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 && ((flags & LK_NOWAIT) == 0)) {
 193                 panic("lockmgr %s from %s:%d: called with %d spinlocks held",
 194                       lkp->lk_wmesg, file, line, mycpu->gd_spinlocks);
 195         }
 196 #endif
 197
 198         spin_lock(&lkp->lk_spinlock);
 199
 200         extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
 201         td = curthread;
 202
 203         switch (flags & LK_TYPE_MASK) {
 204         case LK_SHARED:
 205                 /*
 206                  * If we are not the exclusive lock holder, we have to block
 207                  * while there is an exclusive lock holder or while an
 208                  * exclusive lock request or upgrade request is in progress.
 209                  *
 210                  * However, if TDF_DEADLKTREAT is set, we override exclusive
 211                  * lock requests or upgrade requests ( but not the exclusive
 212                  * lock itself ).
 213                  */
 214                 if (lkp->lk_lockholder != td) {
 215                         if (td->td_flags & TDF_DEADLKTREAT) {
 216                                 error = acquire(
 217                                             lkp,
 218                                             extflags,
 219                                             LK_HAVE_EXCL
 220                                         );
 221                         } else {
 222                                 error = acquire(
 223                                             lkp,
 224                                             extflags,
 225                                             LK_HAVE_EXCL | LK_WANT_EXCL |
 226                                              LK_WANT_UPGRADE
 227                                         );
 228                         }
 229                         if (error)
 230                                 break;
 231                         sharelock(lkp, 1);
 232                         COUNT(td, 1);
 233                         break;
 234                 }
 235
 236                 /*
 237                  * If we already hold an exclusive lock we bump the
 238                  * exclusive count instead of downgrading to a shared
 239                  * lock.
 240                  *
 241                  * WARNING!  The old FreeBSD behavior was to downgrade,
 242                  *           but this creates a problem when recursions
 243                  *           return to the caller and the caller expects
 244                  *           its original exclusive lock to remain exclusively
 245                  *           locked.
 246                  */
 247                 if (extflags & LK_CANRECURSE) {
 248                         lkp->lk_exclusivecount++;
 249                         COUNT(td, 1);
 250                         break;
 251                 }
 252                 if (extflags & LK_NOWAIT) {
 253                         error = EBUSY;
 254                         break;
 255                 }
 256                 spin_unlock(&lkp->lk_spinlock);
 257                 panic("lockmgr: locking against myself");
 258 #if 0
 259                 /*
 260                  * old code queued a shared lock request fell into
 261                  * a downgrade.
 262                  */
 263                 sharelock(lkp, 1);
 264                 COUNT(td, 1);
 265                 /* fall into downgrade */
 266 #endif
 267
 268         case LK_DOWNGRADE:
 269                 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0) {
 270                         spin_unlock(&lkp->lk_spinlock);
 271                         panic("lockmgr: not holding exclusive lock");
 272                 }
 273
 274 #ifdef DEBUG_LOCKS
 275                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 276                         if (td->td_lockmgr_stack[i] == lkp &&
 277                             td->td_lockmgr_stack_id[i] > 0
 278                         ) {
 279                                 td->td_lockmgr_stack_id[i]--;
 280                                 break;
 281                         }
 282                 }
 283 #endif
 284
 285                 sharelock(lkp, lkp->lk_exclusivecount);
 286                 lkp->lk_exclusivecount = 0;
 287                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 288                 lkp->lk_lockholder = LK_NOTHREAD;
 289                 if (lkp->lk_waitcount)
 290                         dowakeup = 1;
 291                 break;
 292
 293         case LK_EXCLUPGRADE:
 294                 /*
 295                  * If another process is ahead of us to get an upgrade,
 296                  * then we want to fail rather than have an intervening
 297                  * exclusive access.
 298                  */
 299                 if (lkp->lk_flags & LK_WANT_UPGRADE) {
 300                         dowakeup = shareunlock(lkp, 1);
 301                         COUNT(td, -1);
 302                         error = EBUSY;
 303                         break;
 304                 }
 305                 /* fall into normal upgrade */
 306
 307         case LK_UPGRADE:
 308                 /*
 309                  * Upgrade a shared lock to an exclusive one. If another
 310                  * shared lock has already requested an upgrade to an
 311                  * exclusive lock, our shared lock is released and an
 312                  * exclusive lock is requested (which will be granted
 313                  * after the upgrade). If we return an error, the file
 314                  * will always be unlocked.
 315                  */
 316                 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0)) {
 317                         spin_unlock(&lkp->lk_spinlock);
 318                         panic("lockmgr: upgrade exclusive lock");
 319                 }
 320                 dowakeup += shareunlock(lkp, 1);
 321                 COUNT(td, -1);
 322                 /*
 323                  * If we are just polling, check to see if we will block.
 324                  */
 325                 if ((extflags & LK_NOWAIT) &&
 326                     ((lkp->lk_flags & LK_WANT_UPGRADE) ||
 327                      lkp->lk_sharecount > 1)) {
 328                         error = EBUSY;
 329                         break;
 330                 }
 331                 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
 332                         /*
 333                          * We are first shared lock to request an upgrade, so
 334                          * request upgrade and wait for the shared count to
 335                          * drop to zero, then take exclusive lock.
 336                          *
 337                          * Although I don't think this can occur for
 338                          * robustness we also wait for any exclusive locks
 339                          * to be released.  LK_WANT_UPGRADE is supposed to
 340                          * prevent new exclusive locks but might not in the
 341                          * future.
 342                          */
 343                         lkp->lk_flags |= LK_WANT_UPGRADE;
 344                         error = acquire(lkp, extflags,
 345                                         LK_HAVE_EXCL | LK_SHARE_NONZERO);
 346                         lkp->lk_flags &= ~LK_WANT_UPGRADE;
 347
 348                         if (error)
 349                                 break;
 350                         lkp->lk_flags |= LK_HAVE_EXCL;
 351                         lkp->lk_lockholder = td;
 352                         if (lkp->lk_exclusivecount != 0) {
 353                                 spin_unlock(&lkp->lk_spinlock);
 354                                 panic("lockmgr(1): non-zero exclusive count");
 355                         }
 356                         lkp->lk_exclusivecount = 1;
 357 #if defined(DEBUG_LOCKS)
 358                         lkp->lk_filename = file;
 359                         lkp->lk_lineno = line;
 360                         lkp->lk_lockername = name;
 361
 362                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 363                                 /*
 364                                  * Recursive lockmgr path
 365                                  */
 366                                 if (td->td_lockmgr_stack[i] == lkp &&
 367                                     td->td_lockmgr_stack_id[i] != 0
 368                                 ) {
 369                                         td->td_lockmgr_stack_id[i]++;
 370                                         goto lkmatch2;
 371                                 }
 372                        }
 373
 374                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 375                                 /*
 376                                  * Use new lockmgr tracking slot
 377                                  */
 378                                 if (td->td_lockmgr_stack_id[i] == 0) {
 379                                         td->td_lockmgr_stack_id[i]++;
 380                                         td->td_lockmgr_stack[i] = lkp;
 381                                         break;
 382                                 }
 383                         }
 384 lkmatch2:
 385                         ;
 386 #endif
 387                         COUNT(td, 1);
 388                         break;
 389                 }
 390                 /*
 391                  * Someone else has requested upgrade. Release our shared
 392                  * lock, awaken upgrade requestor if we are the last shared
 393                  * lock, then request an exclusive lock.
 394                  */
 395                 if ((lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
 396                     LK_WAIT_NONZERO) {
 397                         ++dowakeup;
 398                 }
 399                 /* fall into exclusive request */
 400
 401         case LK_EXCLUSIVE:
 402                 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) {
 403                         /*
 404                          *      Recursive lock.
 405                          */
 406                         if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) {
 407                                 spin_unlock(&lkp->lk_spinlock);
 408                                 panic("lockmgr: locking against myself");
 409                         }
 410                         if ((extflags & LK_CANRECURSE) != 0) {
 411                                 lkp->lk_exclusivecount++;
 412                                 COUNT(td, 1);
 413                                 break;
 414                         }
 415                 }
 416                 /*
 417                  * If we are just polling, check to see if we will sleep.
 418                  */
 419                 if ((extflags & LK_NOWAIT) &&
 420                     (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL |
 421                                       LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
 422                         error = EBUSY;
 423                         break;
 424                 }
 425                 /*
 426                  * Wait for exclusive lock holders to release and try to
 427                  * acquire the want_exclusive flag.
 428                  */
 429                 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
 430                 if (error)
 431                         break;
 432                 lkp->lk_flags |= LK_WANT_EXCL;
 433
 434                 /*
 435                  * Wait for shared locks and upgrades to finish.  We can lose
 436                  * the race against a successful shared lock upgrade in which
 437                  * case LK_HAVE_EXCL will get set regardless of our
 438                  * acquisition of LK_WANT_EXCL, so we have to acquire
 439                  * LK_HAVE_EXCL here as well.
 440                  */
 441                 error = acquire(lkp, extflags, LK_HAVE_EXCL |
 442                                                LK_WANT_UPGRADE |
 443                                                LK_SHARE_NONZERO);
 444                 lkp->lk_flags &= ~LK_WANT_EXCL;
 445                 if (error)
 446                         break;
 447                 lkp->lk_flags |= LK_HAVE_EXCL;
 448                 lkp->lk_lockholder = td;
 449                 if (lkp->lk_exclusivecount != 0) {
 450                         spin_unlock(&lkp->lk_spinlock);
 451                         panic("lockmgr(2): non-zero exclusive count");
 452                 }
 453                 lkp->lk_exclusivecount = 1;
 454 #if defined(DEBUG_LOCKS)
 455                 lkp->lk_filename = file;
 456                 lkp->lk_lineno = line;
 457                 lkp->lk_lockername = name;
 458
 459                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 460                         /*
 461                          * Recursive lockmgr path
 462                          */
 463                         if (td->td_lockmgr_stack[i] == lkp &&
 464                             td->td_lockmgr_stack_id[i] != 0
 465                         ) {
 466                                 td->td_lockmgr_stack_id[i]++;
 467                                 goto lkmatch1;
 468                         }
 469                 }
 470
 471                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 472                         /*
 473                          * Use new lockmgr tracking slot
 474                          */
 475                         if (td->td_lockmgr_stack_id[i] == 0) {
 476                                 td->td_lockmgr_stack_id[i]++;
 477                                 td->td_lockmgr_stack[i] = lkp;
 478                                 break;
 479                         }
 480                 }
 481 lkmatch1:
 482                 ;
 483 #endif
 484                 COUNT(td, 1);
 485                 break;
 486
 487         case LK_RELEASE:
 488                 if (lkp->lk_exclusivecount != 0) {
 489                         if (lkp->lk_lockholder != td &&
 490                             lkp->lk_lockholder != LK_KERNTHREAD) {
 491                                 spin_unlock(&lkp->lk_spinlock);
 492                                 panic("lockmgr: pid %d, not %s thr %p/%p unlocking",
 493                                     (td->td_proc ? td->td_proc->p_pid : -1),
 494                                     "exclusive lock holder",
 495                                     td, lkp->lk_lockholder);
 496                         }
 497                         if (lkp->lk_lockholder != LK_KERNTHREAD) {
 498                                 COUNT(td, -1);
 499                         }
 500                         if (lkp->lk_exclusivecount == 1) {
 501                                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 502                                 lkp->lk_lockholder = LK_NOTHREAD;
 503                                 lkp->lk_exclusivecount = 0;
 504                         } else {
 505                                 lkp->lk_exclusivecount--;
 506                         }
 507 #ifdef DEBUG_LOCKS
 508                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 509                                 if (td->td_lockmgr_stack[i] == lkp &&
 510                                     td->td_lockmgr_stack_id[i] > 0
 511                                 ) {
 512                                         td->td_lockmgr_stack_id[i]--;
 513                                         lkp->lk_filename = file;
 514                                         lkp->lk_lineno = line;
 515                                         break;
 516                                 }
 517                         }
 518 #endif
 519                 } else if (lkp->lk_flags & LK_SHARE_NONZERO) {
 520                         dowakeup += shareunlock(lkp, 1);
 521                         COUNT(td, -1);
 522                 } else {
 523                         panic("lockmgr: LK_RELEASE: no lock held");
 524                 }
 525                 if (lkp->lk_flags & LK_WAIT_NONZERO)
 526                         ++dowakeup;
 527                 break;
 528
 529         default:
 530                 spin_unlock(&lkp->lk_spinlock);
 531                 panic("lockmgr: unknown locktype request %d",
 532                     flags & LK_TYPE_MASK);
 533                 /* NOTREACHED */
 534         }
 535         spin_unlock(&lkp->lk_spinlock);
 536         if (dowakeup)
 537                 wakeup(lkp);
 538         return (error);
 539 }
 540
 541 void
 542 lockmgr_kernproc(struct lock *lp)
 543 {
 544         struct thread *td __debugvar = curthread;
 545
 546         if (lp->lk_lockholder != LK_KERNTHREAD) {
 547                 KASSERT(lp->lk_lockholder == td,
 548                     ("lockmgr_kernproc: lock not owned by curthread %p", td));
 549                 COUNT(td, -1);
 550                 lp->lk_lockholder = LK_KERNTHREAD;
 551         }
 552 }
 553
 554 #if 0
 555 /*
 556  * Set the lock to be exclusively held.  The caller is holding the lock's
 557  * spinlock and the spinlock remains held on return.  A panic will occur
 558  * if the lock cannot be set to exclusive.
 559  *
 560  * XXX not only unused but these functions also break EXCLUPGRADE's
 561  * atomicy.
 562  */
 563 void
 564 lockmgr_setexclusive_interlocked(struct lock *lkp)
 565 {
 566         thread_t td = curthread;
 567
 568         KKASSERT((lkp->lk_flags & (LK_HAVE_EXCL|LK_SHARE_NONZERO)) == 0);
 569         KKASSERT(lkp->lk_exclusivecount == 0);
 570         lkp->lk_flags |= LK_HAVE_EXCL;
 571         lkp->lk_lockholder = td;
 572         lkp->lk_exclusivecount = 1;
 573         COUNT(td, 1);
 574 }
 575
 576 /*
 577  * Clear the caller's exclusive lock.  The caller is holding the lock's
 578  * spinlock.  THIS FUNCTION WILL UNLOCK THE SPINLOCK.
 579  *
 580  * A panic will occur if the caller does not hold the lock.
 581  */
 582 void
 583 lockmgr_clrexclusive_interlocked(struct lock *lkp)
 584 {
 585         thread_t td __debugvar = curthread;
 586         int dowakeup = 0;
 587
 588         KKASSERT((lkp->lk_flags & LK_HAVE_EXCL) && lkp->lk_exclusivecount == 1
 589                  && lkp->lk_lockholder == td);
 590         lkp->lk_lockholder = LK_NOTHREAD;
 591         lkp->lk_flags &= ~LK_HAVE_EXCL;
 592         lkp->lk_exclusivecount = 0;
 593         if (lkp->lk_flags & LK_WAIT_NONZERO)
 594                 dowakeup = 1;
 595         COUNT(td, -1);
 596         spin_unlock(&lkp->lk_spinlock);
 597         if (dowakeup)
 598                 wakeup((void *)lkp);
 599 }
 600
 601 #endif
 602
 603 /*
 604  * Initialize a lock; required before use.
 605  */
 606 void
 607 lockinit(struct lock *lkp, const char *wmesg, int timo, int flags)
 608 {
 609         spin_init(&lkp->lk_spinlock);
 610         lkp->lk_flags = (flags & LK_EXTFLG_MASK);
 611         lkp->lk_sharecount = 0;
 612         lkp->lk_waitcount = 0;
 613         lkp->lk_exclusivecount = 0;
 614         lkp->lk_wmesg = wmesg;
 615         lkp->lk_timo = timo;
 616         lkp->lk_lockholder = LK_NOTHREAD;
 617 }
 618
 619 /*
 620  * Reinitialize a lock that is being reused for a different purpose, but
 621  * which may have pending (blocked) threads sitting on it.  The caller
 622  * must already hold the interlock.
 623  */
 624 void
 625 lockreinit(struct lock *lkp, const char *wmesg, int timo, int flags)
 626 {
 627         spin_lock(&lkp->lk_spinlock);
 628         lkp->lk_flags = (lkp->lk_flags & ~LK_EXTFLG_MASK) |
 629                         (flags & LK_EXTFLG_MASK);
 630         lkp->lk_wmesg = wmesg;
 631         lkp->lk_timo = timo;
 632         spin_unlock(&lkp->lk_spinlock);
 633 }
 634
 635 /*
 636  * Requires that the caller is the exclusive owner of this lock.
 637  */
 638 void
 639 lockuninit(struct lock *l)
 640 {
 641         /*
 642          * At this point we should have removed all the references to this lock
 643          * so there can't be anyone waiting on it.
 644          */
 645         KKASSERT(l->lk_waitcount == 0);
 646
 647         spin_uninit(&l->lk_spinlock);
 648 }
 649
 650 /*
 651  * Determine the status of a lock.
 652  */
 653 int
 654 lockstatus(struct lock *lkp, struct thread *td)
 655 {
 656         int lock_type = 0;
 657
 658         spin_lock(&lkp->lk_spinlock);
 659         if (lkp->lk_exclusivecount != 0) {
 660                 if (td == NULL || lkp->lk_lockholder == td)
 661                         lock_type = LK_EXCLUSIVE;
 662                 else
 663                         lock_type = LK_EXCLOTHER;
 664         } else if (lkp->lk_sharecount != 0) {
 665                 lock_type = LK_SHARED;
 666         }
 667         spin_unlock(&lkp->lk_spinlock);
 668         return (lock_type);
 669 }
 670
 671 /*
 672  * Return non-zero if the caller owns the lock shared or exclusive.
 673  * We can only guess re: shared locks.
 674  */
 675 int
 676 lockowned(struct lock *lkp)
 677 {
 678         thread_t td = curthread;
 679
 680         if (lkp->lk_exclusivecount)
 681                 return(lkp->lk_lockholder == td);
 682         return(lkp->lk_sharecount != 0);
 683 }
 684
 685 /*
 686  * Determine the number of holders of a lock.
 687  *
 688  * The non-blocking version can usually be used for assertions.
 689  */
 690 int
 691 lockcount(struct lock *lkp)
 692 {
 693         int count;
 694
 695         spin_lock(&lkp->lk_spinlock);
 696         count = lkp->lk_exclusivecount + lkp->lk_sharecount;
 697         spin_unlock(&lkp->lk_spinlock);
 698         return (count);
 699 }
 700
 701 int
 702 lockcountnb(struct lock *lkp)
 703 {
 704         return (lkp->lk_exclusivecount + lkp->lk_sharecount);
 705 }
 706
 707 /*
 708  * Print out information about state of a lock. Used by VOP_PRINT
 709  * routines to display status about contained locks.
 710  */
 711 void
 712 lockmgr_printinfo(struct lock *lkp)
 713 {
 714         struct thread *td = lkp->lk_lockholder;
 715         struct proc *p;
 716
 717         if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
 718                 p = td->td_proc;
 719         else
 720                 p = NULL;
 721
 722         if (lkp->lk_sharecount)
 723                 kprintf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
 724                     lkp->lk_sharecount);
 725         else if (lkp->lk_flags & LK_HAVE_EXCL)
 726                 kprintf(" lock type %s: EXCL (count %d) by td %p pid %d",
 727                     lkp->lk_wmesg, lkp->lk_exclusivecount, td,
 728                     p ? p->p_pid : -99);
 729         if (lkp->lk_waitcount > 0)
 730                 kprintf(" with %d pending", lkp->lk_waitcount);
 731 }
 732
 733 void
 734 lock_sysinit(struct lock_args *arg)
 735 {
 736         lockinit(arg->la_lock, arg->la_desc, 0, arg->la_flags);
 737 }