sys/kern/kern_lock.c

   1 /*
   2  * Copyright (c) 1995
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Copyright (C) 1997
   6  *      John S. Dyson.  All rights reserved.
   7  *
   8  * This code contains ideas from software contributed to Berkeley by
   9  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
  10  * System project at Carnegie-Mellon University.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. All advertising materials mentioning features or use of this software
  21  *    must display the following acknowledgement:
  22  *      This product includes software developed by the University of
  23  *      California, Berkeley and its contributors.
  24  * 4. Neither the name of the University nor the names of its contributors
  25  *    may be used to endorse or promote products derived from this software
  26  *    without specific prior written permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  38  * SUCH DAMAGE.
  39  *
  40  *      @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
  41  * $FreeBSD: src/sys/kern/kern_lock.c,v 1.31.2.3 2001/12/25 01:44:44 dillon Exp $
  42  * $DragonFly: src/sys/kern/kern_lock.c,v 1.27 2008/01/09 10:59:12 corecode Exp $
  43  */
  44
  45 #include "opt_lint.h"
  46
  47 #include <sys/param.h>
  48 #include <sys/systm.h>
  49 #include <sys/kernel.h>
  50 #include <sys/proc.h>
  51 #include <sys/lock.h>
  52 #include <sys/sysctl.h>
  53 #include <sys/spinlock.h>
  54 #include <sys/thread2.h>
  55 #include <sys/spinlock2.h>
  56
  57 /*
  58  * Locking primitives implementation.
  59  * Locks provide shared/exclusive sychronization.
  60  */
  61
  62 #ifdef DEBUG_LOCKS
  63 #define COUNT(td, x) (td)->td_locks += (x)
  64 #else
  65 #define COUNT(td, x)
  66 #endif
  67
  68 #define LOCK_WAIT_TIME 100
  69 #define LOCK_SAMPLE_WAIT 7
  70
  71 #if defined(DIAGNOSTIC)
  72 #define LOCK_INLINE
  73 #else
  74 #define LOCK_INLINE __inline
  75 #endif
  76
  77 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
  78                 LK_SHARE_NONZERO | LK_WAIT_NONZERO)
  79
  80 static int acquire(struct lock *lkp, int extflags, int wanted);
  81
  82 static LOCK_INLINE void
  83 sharelock(struct lock *lkp, int incr)
  84 {
  85         lkp->lk_flags |= LK_SHARE_NONZERO;
  86         lkp->lk_sharecount += incr;
  87 }
  88
  89 static LOCK_INLINE int
  90 shareunlock(struct lock *lkp, int decr)
  91 {
  92         int dowakeup = 0;
  93
  94         KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
  95
  96         if (lkp->lk_sharecount == decr) {
  97                 lkp->lk_flags &= ~LK_SHARE_NONZERO;
  98                 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
  99                         dowakeup = 1;
 100                 }
 101                 lkp->lk_sharecount = 0;
 102         } else {
 103                 lkp->lk_sharecount -= decr;
 104         }
 105         return(dowakeup);
 106 }
 107
 108 /*
 109  * lock acquisition helper routine.  Called with the lock's spinlock held.
 110  */
 111 static int
 112 acquire(struct lock *lkp, int extflags, int wanted)
 113 {
 114         int error;
 115
 116         if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
 117                 return EBUSY;
 118         }
 119
 120         while ((lkp->lk_flags & wanted) != 0) {
 121                 lkp->lk_flags |= LK_WAIT_NONZERO;
 122                 lkp->lk_waitcount++;
 123
 124                 /*
 125                  * Atomic spinlock release/sleep/reacquire.
 126                  */
 127                 error = ssleep(lkp, &lkp->lk_spinlock,
 128                                ((extflags & LK_PCATCH) ? PCATCH : 0),
 129                                lkp->lk_wmesg,
 130                                ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
 131                 if (lkp->lk_waitcount == 1) {
 132                         lkp->lk_flags &= ~LK_WAIT_NONZERO;
 133                         lkp->lk_waitcount = 0;
 134                 } else {
 135                         lkp->lk_waitcount--;
 136                 }
 137                 if (error)
 138                         return error;
 139                 if (extflags & LK_SLEEPFAIL)
 140                         return ENOLCK;
 141         }
 142         return 0;
 143 }
 144
 145 /*
 146  * Set, change, or release a lock.
 147  *
 148  * Shared requests increment the shared count. Exclusive requests set the
 149  * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
 150  * accepted shared locks and shared-to-exclusive upgrades to go away.
 151  *
 152  * A spinlock is held for most of the procedure.  We must not do anything
 153  * fancy while holding the spinlock.
 154  */
 155 int
 156 #ifndef DEBUG_LOCKS
 157 lockmgr(struct lock *lkp, u_int flags)
 158 #else
 159 debuglockmgr(struct lock *lkp, u_int flags,
 160              const char *name, const char *file, int line)
 161 #endif
 162 {
 163         thread_t td;
 164         int error;
 165         int extflags;
 166         int dowakeup;
 167 #ifdef DEBUG_LOCKS
 168         int i;
 169 #endif
 170
 171         error = 0;
 172         dowakeup = 0;
 173
 174         if (mycpu->gd_intr_nesting_level &&
 175             (flags & LK_NOWAIT) == 0 &&
 176             (flags & LK_TYPE_MASK) != LK_RELEASE &&
 177             panic_cpu_gd != mycpu
 178         ) {
 179
 180 #ifndef DEBUG_LOCKS
 181                 panic("lockmgr %s from %p: called from interrupt, ipi, "
 182                       "or hard code section",
 183                       lkp->lk_wmesg, ((int **)&lkp)[-1]);
 184 #else
 185                 panic("lockmgr %s from %s:%d: called from interrupt, ipi, "
 186                       "or hard code section",
 187                       lkp->lk_wmesg, file, line);
 188 #endif
 189         }
 190
 191 #ifdef DEBUG_LOCKS
 192         if (mycpu->gd_spinlocks_wr &&
 193             ((flags & LK_NOWAIT) == 0)
 194         ) {
 195                 panic("lockmgr %s from %s:%d: called with %d spinlocks held",
 196                       lkp->lk_wmesg, file, line, mycpu->gd_spinlocks_wr);
 197         }
 198 #endif
 199
 200         spin_lock(&lkp->lk_spinlock);
 201
 202         extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
 203         td = curthread;
 204
 205         switch (flags & LK_TYPE_MASK) {
 206         case LK_SHARED:
 207                 /*
 208                  * If we are not the exclusive lock holder, we have to block
 209                  * while there is an exclusive lock holder or while an
 210                  * exclusive lock request or upgrade request is in progress.
 211                  *
 212                  * However, if TDF_DEADLKTREAT is set, we override exclusive
 213                  * lock requests or upgrade requests ( but not the exclusive
 214                  * lock itself ).
 215                  */
 216                 if (lkp->lk_lockholder != td) {
 217                         if (td->td_flags & TDF_DEADLKTREAT) {
 218                                 error = acquire(
 219                                             lkp,
 220                                             extflags,
 221                                             LK_HAVE_EXCL
 222                                         );
 223                         } else {
 224                                 error = acquire(
 225                                             lkp,
 226                                             extflags,
 227                                             LK_HAVE_EXCL | LK_WANT_EXCL |
 228                                              LK_WANT_UPGRADE
 229                                         );
 230                         }
 231                         if (error)
 232                                 break;
 233                         sharelock(lkp, 1);
 234                         COUNT(td, 1);
 235                         break;
 236                 }
 237
 238                 /*
 239                  * If we already hold an exclusive lock we bump the
 240                  * exclusive count instead of downgrading to a shared
 241                  * lock.
 242                  *
 243                  * WARNING!  The old FreeBSD behavior was to downgrade,
 244                  *           but this creates a problem when recursions
 245                  *           return to the caller and the caller expects
 246                  *           its original exclusive lock to remain exclusively
 247                  *           locked.
 248                  */
 249                 if (extflags & LK_CANRECURSE) {
 250                         lkp->lk_exclusivecount++;
 251                         COUNT(td, 1);
 252                         break;
 253                 }
 254                 if (extflags & LK_NOWAIT) {
 255                         error = EBUSY;
 256                         break;
 257                 }
 258                 spin_unlock(&lkp->lk_spinlock);
 259                 panic("lockmgr: locking against myself");
 260 #if 0
 261                 /*
 262                  * old code queued a shared lock request fell into
 263                  * a downgrade.
 264                  */
 265                 sharelock(lkp, 1);
 266                 COUNT(td, 1);
 267                 /* fall into downgrade */
 268 #endif
 269
 270         case LK_DOWNGRADE:
 271                 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0) {
 272                         spin_unlock(&lkp->lk_spinlock);
 273                         panic("lockmgr: not holding exclusive lock");
 274                 }
 275
 276 #ifdef DEBUG_LOCKS
 277                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 278                         if (td->td_lockmgr_stack[i] == lkp &&
 279                             td->td_lockmgr_stack_id[i] > 0
 280                         ) {
 281                                 td->td_lockmgr_stack_id[i]--;
 282                                 break;
 283                         }
 284                 }
 285 #endif
 286
 287                 sharelock(lkp, lkp->lk_exclusivecount);
 288                 lkp->lk_exclusivecount = 0;
 289                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 290                 lkp->lk_lockholder = LK_NOTHREAD;
 291                 if (lkp->lk_waitcount)
 292                         dowakeup = 1;
 293                 break;
 294
 295         case LK_EXCLUPGRADE:
 296                 /*
 297                  * If another process is ahead of us to get an upgrade,
 298                  * then we want to fail rather than have an intervening
 299                  * exclusive access.
 300                  */
 301                 if (lkp->lk_flags & LK_WANT_UPGRADE) {
 302                         dowakeup = shareunlock(lkp, 1);
 303                         COUNT(td, -1);
 304                         error = EBUSY;
 305                         break;
 306                 }
 307                 /* fall into normal upgrade */
 308
 309         case LK_UPGRADE:
 310                 /*
 311                  * Upgrade a shared lock to an exclusive one. If another
 312                  * shared lock has already requested an upgrade to an
 313                  * exclusive lock, our shared lock is released and an
 314                  * exclusive lock is requested (which will be granted
 315                  * after the upgrade). If we return an error, the file
 316                  * will always be unlocked.
 317                  */
 318                 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0)) {
 319                         spin_unlock(&lkp->lk_spinlock);
 320                         panic("lockmgr: upgrade exclusive lock");
 321                 }
 322                 dowakeup += shareunlock(lkp, 1);
 323                 COUNT(td, -1);
 324                 /*
 325                  * If we are just polling, check to see if we will block.
 326                  */
 327                 if ((extflags & LK_NOWAIT) &&
 328                     ((lkp->lk_flags & LK_WANT_UPGRADE) ||
 329                      lkp->lk_sharecount > 1)) {
 330                         error = EBUSY;
 331                         break;
 332                 }
 333                 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
 334                         /*
 335                          * We are first shared lock to request an upgrade, so
 336                          * request upgrade and wait for the shared count to
 337                          * drop to zero, then take exclusive lock.
 338                          *
 339                          * Although I don't think this can occur for
 340                          * robustness we also wait for any exclusive locks
 341                          * to be released.  LK_WANT_UPGRADE is supposed to
 342                          * prevent new exclusive locks but might not in the
 343                          * future.
 344                          */
 345                         lkp->lk_flags |= LK_WANT_UPGRADE;
 346                         error = acquire(lkp, extflags,
 347                                         LK_HAVE_EXCL | LK_SHARE_NONZERO);
 348                         lkp->lk_flags &= ~LK_WANT_UPGRADE;
 349
 350                         if (error)
 351                                 break;
 352                         lkp->lk_flags |= LK_HAVE_EXCL;
 353                         lkp->lk_lockholder = td;
 354                         if (lkp->lk_exclusivecount != 0) {
 355                                 spin_unlock(&lkp->lk_spinlock);
 356                                 panic("lockmgr(1): non-zero exclusive count");
 357                         }
 358                         lkp->lk_exclusivecount = 1;
 359 #if defined(DEBUG_LOCKS)
 360                         lkp->lk_filename = file;
 361                         lkp->lk_lineno = line;
 362                         lkp->lk_lockername = name;
 363
 364                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 365                                 /*
 366                                  * Recursive lockmgr path
 367                                  */
 368                                 if (td->td_lockmgr_stack[i] == lkp &&
 369                                     td->td_lockmgr_stack_id[i] != 0
 370                                 ) {
 371                                         td->td_lockmgr_stack_id[i]++;
 372                                         goto lkmatch2;
 373                                 }
 374                        }
 375
 376                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 377                                 /*
 378                                  * Use new lockmgr tracking slot
 379                                  */
 380                                 if (td->td_lockmgr_stack_id[i] == 0) {
 381                                         td->td_lockmgr_stack_id[i]++;
 382                                         td->td_lockmgr_stack[i] = lkp;
 383                                         break;
 384                                 }
 385                         }
 386 lkmatch2:
 387                         ;
 388 #endif
 389                         COUNT(td, 1);
 390                         break;
 391                 }
 392                 /*
 393                  * Someone else has requested upgrade. Release our shared
 394                  * lock, awaken upgrade requestor if we are the last shared
 395                  * lock, then request an exclusive lock.
 396                  */
 397                 if ((lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
 398                     LK_WAIT_NONZERO) {
 399                         ++dowakeup;
 400                 }
 401                 /* fall into exclusive request */
 402
 403         case LK_EXCLUSIVE:
 404                 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) {
 405                         /*
 406                          *      Recursive lock.
 407                          */
 408                         if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) {
 409                                 spin_unlock(&lkp->lk_spinlock);
 410                                 panic("lockmgr: locking against myself");
 411                         }
 412                         if ((extflags & LK_CANRECURSE) != 0) {
 413                                 lkp->lk_exclusivecount++;
 414                                 COUNT(td, 1);
 415                                 break;
 416                         }
 417                 }
 418                 /*
 419                  * If we are just polling, check to see if we will sleep.
 420                  */
 421                 if ((extflags & LK_NOWAIT) &&
 422                     (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL |
 423                                       LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
 424                         error = EBUSY;
 425                         break;
 426                 }
 427                 /*
 428                  * Wait for exclusive lock holders to release and try to
 429                  * acquire the want_exclusive flag.
 430                  */
 431                 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
 432                 if (error)
 433                         break;
 434                 lkp->lk_flags |= LK_WANT_EXCL;
 435
 436                 /*
 437                  * Wait for shared locks and upgrades to finish.  We can lose
 438                  * the race against a successful shared lock upgrade in which
 439                  * case LK_HAVE_EXCL will get set regardless of our
 440                  * acquisition of LK_WANT_EXCL, so we have to acquire
 441                  * LK_HAVE_EXCL here as well.
 442                  */
 443                 error = acquire(lkp, extflags, LK_HAVE_EXCL |
 444                                                LK_WANT_UPGRADE |
 445                                                LK_SHARE_NONZERO);
 446                 lkp->lk_flags &= ~LK_WANT_EXCL;
 447                 if (error)
 448                         break;
 449                 lkp->lk_flags |= LK_HAVE_EXCL;
 450                 lkp->lk_lockholder = td;
 451                 if (lkp->lk_exclusivecount != 0) {
 452                         spin_unlock(&lkp->lk_spinlock);
 453                         panic("lockmgr(2): non-zero exclusive count");
 454                 }
 455                 lkp->lk_exclusivecount = 1;
 456 #if defined(DEBUG_LOCKS)
 457                 lkp->lk_filename = file;
 458                 lkp->lk_lineno = line;
 459                 lkp->lk_lockername = name;
 460
 461                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 462                         /*
 463                          * Recursive lockmgr path
 464                          */
 465                         if (td->td_lockmgr_stack[i] == lkp &&
 466                             td->td_lockmgr_stack_id[i] != 0
 467                         ) {
 468                                 td->td_lockmgr_stack_id[i]++;
 469                                 goto lkmatch1;
 470                         }
 471                 }
 472
 473                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 474                         /*
 475                          * Use new lockmgr tracking slot
 476                          */
 477                         if (td->td_lockmgr_stack_id[i] == 0) {
 478                                 td->td_lockmgr_stack_id[i]++;
 479                                 td->td_lockmgr_stack[i] = lkp;
 480                                 break;
 481                         }
 482                 }
 483 lkmatch1:
 484                 ;
 485 #endif
 486                 COUNT(td, 1);
 487                 break;
 488
 489         case LK_RELEASE:
 490                 if (lkp->lk_exclusivecount != 0) {
 491                         if (lkp->lk_lockholder != td &&
 492                             lkp->lk_lockholder != LK_KERNTHREAD) {
 493                                 spin_unlock(&lkp->lk_spinlock);
 494                                 panic("lockmgr: pid %d, not %s thr %p/%p unlocking",
 495                                     (td->td_proc ? td->td_proc->p_pid : -1),
 496                                     "exclusive lock holder",
 497                                     td, lkp->lk_lockholder);
 498                         }
 499                         if (lkp->lk_lockholder != LK_KERNTHREAD) {
 500                                 COUNT(td, -1);
 501                         }
 502                         if (lkp->lk_exclusivecount == 1) {
 503                                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 504                                 lkp->lk_lockholder = LK_NOTHREAD;
 505                                 lkp->lk_exclusivecount = 0;
 506                         } else {
 507                                 lkp->lk_exclusivecount--;
 508                         }
 509 #ifdef DEBUG_LOCKS
 510                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 511                                 if (td->td_lockmgr_stack[i] == lkp &&
 512                                     td->td_lockmgr_stack_id[i] > 0
 513                                 ) {
 514                                         td->td_lockmgr_stack_id[i]--;
 515                                         lkp->lk_filename = file;
 516                                         lkp->lk_lineno = line;
 517                                         break;
 518                                 }
 519                         }
 520 #endif
 521                 } else if (lkp->lk_flags & LK_SHARE_NONZERO) {
 522                         dowakeup += shareunlock(lkp, 1);
 523                         COUNT(td, -1);
 524                 } else {
 525                         panic("lockmgr: LK_RELEASE: no lock held");
 526                 }
 527                 if (lkp->lk_flags & LK_WAIT_NONZERO)
 528                         ++dowakeup;
 529                 break;
 530
 531         default:
 532                 spin_unlock(&lkp->lk_spinlock);
 533                 panic("lockmgr: unknown locktype request %d",
 534                     flags & LK_TYPE_MASK);
 535                 /* NOTREACHED */
 536         }
 537         spin_unlock(&lkp->lk_spinlock);
 538         if (dowakeup)
 539                 wakeup(lkp);
 540         return (error);
 541 }
 542
 543 void
 544 lockmgr_kernproc(struct lock *lp)
 545 {
 546         struct thread *td __debugvar = curthread;
 547
 548         if (lp->lk_lockholder != LK_KERNTHREAD) {
 549                 KASSERT(lp->lk_lockholder == td,
 550                     ("lockmgr_kernproc: lock not owned by curthread %p", td));
 551                 COUNT(td, -1);
 552                 lp->lk_lockholder = LK_KERNTHREAD;
 553         }
 554 }
 555
 556 #if 0
 557 /*
 558  * Set the lock to be exclusively held.  The caller is holding the lock's
 559  * spinlock and the spinlock remains held on return.  A panic will occur
 560  * if the lock cannot be set to exclusive.
 561  *
 562  * XXX not only unused but these functions also break EXCLUPGRADE's
 563  * atomicy.
 564  */
 565 void
 566 lockmgr_setexclusive_interlocked(struct lock *lkp)
 567 {
 568         thread_t td = curthread;
 569
 570         KKASSERT((lkp->lk_flags & (LK_HAVE_EXCL|LK_SHARE_NONZERO)) == 0);
 571         KKASSERT(lkp->lk_exclusivecount == 0);
 572         lkp->lk_flags |= LK_HAVE_EXCL;
 573         lkp->lk_lockholder = td;
 574         lkp->lk_exclusivecount = 1;
 575         COUNT(td, 1);
 576 }
 577
 578 /*
 579  * Clear the caller's exclusive lock.  The caller is holding the lock's
 580  * spinlock.  THIS FUNCTION WILL UNLOCK THE SPINLOCK.
 581  *
 582  * A panic will occur if the caller does not hold the lock.
 583  */
 584 void
 585 lockmgr_clrexclusive_interlocked(struct lock *lkp)
 586 {
 587         thread_t td __debugvar = curthread;
 588         int dowakeup = 0;
 589
 590         KKASSERT((lkp->lk_flags & LK_HAVE_EXCL) && lkp->lk_exclusivecount == 1
 591                  && lkp->lk_lockholder == td);
 592         lkp->lk_lockholder = LK_NOTHREAD;
 593         lkp->lk_flags &= ~LK_HAVE_EXCL;
 594         lkp->lk_exclusivecount = 0;
 595         if (lkp->lk_flags & LK_WAIT_NONZERO)
 596                 dowakeup = 1;
 597         COUNT(td, -1);
 598         spin_unlock(&lkp->lk_spinlock);
 599         if (dowakeup)
 600                 wakeup((void *)lkp);
 601 }
 602
 603 #endif
 604
 605 /*
 606  * Initialize a lock; required before use.
 607  */
 608 void
 609 lockinit(struct lock *lkp, const char *wmesg, int timo, int flags)
 610 {
 611         spin_init(&lkp->lk_spinlock);
 612         lkp->lk_flags = (flags & LK_EXTFLG_MASK);
 613         lkp->lk_sharecount = 0;
 614         lkp->lk_waitcount = 0;
 615         lkp->lk_exclusivecount = 0;
 616         lkp->lk_wmesg = wmesg;
 617         lkp->lk_timo = timo;
 618         lkp->lk_lockholder = LK_NOTHREAD;
 619 }
 620
 621 /*
 622  * Reinitialize a lock that is being reused for a different purpose, but
 623  * which may have pending (blocked) threads sitting on it.  The caller
 624  * must already hold the interlock.
 625  */
 626 void
 627 lockreinit(struct lock *lkp, const char *wmesg, int timo, int flags)
 628 {
 629         spin_lock(&lkp->lk_spinlock);
 630         lkp->lk_flags = (lkp->lk_flags & ~LK_EXTFLG_MASK) |
 631                         (flags & LK_EXTFLG_MASK);
 632         lkp->lk_wmesg = wmesg;
 633         lkp->lk_timo = timo;
 634         spin_unlock(&lkp->lk_spinlock);
 635 }
 636
 637 /*
 638  * Requires that the caller is the exclusive owner of this lock.
 639  */
 640 void
 641 lockuninit(struct lock *l)
 642 {
 643         /*
 644          * At this point we should have removed all the references to this lock
 645          * so there can't be anyone waiting on it.
 646          */
 647         KKASSERT(l->lk_waitcount == 0);
 648
 649         spin_uninit(&l->lk_spinlock);
 650 }
 651
 652 /*
 653  * Determine the status of a lock.
 654  */
 655 int
 656 lockstatus(struct lock *lkp, struct thread *td)
 657 {
 658         int lock_type = 0;
 659
 660         spin_lock(&lkp->lk_spinlock);
 661         if (lkp->lk_exclusivecount != 0) {
 662                 if (td == NULL || lkp->lk_lockholder == td)
 663                         lock_type = LK_EXCLUSIVE;
 664                 else
 665                         lock_type = LK_EXCLOTHER;
 666         } else if (lkp->lk_sharecount != 0) {
 667                 lock_type = LK_SHARED;
 668         }
 669         spin_unlock(&lkp->lk_spinlock);
 670         return (lock_type);
 671 }
 672
 673 /*
 674  * Return non-zero if the caller owns the lock shared or exclusive.
 675  * We can only guess re: shared locks.
 676  */
 677 int
 678 lockowned(struct lock *lkp)
 679 {
 680         thread_t td = curthread;
 681
 682         if (lkp->lk_exclusivecount)
 683                 return(lkp->lk_lockholder == td);
 684         return(lkp->lk_sharecount != 0);
 685 }
 686
 687 /*
 688  * Determine the number of holders of a lock.
 689  *
 690  * The non-blocking version can usually be used for assertions.
 691  */
 692 int
 693 lockcount(struct lock *lkp)
 694 {
 695         int count;
 696
 697         spin_lock(&lkp->lk_spinlock);
 698         count = lkp->lk_exclusivecount + lkp->lk_sharecount;
 699         spin_unlock(&lkp->lk_spinlock);
 700         return (count);
 701 }
 702
 703 int
 704 lockcountnb(struct lock *lkp)
 705 {
 706         return (lkp->lk_exclusivecount + lkp->lk_sharecount);
 707 }
 708
 709 /*
 710  * Print out information about state of a lock. Used by VOP_PRINT
 711  * routines to display status about contained locks.
 712  */
 713 void
 714 lockmgr_printinfo(struct lock *lkp)
 715 {
 716         struct thread *td = lkp->lk_lockholder;
 717         struct proc *p;
 718
 719         if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
 720                 p = td->td_proc;
 721         else
 722                 p = NULL;
 723
 724         if (lkp->lk_sharecount)
 725                 kprintf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
 726                     lkp->lk_sharecount);
 727         else if (lkp->lk_flags & LK_HAVE_EXCL)
 728                 kprintf(" lock type %s: EXCL (count %d) by td %p pid %d",
 729                     lkp->lk_wmesg, lkp->lk_exclusivecount, td,
 730                     p ? p->p_pid : -99);
 731         if (lkp->lk_waitcount > 0)
 732                 kprintf(" with %d pending", lkp->lk_waitcount);
 733 }
 734
 735 void
 736 lock_sysinit(struct lock_args *arg)
 737 {
 738         lockinit(arg->la_lock, arg->la_desc, 0, arg->la_flags);
 739 }