sys/sys/lock.h

   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. 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
  36 #ifndef _SYS_LOCK_H_
  37 #define _SYS_LOCK_H_
  38
  39 /*
  40  * A number of third party programs #include <sys/lock.h> for no good
  41  * reason.  Don't actually include anything unless we are the kernel.
  42  */
  43 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
  44
  45 #include <machine/lock.h>
  46 #ifndef _SYS_THREAD_H_
  47 #include <sys/thread.h>         /* lwkt_token */
  48 #endif
  49 #ifndef _SYS_SPINLOCK_H_
  50 #include <sys/spinlock.h>
  51 #endif
  52
  53 /*
  54  * The general lock structure.  Provides for multiple shared locks,
  55  * upgrading from shared to exclusive, and sleeping until the lock
  56  * can be gained.
  57  */
  58 struct thread;
  59
  60 struct lock {
  61         u_int   lk_flags;               /* see below */
  62         int     lk_count;               /* -shared, +exclusive */
  63         int     lk_timo;                /* maximum sleep time (for tsleep) */
  64         const char *lk_wmesg;           /* resource sleeping (for tsleep) */
  65         struct thread *lk_lockholder;   /* thread of excl lock holder */
  66 #ifdef  DEBUG_LOCKS
  67         const char *lk_filename;
  68         const char *lk_lockername;
  69         int     lk_lineno;
  70 #endif
  71 };
  72
  73 /*
  74  * Lock request types:
  75  *
  76  *   LK_SHARED
  77  *      Get one of many possible shared locks. If a process holding an
  78  *      exclusive lock requests a shared lock, the exclusive lock(s) will
  79  *      be downgraded to shared locks.
  80  *
  81  *   LK_EXCLUSIVE
  82  *      Stop further shared locks, when they are cleared, grant a pending
  83  *      upgrade if it exists, then grant an exclusive lock. Only one exclusive
  84  *      lock may exist at a time, except that a process holding an exclusive
  85  *      lock may get additional exclusive locks if it explicitly sets the
  86  *      LK_CANRECURSE flag in the lock request, or if the LK_CANRECURSE flag
  87  *      was set when the lock was initialized.
  88  *
  89  *   LK_UPGRADE
  90  *      The process must hold a shared lock that it wants to have upgraded
  91  *      to an exclusive lock. Other processes may get exclusive access to
  92  *      the resource between the time that the upgrade is requested and the
  93  *      time that it is granted.
  94  *
  95  *   LK_EXCLUPGRADE
  96  *      the process must hold a shared lock that it wants to have upgraded
  97  *      to an exclusive lock. If the request succeeds, no other processes
  98  *      will have gotten exclusive access to the resource between the time
  99  *      that the upgrade is requested and the time that it is granted.
 100  *      However, if another process has already requested an upgrade, the
 101  *      request will fail (see error returns below).
 102  *
 103  *   LK_DOWNGRADE
 104  *      The process must hold an exclusive lock that it wants to have
 105  *      downgraded to a shared lock. If the process holds multiple (recursive)
 106  *      exclusive locks, they will all be downgraded to shared locks.
 107  *
 108  *   LK_RELEASE
 109  *      Release one instance of a lock.
 110  *
 111  *   LK_CANCEL_BEG
 112  *      The current exclusive lock holder can cancel any blocked lock requests,
 113  *      or any new requests, whos callers specified LK_CANCELABLE.  They will
 114  *      receive a ENOLCK error code.  Cancel beg/end does not stack.
 115  *
 116  *      The cancel command stays in effect until the exclusive lock holder
 117  *      releases the last count on the lock or issues a LK_CANCEL_END command.
 118  *
 119  *   LK_CANCEL_END
 120  *      The current exclusive lock holder can stop canceling new requests
 121  *      whos callers specify LK_CANCELABLE.  The exclusive lock is maintained.
 122  *
 123  *      Note that the last release of the exclusive lock will also
 124  *      automatically end cancel mode.
 125  *
 126  *
 127  * ---
 128  *
 129  *   LK_EXCLOTHER - return for lockstatus().  Used when another process
 130  *      holds the lock exclusively.
 131  *
 132  * These are flags that are passed to the lockmgr routine.
 133  */
 134 #define LK_TYPE_MASK    0x0000000f      /* type of lock sought */
 135 #define LK_SHARED       0x00000001      /* shared lock */
 136 #define LK_EXCLUSIVE    0x00000002      /* exclusive lock */
 137 #define LK_UPGRADE      0x00000003      /* shared-to-exclusive upgrade */
 138 #define LK_EXCLUPGRADE  0x00000004      /* first shared-to-exclusive upgrade */
 139 #define LK_DOWNGRADE    0x00000005      /* exclusive-to-shared downgrade */
 140 #define LK_RELEASE      0x00000006      /* release any type of lock */
 141 #define LK_WAITUPGRADE  0x00000007
 142 #define LK_EXCLOTHER    0x00000008      /* other process holds lock */
 143 #define LK_CANCEL_BEG   0x00000009      /* cancel other requests */
 144 #define LK_CANCEL_END   0x0000000a      /* stop canceling other requests */
 145
 146 /*
 147  * lk_count bit fields.
 148  *
 149  * Positive count is exclusive, negative count is shared.  The count field
 150  * must be large enough to accomodate all possible threads.
 151  */
 152 #define LKC_EXREQ       0x80000000      /* waiting for exclusive lock */
 153 #define LKC_SHREQ       0x40000000      /* waiting for shared lock */
 154 #define LKC_UPREQ       0x20000000      /* waiting for upgrade */
 155 #define LKC_EXCL        0x10000000      /* exclusive (else shr or unlocked) */
 156 #define LKC_UPGRANT     0x08000000      /* upgrade granted */
 157 #define LKC_CANCEL      0x04000000      /* cancel in effect */
 158 #define LKC_MASK        0x03FFFFFF
 159
 160 /*
 161  * External lock flags.
 162  *
 163  * The first three flags may be set in lock_init to set their mode permanently,
 164  * or passed in as arguments to the lock manager.
 165  */
 166 #define LK_EXTFLG_MASK  0x07000070      /* mask of external flags */
 167 #define LK_NOWAIT       0x00000010      /* do not sleep to await lock */
 168 #define LK_SLEEPFAIL    0x00000020      /* sleep, then return failure */
 169 #define LK_CANRECURSE   0x00000040      /* allow recursive exclusive lock */
 170 #define LK_CANCELABLE   0x01000000      /* blocked caller can be canceled */
 171 #define LK_TIMELOCK     0x02000000
 172 #define LK_PCATCH       0x04000000      /* timelocked with signal catching */
 173
 174 /*
 175  * Control flags
 176  *
 177  * Non-persistent external flags.
 178  */
 179 #define LK_FAILRECLAIM  0x00010000 /* vn_lock: allowed to fail on reclaim */
 180 #define LK_RETRY        0x00020000 /* vn_lock: retry until locked */
 181 #define LK_UNUSED40000  0x00040000
 182 #define LK_UNUSED80000  0x00080000
 183
 184 /*
 185  * Lock return status.
 186  *
 187  * Successfully obtained locks return 0. Locks will always succeed
 188  * unless one of the following is true:
 189  *      LK_FORCEUPGRADE is requested and some other process has already
 190  *          requested a lock upgrade (returns EBUSY).
 191  *      LK_WAIT is set and a sleep would be required (returns EBUSY).
 192  *      LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
 193  *      PCATCH is set in lock priority and a signal arrives (returns
 194  *          either EINTR or ERESTART if system calls is to be restarted).
 195  *      Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
 196  * A failed lock attempt always returns a non-zero error value. No lock
 197  * is held after an error return (in particular, a failed LK_UPGRADE
 198  * or LK_FORCEUPGRADE will have released its shared access lock).
 199  */
 200
 201 /*
 202  * Indicator that no process holds exclusive lock
 203  */
 204 #define LK_KERNTHREAD ((struct thread *)-2)
 205 #define LK_NOTHREAD ((struct thread *)-1)
 206
 207 #ifdef _KERNEL
 208
 209 void dumplockinfo(struct lock *lkp);
 210 struct proc;
 211
 212 struct lock_args {
 213         struct lock     *la_lock;
 214         const char      *la_desc;
 215         int             la_flags;
 216 };
 217
 218 #define LOCK_INITIALIZER(wmesg, timo, flags)    \
 219 {                                               \
 220         .lk_flags = ((flags) & LK_EXTFLG_MASK), \
 221         .lk_count = 0,                          \
 222         .lk_wmesg = wmesg,                      \
 223         .lk_timo = (timo),                      \
 224         .lk_lockholder = LK_NOTHREAD            \
 225 }
 226
 227 void    lockinit (struct lock *, const char *wmesg, int timo, int flags);
 228 void    lockreinit (struct lock *, const char *wmesg, int timo, int flags);
 229 void    lockuninit(struct lock *);
 230 void    lock_sysinit(struct lock_args *);
 231 #ifdef DEBUG_LOCKS
 232 int     debuglockmgr (struct lock *, u_int flags,
 233                         const char *,
 234                         const char *,
 235                         int);
 236 #define lockmgr(lockp, flags) \
 237         debuglockmgr((lockp), (flags), "lockmgr", __FILE__, __LINE__)
 238 #else
 239 int     lockmgr (struct lock *, u_int flags);
 240 #endif
 241 void    lockmgr_setexclusive_interlocked(struct lock *);
 242 void    lockmgr_clrexclusive_interlocked(struct lock *);
 243 void    lockmgr_kernproc (struct lock *);
 244 void    lockmgr_printinfo (struct lock *);
 245 int     lockstatus (struct lock *, struct thread *);
 246 int     lockowned (struct lock *);
 247 int     lockcount (struct lock *);
 248 int     lockcountnb (struct lock *);
 249
 250 #define LOCK_SYSINIT(name, lock, desc, flags)                           \
 251         static struct lock_args name##_args = {                         \
 252                 (lock),                                                 \
 253                 (desc),                                                 \
 254                 (flags)                                                 \
 255         };                                                              \
 256         SYSINIT(name##_lock_sysinit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,   \
 257             lock_sysinit, &name##_args);                                        \
 258         SYSUNINIT(name##_lock_sysuninit, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,       \
 259             lockuninit, (lock))
 260
 261 #endif /* _KERNEL */
 262 #endif /* _KERNEL || _KERNEL_STRUCTURES */
 263 #endif /* _SYS_LOCK_H_ */