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