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 /* 
    2  * Copyright (c) 1995
    3  *      The Regents of the University of California.  All rights reserved.
    4  * Copyright (c) 2013
    5  *      The DragonFly Project.  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. All advertising materials mentioning features or use of this software
   20  *    must display the following acknowledgement:
   21  *      This product includes software developed by the University of
   22  *      California, Berkeley and its contributors.
   23  * 4. Neither the name of the University nor the names of its contributors
   24  *    may be used to endorse or promote products derived from this software
   25  *    without specific prior written permission.
   26  *
   27  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   28  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   29  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   30  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   31  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   32  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   33  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   34  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   35  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   36  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   37  * SUCH DAMAGE.
   38  */
   39 
   40 #ifndef _SYS_LOCK_H_
   41 #define _SYS_LOCK_H_
   42 
   43 /*
   44  * A number of third party programs #include <sys/lock.h> for no good
   45  * reason.  Don't actually include anything unless we are the kernel. 
   46  */
   47 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
   48 
   49 #include <machine/lock.h>
   50 #ifndef _SYS_THREAD_H_
   51 #include <sys/thread.h>         /* lwkt_token */
   52 #endif
   53 #ifndef _SYS_SPINLOCK_H_
   54 #include <sys/spinlock.h>
   55 #endif
   56 
   57 /*
   58  * The general lock structure.  Provides for multiple shared locks,
   59  * upgrading from shared to exclusive, and sleeping until the lock
   60  * can be gained.
   61  */
   62 struct thread;
   63 
   64 struct lock {
   65         u_int   lk_flags;               /* see below */
   66         int     lk_count;               /* -shared, +exclusive */
   67         int     lk_timo;                /* maximum sleep time (for tsleep) */
   68         const char *lk_wmesg;           /* resource sleeping (for tsleep) */
   69         struct thread *lk_lockholder;   /* thread of excl lock holder */
   70 #ifdef  DEBUG_LOCKS
   71         const char *lk_filename;
   72         const char *lk_lockername;
   73         int     lk_lineno;
   74 #endif
   75 };
   76 
   77 /*
   78  * Lock request types:
   79  *   LK_SHARED - get one of many possible shared locks. If a process
   80  *      holding an exclusive lock requests a shared lock, the exclusive
   81  *      lock(s) will be downgraded to shared locks.
   82  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
   83  *      grant a pending upgrade if it exists, then grant an exclusive
   84  *      lock. Only one exclusive lock may exist at a time, except that
   85  *      a process holding an exclusive lock may get additional exclusive
   86  *      locks if it explicitly sets the LK_CANRECURSE flag in the lock
   87  *      request, or if the LK_CANRECUSE flag was set when the lock was
   88  *      initialized.
   89  *   LK_UPGRADE - the process must hold a shared lock that it wants to
   90  *      have upgraded to an exclusive lock. Other processes may get
   91  *      exclusive access to the resource between the time that the upgrade
   92  *      is requested and the time that it is granted.
   93  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
   94  *      have upgraded to an exclusive lock. If the request succeeds, no
   95  *      other processes will have gotten exclusive access to the resource
   96  *      between the time that the upgrade is requested and the time that
   97  *      it is granted. However, if another process has already requested
   98  *      an upgrade, the request will fail (see error returns below).
   99  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
  100  *      to have downgraded to a shared lock. If the process holds multiple
  101  *      (recursive) exclusive locks, they will all be downgraded to shared
  102  *      locks.
  103  *   LK_RELEASE - release one instance of a lock.
  104  *   LK_EXCLOTHER - return for lockstatus().  Used when another process
  105  *      holds the lock exclusively.
  106  *
  107  * These are flags that are passed to the lockmgr routine.
  108  */
  109 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
  110 #define LK_SHARED       0x00000001      /* shared lock */
  111 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
  112 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
  113 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
  114 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
  115 #define LK_RELEASE      0x00000006      /* release any type of lock */
  116 #define LK_WAITUPGRADE  0x00000007
  117 #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
  118 
  119 /*
  120  * lk_count bit fields.
  121  *
  122  * Positive count is exclusive, negative count is shared.
  123  */
  124 #define LKC_EXREQ       0x80000000      /* waiting for exclusive lock */
  125 #define LKC_SHREQ       0x40000000      /* waiting for shared lock */
  126 #define LKC_UPREQ       0x20000000      /* waiting for upgrade */
  127 #define LKC_EXCL        0x10000000      /* exclusive (else shr or unlcoked) */
  128 #define LKC_UPGRANT     0x08000000      /* upgrade granted */
  129 #define LKC_MASK        0x07FFFFFF
  130 
  131 /*
  132  * External lock flags.
  133  *
  134  * The first three flags may be set in lock_init to set their mode permanently,
  135  * or passed in as arguments to the lock manager.
  136  */
  137 #define LK_EXTFLG_MASK  0x07000070      /* mask of external flags */
  138 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
  139 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
  140 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
  141 #define LK_UNUSED0080   0x00000080
  142 #define LK_UNUSED0100x  0x01000000
  143 #define LK_TIMELOCK     0x02000000
  144 #define LK_PCATCH       0x04000000      /* timelocked with signal catching */
  145 
  146 /*
  147  * Control flags
  148  *
  149  * Non-persistent external flags.
  150  */
  151 #define LK_FAILRECLAIM  0x00010000 /* vn_lock: allowed to fail on reclaim */
  152 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
  153 #define LK_UNUSED40000  0x00040000
  154 #define LK_UNUSED80000  0x00080000
  155 
  156 /*
  157  * Lock return status.
  158  *
  159  * Successfully obtained locks return 0. Locks will always succeed
  160  * unless one of the following is true:
  161  *      LK_FORCEUPGRADE is requested and some other process has already
  162  *          requested a lock upgrade (returns EBUSY).
  163  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
  164  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
  165  *      PCATCH is set in lock priority and a signal arrives (returns
  166  *          either EINTR or ERESTART if system calls is to be restarted).
  167  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
  168  * A failed lock attempt always returns a non-zero error value. No lock
  169  * is held after an error return (in particular, a failed LK_UPGRADE
  170  * or LK_FORCEUPGRADE will have released its shared access lock).
  171  */
  172 
  173 /*
  174  * Indicator that no process holds exclusive lock
  175  */
  176 #define LK_KERNTHREAD ((struct thread *)-2)
  177 #define LK_NOTHREAD ((struct thread *)-1)
  178 
  179 #ifdef _KERNEL
  180 
  181 void dumplockinfo(struct lock *lkp);
  182 struct proc;
  183 
  184 struct lock_args {
  185         struct lock     *la_lock;
  186         const char      *la_desc;
  187         int             la_flags;
  188 };
  189 
  190 void    lockinit (struct lock *, const char *wmesg, int timo, int flags);
  191 void    lockreinit (struct lock *, const char *wmesg, int timo, int flags);
  192 void    lockuninit(struct lock *);
  193 void    lock_sysinit(struct lock_args *);
  194 #ifdef DEBUG_LOCKS
  195 int     debuglockmgr (struct lock *, u_int flags,
  196                         const char *,
  197                         const char *,
  198                         int);
  199 #define lockmgr(lockp, flags) \
  200         debuglockmgr((lockp), (flags), "lockmgr", __FILE__, __LINE__)
  201 #else
  202 int     lockmgr (struct lock *, u_int flags);
  203 #endif
  204 void    lockmgr_setexclusive_interlocked(struct lock *);
  205 void    lockmgr_clrexclusive_interlocked(struct lock *);
  206 void    lockmgr_kernproc (struct lock *);
  207 void    lockmgr_printinfo (struct lock *);
  208 int     lockstatus (struct lock *, struct thread *);
  209 int     lockowned (struct lock *);
  210 int     lockcount (struct lock *);
  211 int     lockcountnb (struct lock *);
  212 
  213 #define LOCK_SYSINIT(name, lock, desc, flags)                           \
  214         static struct lock_args name##_args = {                         \
  215                 (lock),                                                 \
  216                 (desc),                                                 \
  217                 (flags)                                                 \
  218         };                                                              \
  219         SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,   \
  220             lock_sysinit, &name##_args);                                        \
  221         SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,       \
  222             lockuninit, (lock))
  223 
  224 #endif /* _KERNEL */
  225 #endif /* _KERNEL || _KERNEL_STRUCTURES */
  226 #endif /* _SYS_LOCK_H_ */

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