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

     /* 
      * Copyright (c) 1995
      *      The Regents of the University of California.  All rights reserved.
      * Copyright (c) 2013
      *      The DragonFly Project.  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.
     */
    
    #ifndef _SYS_LOCK_H_
    #define _SYS_LOCK_H_
    
    /*
     * A number of third party programs #include <sys/lock.h> for no good
     * reason.  Don't actually include anything unless we are the kernel. 
     */
    #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
    
    #include <machine/lock.h>
    #ifndef _SYS_THREAD_H_
    #include <sys/thread.h>         /* lwkt_token */
    #endif
    #ifndef _SYS_SPINLOCK_H_
    #include <sys/spinlock.h>
    #endif
    
    /*
     * The general lock structure.  Provides for multiple shared locks,
     * upgrading from shared to exclusive, and sleeping until the lock
     * can be gained.
     */
    struct thread;
    
    struct lock {
            u_int   lk_flags;               /* see below */
            int     lk_count;               /* -shared, +exclusive */
            int     lk_timo;                /* maximum sleep time (for tsleep) */
            const char *lk_wmesg;           /* resource sleeping (for tsleep) */
            struct thread *lk_lockholder;   /* thread of excl 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_EXCLOTHER - return for lockstatus().  Used when another process
    *      holds the lock exclusively.
    *
    * 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_WAITUPGRADE  0x00000007
   #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
   
   /*
    * lk_count bit fields.
    *
    * Positive count is exclusive, negative count is shared.
    */
   #define LKC_EXREQ       0x80000000      /* waiting for exclusive lock */
   #define LKC_SHREQ       0x40000000      /* waiting for shared lock */
   #define LKC_UPREQ       0x20000000      /* waiting for upgrade */
   #define LKC_EXCL        0x10000000      /* exclusive (else shr or unlcoked) */
   #define LKC_UPGRANT     0x08000000      /* upgrade granted */
   #define LKC_MASK        0x07FFFFFF
   
   /*
    * 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.
    */
   #define LK_EXTFLG_MASK  0x07000070      /* 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_UNUSED0080   0x00000080
   #define LK_UNUSED0100x  0x01000000
   #define LK_TIMELOCK     0x02000000
   #define LK_PCATCH       0x04000000      /* timelocked with signal catching */
   
   /*
    * Control flags
    *
    * Non-persistent external flags.
    */
   #define LK_FAILRECLAIM  0x00010000 /* vn_lock: allowed to fail on reclaim */
   #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
   #define LK_UNUSED40000  0x00040000
   #define LK_UNUSED80000  0x00080000
   
   /*
    * 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_KERNTHREAD ((struct thread *)-2)
   #define LK_NOTHREAD ((struct thread *)-1)
   
   #ifdef _KERNEL
   
   void dumplockinfo(struct lock *lkp);
   struct proc;
   
   struct lock_args {
           struct lock     *la_lock;
           const char      *la_desc;
           int             la_flags;
   };
   
   void    lockinit (struct lock *, const char *wmesg, int timo, int flags);
   void    lockreinit (struct lock *, const char *wmesg, int timo, int flags);
   void    lockuninit(struct lock *);
   void    lock_sysinit(struct lock_args *);
   #ifdef DEBUG_LOCKS
   int     debuglockmgr (struct lock *, u_int flags,
                           const char *,
                           const char *,
                           int);
   #define lockmgr(lockp, flags) \
           debuglockmgr((lockp), (flags), "lockmgr", __FILE__, __LINE__)
   #else
   int     lockmgr (struct lock *, u_int flags);
   #endif
   void    lockmgr_setexclusive_interlocked(struct lock *);
   void    lockmgr_clrexclusive_interlocked(struct lock *);
   void    lockmgr_kernproc (struct lock *);
   void    lockmgr_printinfo (struct lock *);
   int     lockstatus (struct lock *, struct thread *);
   int     lockowned (struct lock *);
   int     lockcount (struct lock *);
   int     lockcountnb (struct lock *);
   
   #define LOCK_SYSINIT(name, lock, desc, flags)                           \
           static struct lock_args name##_args = {                         \
                   (lock),                                                 \
                   (desc),                                                 \
                   (flags)                                                 \
           };                                                              \
           SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,   \
               lock_sysinit, &name##_args);                                        \
           SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,       \
               lockuninit, (lock))
   
   #endif /* _KERNEL */
   #endif /* _KERNEL || _KERNEL_STRUCTURES */
   #endif /* _SYS_LOCK_H_ */

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