The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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

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    1 /*      $OpenBSD: lock.h,v 1.18 2007/04/12 22:20:14 thib Exp $  */
    2 
    3 /* 
    4  * Copyright (c) 1995
    5  *      The Regents of the University of California.  All rights reserved.
    6  *
    7  * This code contains ideas from software contributed to Berkeley by
    8  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
    9  * System project at Carnegie-Mellon University.
   10  *
   11  * Redistribution and use in source and binary forms, with or without
   12  * modification, are permitted provided that the following conditions
   13  * are met:
   14  * 1. Redistributions of source code must retain the above copyright
   15  *    notice, this list of conditions and the following disclaimer.
   16  * 2. Redistributions in binary form must reproduce the above copyright
   17  *    notice, this list of conditions and the following disclaimer in the
   18  *    documentation and/or other materials provided with the distribution.
   19  * 3. Neither the name of the University nor the names of its contributors
   20  *    may be used to endorse or promote products derived from this software
   21  *    without specific prior written permission.
   22  *
   23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   33  * SUCH DAMAGE.
   34  *
   35  *      @(#)lock.h      8.12 (Berkeley) 5/19/95
   36  */
   37 
   38 #ifndef _LOCK_H_
   39 #define _LOCK_H_
   40 
   41 #include <sys/simplelock.h>
   42 
   43 typedef struct simplelock       simple_lock_data_t;
   44 typedef struct simplelock       *simple_lock_t;
   45 typedef struct lock             lock_data_t;
   46 typedef struct lock             *lock_t;
   47 
   48 /*
   49  * The general lock structure.  Provides for multiple shared locks,
   50  * upgrading from shared to exclusive, and sleeping until the lock
   51  * can be gained. The simple locks are defined in <machine/param.h>.
   52  */
   53 struct lock {
   54         u_int   lk_flags;               /* see below */
   55         int     lk_sharecount;          /* # of accepted shared locks */
   56         int     lk_waitcount;           /* # of processes sleeping for lock */
   57         int     lk_exclusivecount;      /* # of recursive exclusive locks */
   58 
   59         /*
   60          * This is the sleep message for sleep locks, and a simple name
   61          * for spin locks.
   62          */
   63         char    *lk_wmesg;              /* resource sleeping (for tsleep) */
   64 
   65         /* pid of exclusive lock holder */
   66         pid_t lk_lockholder;
   67 
   68         /* priority at which to sleep */
   69         int lk_prio;
   70 
   71         /* maximum sleep time (for tsleep) */
   72         int lk_timo;
   73 
   74 #if defined(LOCKDEBUG)
   75         const char *lk_lock_file;
   76         const char *lk_unlock_file;
   77         int lk_lock_line;
   78         int lk_unlock_line;
   79 #endif
   80 };
   81 
   82 /*
   83  * Lock request types:
   84  *   LK_SHARED - get one of many possible shared locks. If a process
   85  *      holding an exclusive lock requests a shared lock, the exclusive
   86  *      lock(s) will be downgraded to shared locks.
   87  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
   88  *      grant a pending upgrade if it exists, then grant an exclusive
   89  *      lock. Only one exclusive lock may exist at a time, except that
   90  *      a process holding an exclusive lock may get additional exclusive
   91  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
   92  *      request, or if the LK_CANRECUSE flag was set when the lock was
   93  *      initialized.
   94  *   LK_RELEASE - release one instance of a lock.
   95  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
   96  *      decommissioned. This feature is used before freeing a lock that
   97  *      is part of a piece of memory that is about to be freed.
   98  *
   99  * These are flags that are passed to the lockmgr routine.
  100  */
  101 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
  102 #define LK_SHARED       0x00000001      /* shared lock */
  103 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
  104 #define LK_RELEASE      0x00000006      /* release any type of lock */
  105 #define LK_DRAIN        0x00000007      /* wait for all lock activity to end */
  106 /*
  107  * External lock flags.
  108  *
  109  * The first three flags may be set in lock_init to set their mode permanently,
  110  * or passed in as arguments to the lock manager.
  111  */
  112 #define LK_EXTFLG_MASK  0x00200070      /* mask of external flags */
  113 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
  114 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
  115 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
  116 #define LK_RECURSEFAIL  0x00200000      /* fail if recursive exclusive lock */
  117 /*
  118  * Internal lock flags.
  119  *
  120  * These flags are used internally to the lock manager.
  121  */
  122 #define LK_WANT_EXCL    0x00002000      /* exclusive lock sought */
  123 #define LK_HAVE_EXCL    0x00004000      /* exclusive lock obtained */
  124 #define LK_WAITDRAIN    0x00008000      /* process waiting for lock to drain */
  125 #define LK_DRAINING     0x00040000      /* lock is being drained */
  126 #define LK_DRAINED      0x00080000      /* lock has been decommissioned */
  127 /*
  128  * Control flags
  129  *
  130  * Non-persistent external flags.
  131  */
  132 #define LK_RETRY        0x00020000      /* vn_lock: retry until locked */
  133 
  134 /*
  135  * Lock return status.
  136  *
  137  * Successfully obtained locks return 0. Locks will always succeed
  138  * unless one of the following is true:
  139  *      LK_NOWAIT is set and a sleep would be required (returns EBUSY).
  140  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
  141  *      PCATCH is set in lock priority and a signal arrives (returns
  142  *          either EINTR or ERESTART if system calls is to be restarted).
  143  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
  144  * A failed lock attempt always returns a non-zero error value. No lock
  145  * is held after an error return.
  146  */
  147 
  148 /*
  149  * Indicator that no process holds exclusive lock
  150  */
  151 #define LK_KERNPROC ((pid_t) -2)
  152 #define LK_NOPROC ((pid_t) -1)
  153 #define LK_NOCPU ((cpuid_t) -1)
  154 
  155 struct proc;
  156 
  157 void    lockinit(struct lock *, int prio, char *wmesg, int timo,
  158                         int flags);
  159 int     lockmgr(__volatile struct lock *, u_int flags, struct simplelock *);
  160 void    lockmgr_printinfo(__volatile struct lock *);
  161 int     lockstatus(struct lock *);
  162 
  163 #if defined(LOCKDEBUG)
  164 int     _spinlock_release_all(__volatile struct lock *, const char *, int);
  165 void    _spinlock_acquire_count(__volatile struct lock *, int, const char *,
  166             int);
  167 
  168 #define spinlock_release_all(l) _spinlock_release_all((l), __FILE__, __LINE__)
  169 #define spinlock_acquire_count(l, c) _spinlock_acquire_count((l), (c),  \
  170                                         __FILE__, __LINE__)
  171 #else
  172 int     spinlock_release_all(__volatile struct lock *);
  173 void    spinlock_acquire_count(__volatile struct lock *, int);
  174 #endif
  175 
  176 #ifdef LOCKDEBUG
  177 #define LOCK_ASSERT(x)  KASSERT(x)
  178 #else
  179 #define LOCK_ASSERT(x)  /* nothing */
  180 #endif
  181 
  182 #if !defined(MULTIPROCESSOR)
  183 /*
  184  * XXX Simplelock macros used at "trusted" places.
  185  */
  186 #define SIMPLELOCK              simplelock
  187 #define SIMPLE_LOCK_INIT        simple_lock_init
  188 #define SIMPLE_LOCK             simple_lock
  189 #define SIMPLE_UNLOCK           simple_unlock
  190 #endif
  191 
  192 #endif /* !_LOCK_H_ */

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