual exclusion lock record must be mapped into the address space of all
     processes using the lock.  The object of the mutual exclusion lock and
     the lock record itself, and any other data shared by the processes using
     the lock, may be mapped in the same object.

     This is the usual way to initialize a mutual exclusion lock record:

          1.   Map a file large enough to hold a lock record with an exclusive
               write lock to ensure that the map will fail if another process
               simultaneously attempts to initialize the lock record by map-
               ping the file the same way.

          2.   Call mutex_$init to initialize the lock record and register its
               eventcount with the system.

          3.   Remap or relock the lock record object so that other processes
               can map it for shared write access.

     lock_record
          A mutual exclusion lock record.

SEE ALSO
     ms_$crmapl, ms_$relock, and ms_$remap.
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