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         lkp->lk_flags |= LK_SHARE_NONZERO;
  85         lkp->lk_sharecount += incr;
  86 }
  87
  88 static LOCK_INLINE int
  89 shareunlock(struct lock *lkp, int decr)
  90 {
  91         int dowakeup = 0;
  92
  93         KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
  94
  95         if (lkp->lk_sharecount == decr) {
  96                 lkp->lk_flags &= ~LK_SHARE_NONZERO;
  97                 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
  98                         dowakeup = 1;
  99                 }
 100                 lkp->lk_sharecount = 0;
 101         } else {
 102                 lkp->lk_sharecount -= decr;
 103         }
 104         return(dowakeup);
 105 }
 106
 107 /*
 108  * lock acquisition helper routine.  Called with the lock's spinlock held.
 109  */
 110 static int
 111 acquire(struct lock *lkp, int extflags, int wanted)
 112 {
 113         int error;
 114
 115         if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
 116                 return EBUSY;
 117         }
 118
 119         while ((lkp->lk_flags & wanted) != 0) {
 120                 lkp->lk_flags |= LK_WAIT_NONZERO;
 121                 lkp->lk_waitcount++;
 122
 123                 /*
 124                  * Atomic spinlock release/sleep/reacquire.
 125                  */
 126                 error = ssleep(lkp, &lkp->lk_spinlock,
 127                                ((extflags & LK_PCATCH) ? PCATCH : 0),
 128                                lkp->lk_wmesg,
 129                                ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
 130                 if (lkp->lk_waitcount == 1) {
 131                         lkp->lk_flags &= ~LK_WAIT_NONZERO;
 132                         lkp->lk_waitcount = 0;
 133                 } else {
 134                         lkp->lk_waitcount--;
 135                 }
 136                 if (error)
 137                         return error;
 138                 if (extflags & LK_SLEEPFAIL)
 139                         return ENOLCK;
 140         }
 141         return 0;
 142 }
 143
 144 /*
 145  * Set, change, or release a lock.
 146  *
 147  * Shared requests increment the shared count. Exclusive requests set the
 148  * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
 149  * accepted shared locks and shared-to-exclusive upgrades to go away.
 150  *
 151  * A spinlock is held for most of the procedure.  We must not do anything
 152  * fancy while holding the spinlock.
 153  */
 154 int
 155 #ifndef DEBUG_LOCKS
 156 lockmgr(struct lock *lkp, u_int flags)
 157 #else
 158 debuglockmgr(struct lock *lkp, u_int flags,
 159              const char *name, const char *file, int line)
 160 #endif
 161 {
 162         thread_t td;
 163         int error;
 164         int extflags;
 165         int dowakeup;
 166 #ifdef DEBUG_LOCKS
 167         int i;
 168 #endif
 169
 170         error = 0;
 171         dowakeup = 0;
 172
 173         if (mycpu->gd_intr_nesting_level &&
 174             (flags & LK_NOWAIT) == 0 &&
 175             (flags & LK_TYPE_MASK) != LK_RELEASE &&
 176             panic_cpu_gd != mycpu
 177         ) {
 178
 179 #ifndef DEBUG_LOCKS
 180                 panic("lockmgr %s from %p: called from interrupt, ipi, "
 181                       "or hard code section",
 182                       lkp->lk_wmesg, ((int **)&lkp)[-1]);
 183 #else
 184                 panic("lockmgr %s from %s:%d: called from interrupt, ipi, "
 185                       "or hard code section",
 186                       lkp->lk_wmesg, file, line);
 187 #endif
 188         }
 189
 190 #ifdef DEBUG_LOCKS
 191         if (mycpu->gd_spinlocks_wr &&
 192             ((flags & LK_NOWAIT) == 0)
 193         ) {
 194                 panic("lockmgr %s from %s:%d: called with %d spinlocks held",
 195                       lkp->lk_wmesg, file, line, mycpu->gd_spinlocks_wr);
 196         }
 197 #endif
 198
 199         spin_lock(&lkp->lk_spinlock);
 200
 201         extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
 202         td = curthread;
 203
 204         switch (flags & LK_TYPE_MASK) {
 205         case LK_SHARED:
 206                 /*
 207                  * If we are not the exclusive lock holder, we have to block
 208                  * while there is an exclusive lock holder or while an
 209                  * exclusive lock request or upgrade request is in progress.
 210                  *
 211                  * However, if TDF_DEADLKTREAT is set, we override exclusive
 212                  * lock requests or upgrade requests ( but not the exclusive
 213                  * lock itself ).
 214                  */
 215                 if (lkp->lk_lockholder != td) {
 216                         if (td->td_flags & TDF_DEADLKTREAT) {
 217                                 error = acquire(
 218                                             lkp,
 219                                             extflags,
 220                                             LK_HAVE_EXCL
 221                                         );
 222                         } else {
 223                                 error = acquire(
 224                                             lkp,
 225                                             extflags,
 226                                             LK_HAVE_EXCL | LK_WANT_EXCL |
 227                                              LK_WANT_UPGRADE
 228                                         );
 229                         }
 230                         if (error)
 231                                 break;
 232                         sharelock(lkp, 1);
 233                         COUNT(td, 1);
 234                         break;
 235                 }
 236                 /*
 237                  * We hold an exclusive lock, so downgrade it to shared.
 238                  * An alternative would be to fail with EDEADLK.
 239                  */
 240                 sharelock(lkp, 1);
 241                 COUNT(td, 1);
 242                 /* fall into downgrade */
 243
 244         case LK_DOWNGRADE:
 245                 if (lkp->lk_lockholder != td || lkp->lk_exclusivecount == 0) {
 246                         spin_unlock(&lkp->lk_spinlock);
 247                         panic("lockmgr: not holding exclusive lock");
 248                 }
 249
 250 #ifdef DEBUG_LOCKS
 251                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 252                         if (td->td_lockmgr_stack[i] == lkp &&
 253                             td->td_lockmgr_stack_id[i] > 0
 254                         ) {
 255                                 td->td_lockmgr_stack_id[i]--;
 256                                 break;
 257                         }
 258                 }
 259 #endif
 260
 261                 sharelock(lkp, lkp->lk_exclusivecount);
 262                 lkp->lk_exclusivecount = 0;
 263                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 264                 lkp->lk_lockholder = LK_NOTHREAD;
 265                 if (lkp->lk_waitcount)
 266                         dowakeup = 1;
 267                 break;
 268
 269         case LK_EXCLUPGRADE:
 270                 /*
 271                  * If another process is ahead of us to get an upgrade,
 272                  * then we want to fail rather than have an intervening
 273                  * exclusive access.
 274                  */
 275                 if (lkp->lk_flags & LK_WANT_UPGRADE) {
 276                         dowakeup = shareunlock(lkp, 1);
 277                         COUNT(td, -1);
 278                         error = EBUSY;
 279                         break;
 280                 }
 281                 /* fall into normal upgrade */
 282
 283         case LK_UPGRADE:
 284                 /*
 285                  * Upgrade a shared lock to an exclusive one. If another
 286                  * shared lock has already requested an upgrade to an
 287                  * exclusive lock, our shared lock is released and an
 288                  * exclusive lock is requested (which will be granted
 289                  * after the upgrade). If we return an error, the file
 290                  * will always be unlocked.
 291                  */
 292                 if ((lkp->lk_lockholder == td) || (lkp->lk_sharecount <= 0)) {
 293                         spin_unlock(&lkp->lk_spinlock);
 294                         panic("lockmgr: upgrade exclusive lock");
 295                 }
 296                 dowakeup += shareunlock(lkp, 1);
 297                 COUNT(td, -1);
 298                 /*
 299                  * If we are just polling, check to see if we will block.
 300                  */
 301                 if ((extflags & LK_NOWAIT) &&
 302                     ((lkp->lk_flags & LK_WANT_UPGRADE) ||
 303                      lkp->lk_sharecount > 1)) {
 304                         error = EBUSY;
 305                         break;
 306                 }
 307                 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
 308                         /*
 309                          * We are first shared lock to request an upgrade, so
 310                          * request upgrade and wait for the shared count to
 311                          * drop to zero, then take exclusive lock.
 312                          *
 313                          * Although I don't think this can occur for
 314                          * robustness we also wait for any exclusive locks
 315                          * to be released.  LK_WANT_UPGRADE is supposed to
 316                          * prevent new exclusive locks but might not in the
 317                          * future.
 318                          */
 319                         lkp->lk_flags |= LK_WANT_UPGRADE;
 320                         error = acquire(lkp, extflags,
 321                                         LK_HAVE_EXCL | LK_SHARE_NONZERO);
 322                         lkp->lk_flags &= ~LK_WANT_UPGRADE;
 323
 324                         if (error)
 325                                 break;
 326                         lkp->lk_flags |= LK_HAVE_EXCL;
 327                         lkp->lk_lockholder = td;
 328                         if (lkp->lk_exclusivecount != 0) {
 329                                 spin_unlock(&lkp->lk_spinlock);
 330                                 panic("lockmgr(1): non-zero exclusive count");
 331                         }
 332                         lkp->lk_exclusivecount = 1;
 333 #if defined(DEBUG_LOCKS)
 334                         lkp->lk_filename = file;
 335                         lkp->lk_lineno = line;
 336                         lkp->lk_lockername = name;
 337
 338                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 339                                 /*
 340                                  * Recursive lockmgr path
 341                                  */
 342                                 if (td->td_lockmgr_stack[i] == lkp &&
 343                                     td->td_lockmgr_stack_id[i] != 0
 344                                 ) {
 345                                         td->td_lockmgr_stack_id[i]++;
 346                                         goto lkmatch2;
 347                                 }
 348                        }
 349
 350                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 351                                 /*
 352                                  * Use new lockmgr tracking slot
 353                                  */
 354                                 if (td->td_lockmgr_stack_id[i] == 0) {
 355                                         td->td_lockmgr_stack_id[i]++;
 356                                         td->td_lockmgr_stack[i] = lkp;
 357                                         break;
 358                                 }
 359                         }
 360 lkmatch2:
 361                         ;
 362 #endif
 363                         COUNT(td, 1);
 364                         break;
 365                 }
 366                 /*
 367                  * Someone else has requested upgrade. Release our shared
 368                  * lock, awaken upgrade requestor if we are the last shared
 369                  * lock, then request an exclusive lock.
 370                  */
 371                 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
 372                         LK_WAIT_NONZERO) {
 373                         ++dowakeup;
 374                 }
 375                 /* fall into exclusive request */
 376
 377         case LK_EXCLUSIVE:
 378                 if (lkp->lk_lockholder == td && td != LK_KERNTHREAD) {
 379                         /*
 380                          *      Recursive lock.
 381                          */
 382                         if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) {
 383                                 spin_unlock(&lkp->lk_spinlock);
 384                                 panic("lockmgr: locking against myself");
 385                         }
 386                         if ((extflags & LK_CANRECURSE) != 0) {
 387                                 lkp->lk_exclusivecount++;
 388                                 COUNT(td, 1);
 389                                 break;
 390                         }
 391                 }
 392                 /*
 393                  * If we are just polling, check to see if we will sleep.
 394                  */
 395                 if ((extflags & LK_NOWAIT) &&
 396                     (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL |
 397                                       LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
 398                         error = EBUSY;
 399                         break;
 400                 }
 401                 /*
 402                  * Wait for exclusive lock holders to release and try to
 403                  * acquire the want_exclusive flag.
 404                  */
 405                 error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
 406                 if (error)
 407                         break;
 408                 lkp->lk_flags |= LK_WANT_EXCL;
 409
 410                 /*
 411                  * Wait for shared locks and upgrades to finish.  We can lose
 412                  * the race against a successful shared lock upgrade in which
 413                  * case LK_HAVE_EXCL will get set regardless of our
 414                  * acquisition of LK_WANT_EXCL, so we have to acquire
 415                  * LK_HAVE_EXCL here as well.
 416                  */
 417                 error = acquire(lkp, extflags, LK_HAVE_EXCL |
 418                                                LK_WANT_UPGRADE |
 419                                                LK_SHARE_NONZERO);
 420                 lkp->lk_flags &= ~LK_WANT_EXCL;
 421                 if (error)
 422                         break;
 423                 lkp->lk_flags |= LK_HAVE_EXCL;
 424                 lkp->lk_lockholder = td;
 425                 if (lkp->lk_exclusivecount != 0) {
 426                         spin_unlock(&lkp->lk_spinlock);
 427                         panic("lockmgr(2): non-zero exclusive count");
 428                 }
 429                 lkp->lk_exclusivecount = 1;
 430 #if defined(DEBUG_LOCKS)
 431                 lkp->lk_filename = file;
 432                 lkp->lk_lineno = line;
 433                 lkp->lk_lockername = name;
 434
 435                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 436                         /*
 437                          * Recursive lockmgr path
 438                          */
 439                         if (td->td_lockmgr_stack[i] == lkp &&
 440                             td->td_lockmgr_stack_id[i] != 0
 441                         ) {
 442                                 td->td_lockmgr_stack_id[i]++;
 443                                 goto lkmatch1;
 444                         }
 445                 }
 446
 447                 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 448                         /*
 449                          * Use new lockmgr tracking slot
 450                          */
 451                         if (td->td_lockmgr_stack_id[i] == 0) {
 452                                 td->td_lockmgr_stack_id[i]++;
 453                                 td->td_lockmgr_stack[i] = lkp;
 454                                 break;
 455                         }
 456                 }
 457 lkmatch1:
 458                 ;
 459 #endif
 460                 COUNT(td, 1);
 461                 break;
 462
 463         case LK_RELEASE:
 464                 if (lkp->lk_exclusivecount != 0) {
 465                         if (lkp->lk_lockholder != td &&
 466                             lkp->lk_lockholder != LK_KERNTHREAD) {
 467                                 spin_unlock(&lkp->lk_spinlock);
 468                                 panic("lockmgr: pid %d, not %s thr %p/%p unlocking",
 469                                     (td->td_proc ? td->td_proc->p_pid : -1),
 470                                     "exclusive lock holder",
 471                                     td, lkp->lk_lockholder);
 472                         }
 473                         if (lkp->lk_lockholder != LK_KERNTHREAD) {
 474                                 COUNT(td, -1);
 475                         }
 476                         if (lkp->lk_exclusivecount == 1) {
 477                                 lkp->lk_flags &= ~LK_HAVE_EXCL;
 478                                 lkp->lk_lockholder = LK_NOTHREAD;
 479                                 lkp->lk_exclusivecount = 0;
 480                         } else {
 481                                 lkp->lk_exclusivecount--;
 482                         }
 483 #ifdef DEBUG_LOCKS
 484                         for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) {
 485                                 if (td->td_lockmgr_stack[i] == lkp &&
 486                                     td->td_lockmgr_stack_id[i] > 0
 487                                 ) {
 488                                         td->td_lockmgr_stack_id[i]--;
 489                                         break;
 490                                 }
 491                         }
 492 #endif
 493                 } else if (lkp->lk_flags & LK_SHARE_NONZERO) {
 494                         dowakeup += shareunlock(lkp, 1);
 495                         COUNT(td, -1);
 496                 }
 497                 if (lkp->lk_flags & LK_WAIT_NONZERO)
 498                         ++dowakeup;
 499                 break;
 500
 501         default:
 502                 spin_unlock(&lkp->lk_spinlock);
 503                 panic("lockmgr: unknown locktype request %d",
 504                     flags & LK_TYPE_MASK);
 505                 /* NOTREACHED */
 506         }
 507         spin_unlock(&lkp->lk_spinlock);
 508         if (dowakeup)
 509                 wakeup(lkp);
 510         return (error);
 511 }
 512
 513 void
 514 lockmgr_kernproc(struct lock *lp)
 515 {
 516         struct thread *td __debugvar = curthread;
 517
 518         if (lp->lk_lockholder != LK_KERNTHREAD) {
 519                 KASSERT(lp->lk_lockholder == td,
 520                     ("lockmgr_kernproc: lock not owned by curthread %p", td));
 521                 COUNT(td, -1);
 522                 lp->lk_lockholder = LK_KERNTHREAD;
 523         }
 524 }
 525
 526 #if 0
 527 /*
 528  * Set the lock to be exclusively held.  The caller is holding the lock's
 529  * spinlock and the spinlock remains held on return.  A panic will occur
 530  * if the lock cannot be set to exclusive.
 531  */
 532 void
 533 lockmgr_setexclusive_interlocked(struct lock *lkp)
 534 {
 535         thread_t td = curthread;
 536
 537         KKASSERT((lkp->lk_flags & (LK_HAVE_EXCL|LK_SHARE_NONZERO)) == 0);
 538         KKASSERT(lkp->lk_exclusivecount == 0);
 539         lkp->lk_flags |= LK_HAVE_EXCL;
 540         lkp->lk_lockholder = td;
 541         lkp->lk_exclusivecount = 1;
 542         COUNT(td, 1);
 543 }
 544
 545 /*
 546  * Clear the caller's exclusive lock.  The caller is holding the lock's
 547  * spinlock.  THIS FUNCTION WILL UNLOCK THE SPINLOCK.
 548  *
 549  * A panic will occur if the caller does not hold the lock.
 550  */
 551 void
 552 lockmgr_clrexclusive_interlocked(struct lock *lkp)
 553 {
 554         thread_t td __debugvar = curthread;
 555         int dowakeup = 0;
 556
 557         KKASSERT((lkp->lk_flags & LK_HAVE_EXCL) && lkp->lk_exclusivecount == 1
 558                  && lkp->lk_lockholder == td);
 559         lkp->lk_lockholder = LK_NOTHREAD;
 560         lkp->lk_flags &= ~LK_HAVE_EXCL;
 561         lkp->lk_exclusivecount = 0;
 562         if (lkp->lk_flags & LK_WAIT_NONZERO)
 563                 dowakeup = 1;
 564         COUNT(td, -1);
 565         spin_unlock(&lkp->lk_spinlock);
 566         if (dowakeup)
 567                 wakeup((void *)lkp);
 568 }
 569
 570 #endif
 571
 572 /*
 573  * Initialize a lock; required before use.
 574  */
 575 void
 576 lockinit(struct lock *lkp, char *wmesg, int timo, int flags)
 577 {
 578         spin_init(&lkp->lk_spinlock);
 579         lkp->lk_flags = (flags & LK_EXTFLG_MASK);
 580         lkp->lk_sharecount = 0;
 581         lkp->lk_waitcount = 0;
 582         lkp->lk_exclusivecount = 0;
 583         lkp->lk_wmesg = wmesg;
 584         lkp->lk_timo = timo;
 585         lkp->lk_lockholder = LK_NOTHREAD;
 586 }
 587
 588 /*
 589  * Reinitialize a lock that is being reused for a different purpose, but
 590  * which may have pending (blocked) threads sitting on it.  The caller
 591  * must already hold the interlock.
 592  */
 593 void
 594 lockreinit(struct lock *lkp, char *wmesg, int timo, int flags)
 595 {
 596         spin_lock(&lkp->lk_spinlock);
 597         lkp->lk_flags = (lkp->lk_flags & ~LK_EXTFLG_MASK) |
 598                         (flags & LK_EXTFLG_MASK);
 599         lkp->lk_wmesg = wmesg;
 600         lkp->lk_timo = timo;
 601         spin_unlock(&lkp->lk_spinlock);
 602 }
 603
 604 /*
 605  * Requires that the caller is the exclusive owner of this lock.
 606  */
 607 void
 608 lockuninit(struct lock *l)
 609 {
 610         /*
 611          * At this point we should have removed all the references to this lock
 612          * so there can't be anyone waiting on it.
 613          */
 614         KKASSERT(l->lk_waitcount == 0);
 615
 616         spin_uninit(&l->lk_spinlock);
 617 }
 618
 619 /*
 620  * Determine the status of a lock.
 621  */
 622 int
 623 lockstatus(struct lock *lkp, struct thread *td)
 624 {
 625         int lock_type = 0;
 626
 627         spin_lock(&lkp->lk_spinlock);
 628         if (lkp->lk_exclusivecount != 0) {
 629                 if (td == NULL || lkp->lk_lockholder == td)
 630                         lock_type = LK_EXCLUSIVE;
 631                 else
 632                         lock_type = LK_EXCLOTHER;
 633         } else if (lkp->lk_sharecount != 0) {
 634                 lock_type = LK_SHARED;
 635         }
 636         spin_unlock(&lkp->lk_spinlock);
 637         return (lock_type);
 638 }
 639
 640 /*
 641  * Return non-zero if the caller owns the lock shared or exclusive.
 642  * We can only guess re: shared locks.
 643  */
 644 int
 645 lockowned(struct lock *lkp)
 646 {
 647         thread_t td = curthread;
 648
 649         if (lkp->lk_exclusivecount)
 650                 return(lkp->lk_lockholder == td);
 651         return(lkp->lk_sharecount != 0);
 652 }
 653
 654 /*
 655  * Determine the number of holders of a lock.
 656  *
 657  * The non-blocking version can usually be used for assertions.
 658  */
 659 int
 660 lockcount(struct lock *lkp)
 661 {
 662         int count;
 663
 664         spin_lock(&lkp->lk_spinlock);
 665         count = lkp->lk_exclusivecount + lkp->lk_sharecount;
 666         spin_unlock(&lkp->lk_spinlock);
 667         return (count);
 668 }
 669
 670 int
 671 lockcountnb(struct lock *lkp)
 672 {
 673         return (lkp->lk_exclusivecount + lkp->lk_sharecount);
 674 }
 675
 676 /*
 677  * Print out information about state of a lock. Used by VOP_PRINT
 678  * routines to display status about contained locks.
 679  */
 680 void
 681 lockmgr_printinfo(struct lock *lkp)
 682 {
 683         struct thread *td = lkp->lk_lockholder;
 684         struct proc *p;
 685
 686         if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
 687                 p = td->td_proc;
 688         else
 689                 p = NULL;
 690
 691         if (lkp->lk_sharecount)
 692                 kprintf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
 693                     lkp->lk_sharecount);
 694         else if (lkp->lk_flags & LK_HAVE_EXCL)
 695                 kprintf(" lock type %s: EXCL (count %d) by td %p pid %d",
 696                     lkp->lk_wmesg, lkp->lk_exclusivecount, td,
 697                     p ? p->p_pid : -99);
 698         if (lkp->lk_waitcount > 0)
 699                 kprintf(" with %d pending", lkp->lk_waitcount);
 700 }
 701