plock(2)                                                    plock(2)


       NAME
             plock - lock into memory or unlock process, text, or data

       SYNOPSIS
             #include <sys/lock.h>
             int plock(int op);

       DESCRIPTION
             plock allows the calling process to lock into memory or unlock
             its text segment (text lock), its data segment (data lock), or
             both its text and data segments (process lock).  Locked
             segments are immune to all routine swapping.  plock also
             allows these segments to be unlocked.  The effective user id
             of the calling process must have the P_PLOCK privilege to use
             this call.

             plock performs the function specified by op:

             PROCLOCK    Lock text and data segments into memory (process
                         lock).

             TXTLOCK     Lock text segment into memory (text lock).

             DATLOCK     Lock data segment into memory (data lock).

             UNLOCK      Remove locks.

          Return Values
             On success, plock returns 0.  On failure, plock returns -1 and
             sets errno to identify the error.

          Errors
             In the following conditions, plock fails and sets errno to:

             EPERM          The effective user id of the calling process
                            does not have the P_PLOCK privilege.

             EFAULT         The segment to be locked has been aborted (e.g.
                            by a file truncate operation), or pages
                            following the end of an object are not
                            allocated.

             EIO            An I/O error occurred when attempting to read
                            the page from a device or a network.




                           Copyright 1994 Novell, Inc.               Page 1

      plock(2)                                                    plock(2)


            EINVAL         op is equal to PROCLOCK and a process lock, a
                           text lock, or a data lock already exists on the
                           calling process.

            EINVAL         op is equal to TXTLOCK and a text lock, or a
                           process lock already exists on the calling
                           process.

            EINVAL         op is equal to DATLOCK and a data lock, or a
                           process lock already exists on the calling
                           process.

            EINVAL         op is equal to UNLOCK and no lock exists on the
                           calling process.

            EAGAIN         Not enough memory, or there is insufficient
                           resources.

      REFERENCES
            exec(2), exit(2), fork(2), memcntl(2)

      NOTICES
            memcntl is the preferred interface to memory locking.

         Considerations for Threads Programming
            Sibling threads share (by definition) the same address space;
            modifications to the address space by one can be perceived by
            the others.




















                          Copyright 1994 Novell, Inc.               Page 2