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