FreeBSD/Linux Kernel Cross Reference
sys/sys/lock.h

     /* 
      * Copyright (c) 1995
      *      The Regents of the University of California.  All rights reserved.
      *
      * This code contains ideas from software contributed to Berkeley by
      * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
      * System project at Carnegie-Mellon University.
      *
      * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)lock.h      8.12 (Berkeley) 5/19/95
     * $FreeBSD$
     */
    
    #ifndef _LOCK_H_
    #define _LOCK_H_
    
    
    #include <machine/lock.h>
    
    /*
     * The general lock structure.  Provides for multiple shared locks,
     * upgrading from shared to exclusive, and sleeping until the lock
     * can be gained. The simple locks are defined in <machine/param.h>.
     */
    struct lock {
            struct  simplelock lk_interlock; /* lock on remaining fields */
            u_int   lk_flags;               /* see below */
            int     lk_sharecount;          /* # of accepted shared locks */
            int     lk_waitcount;           /* # of processes sleeping for lock */
            short   lk_exclusivecount;      /* # of recursive exclusive locks */
            short   lk_prio;                /* priority at which to sleep */
            char    *lk_wmesg;              /* resource sleeping (for tsleep) */
            int     lk_timo;                /* maximum sleep time (for tsleep) */
            pid_t   lk_lockholder;          /* pid of exclusive lock holder */
    #ifdef  DEBUG_LOCKS
            const char *lk_filename;
            const char *lk_lockername;
            int     lk_lineno;
    #endif
    };
    /*
     * Lock request types:
     *   LK_SHARED - get one of many possible shared locks. If a process
     *      holding an exclusive lock requests a shared lock, the exclusive
     *      lock(s) will be downgraded to shared locks.
     *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
     *      grant a pending upgrade if it exists, then grant an exclusive
     *      lock. Only one exclusive lock may exist at a time, except that
     *      a process holding an exclusive lock may get additional exclusive
     *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
     *      request, or if the LK_CANRECUSE flag was set when the lock was
     *      initialized.
     *   LK_UPGRADE - the process must hold a shared lock that it wants to
     *      have upgraded to an exclusive lock. Other processes may get
     *      exclusive access to the resource between the time that the upgrade
     *      is requested and the time that it is granted.
     *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
     *      have upgraded to an exclusive lock. If the request succeeds, no
     *      other processes will have gotten exclusive access to the resource
     *      between the time that the upgrade is requested and the time that
     *      it is granted. However, if another process has already requested
     *      an upgrade, the request will fail (see error returns below).
     *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
     *      to have downgraded to a shared lock. If the process holds multiple
     *      (recursive) exclusive locks, they will all be downgraded to shared
     *      locks.
     *   LK_RELEASE - release one instance of a lock.
     *   LK_DRAIN - wait for all activity on the lock to end, then mark it
     *      decommissioned. This feature is used before freeing a lock that
     *      is part of a piece of memory that is about to be freed.
     *
     * These are flags that are passed to the lockmgr routine.
    */
   #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
   #define LK_SHARED       0x00000001      /* shared lock */
   #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
   #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
   #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
   #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
   #define LK_RELEASE      0x00000006      /* release any type of lock */
   #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
   /*
    * External lock flags.
    *
    * The first three flags may be set in lock_init to set their mode permanently,
    * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
    * set only at the release of a lock obtained by drain.
    */
   #define LK_EXTFLG_MASK  0x01000070      /* mask of external flags */
   #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
   #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
   #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
   #define LK_REENABLE     0x00000080      /* lock is be reenabled after drain */
   #define LK_NOPAUSE      0x01000000      /* no spinloop */
   /*
    * Internal lock flags.
    *
    * These flags are used internally to the lock manager.
    */
   #define LK_WANT_UPGRADE 0x00000100      /* waiting for share-to-excl upgrade */
   #define LK_WANT_EXCL    0x00000200      /* exclusive lock sought */
   #define LK_HAVE_EXCL    0x00000400      /* exclusive lock obtained */
   #define LK_WAITDRAIN    0x00000800      /* process waiting for lock to drain */
   #define LK_DRAINING     0x00004000      /* lock is being drained */
   #define LK_DRAINED      0x00008000      /* lock has been decommissioned */
   /*
    * Control flags
    *
    * Non-persistent external flags.
    */
   #define LK_INTERLOCK    0x00010000 /* unlock passed simple lock after
                                      getting lk_interlock */
   #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
   #define LK_NOOBJ        0x00040000 /* vget: don't create object */
   
   /*
    * Internal state flags corresponding to lk_sharecount, and lk_waitcount
    */
   #define LK_SHARE_NONZERO 0x00100000
   #define LK_WAIT_NONZERO  0x00200000
   
   /*
    * Lock return status.
    *
    * Successfully obtained locks return 0. Locks will always succeed
    * unless one of the following is true:
    *      LK_FORCEUPGRADE is requested and some other process has already
    *          requested a lock upgrade (returns EBUSY).
    *      LK_WAIT is set and a sleep would be required (returns EBUSY).
    *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
    *      PCATCH is set in lock priority and a signal arrives (returns
    *          either EINTR or ERESTART if system calls is to be restarted).
    *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
    * A failed lock attempt always returns a non-zero error value. No lock
    * is held after an error return (in particular, a failed LK_UPGRADE
    * or LK_FORCEUPGRADE will have released its shared access lock).
    */
   
   /*
    * Indicator that no process holds exclusive lock
    */
   #define LK_KERNPROC ((pid_t) -2)
   #define LK_NOPROC ((pid_t) -1)
   
   void dumplockinfo(struct lock *lkp);
   struct proc;
   
   void    lockinit __P((struct lock *, int prio, char *wmesg, int timo,
                           int flags));
   #ifdef DEBUG_LOCKS
   int     debuglockmgr __P((struct lock *, u_int flags,
                           struct simplelock *, struct proc *p,
                           const char *,
                           const char *,
                           int));
   #define lockmgr(lockp, flags, slockp, proc) \
           debuglockmgr((lockp), (flags), (slockp), (proc), \
               "lockmgr", __FILE__, __LINE__)
   #else
   int     lockmgr __P((struct lock *, u_int flags,
                           struct simplelock *, struct proc *p));
   #endif
   void    lockmgr_printinfo __P((struct lock *));
   int     lockstatus __P((struct lock *));
   
   #ifdef SIMPLELOCK_DEBUG
   void _simple_unlock __P((struct simplelock *alp, const char *, int));
   #define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
   int _simple_lock_try __P((struct simplelock *alp, const char *, int));
   #define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
   void _simple_lock __P((struct simplelock *alp, const char *, int));
   #define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
   void simple_lock_init __P((struct simplelock *alp));
   #else /* !SIMPLELOCK_DEBUG */
   #if NCPUS == 1 /* no multiprocessor locking is necessary */
   #define NULL_SIMPLELOCKS
   #define simple_lock_init(alp)
   #define simple_lock(alp)
   #define simple_lock_try(alp)    (1)     /* always succeeds */
   #define simple_unlock(alp)
   #endif /* NCPUS == 1 */
   #endif /* !SIMPLELOCK_DEBUG */
   
   #endif /* !_LOCK_H_ */

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