kern_lock.c revision 161337
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 */ 42 43#include <sys/cdefs.h> 44__FBSDID("$FreeBSD: head/sys/kern/kern_lock.c 161337 2006-08-15 18:29:01Z jhb $"); 45 46#include "opt_ddb.h" 47 48#include <sys/param.h> 49#include <sys/kdb.h> 50#include <sys/kernel.h> 51#include <sys/ktr.h> 52#include <sys/lock.h> 53#include <sys/lockmgr.h> 54#include <sys/mutex.h> 55#include <sys/proc.h> 56#include <sys/systm.h> 57#ifdef DEBUG_LOCKS 58#include <sys/stack.h> 59#endif 60 61#ifdef DDB 62#include <ddb/ddb.h> 63#endif 64 65/* 66 * Locking primitives implementation. 67 * Locks provide shared/exclusive sychronization. 68 */ 69 70#define COUNT(td, x) if ((td)) (td)->td_locks += (x) 71#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 72 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 73 74static int acquire(struct lock **lkpp, int extflags, int wanted); 75static int acquiredrain(struct lock *lkp, int extflags) ; 76 77static __inline void 78sharelock(struct thread *td, struct lock *lkp, int incr) { 79 lkp->lk_flags |= LK_SHARE_NONZERO; 80 lkp->lk_sharecount += incr; 81 COUNT(td, incr); 82} 83 84static __inline void 85shareunlock(struct thread *td, struct lock *lkp, int decr) { 86 87 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 88 89 COUNT(td, -decr); 90 if (lkp->lk_sharecount == decr) { 91 lkp->lk_flags &= ~LK_SHARE_NONZERO; 92 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 93 wakeup(lkp); 94 } 95 lkp->lk_sharecount = 0; 96 } else { 97 lkp->lk_sharecount -= decr; 98 } 99} 100 101static int 102acquire(struct lock **lkpp, int extflags, int wanted) 103{ 104 struct lock *lkp = *lkpp; 105 int error; 106 CTR3(KTR_LOCK, 107 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", 108 lkp, extflags, wanted); 109 110 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) 111 return EBUSY; 112 error = 0; 113 while ((lkp->lk_flags & wanted) != 0) { 114 CTR2(KTR_LOCK, 115 "acquire(): lkp == %p, lk_flags == 0x%x sleeping", 116 lkp, lkp->lk_flags); 117 lkp->lk_flags |= LK_WAIT_NONZERO; 118 lkp->lk_waitcount++; 119 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio, 120 lkp->lk_wmesg, 121 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 122 lkp->lk_waitcount--; 123 if (lkp->lk_waitcount == 0) 124 lkp->lk_flags &= ~LK_WAIT_NONZERO; 125 if (error) 126 break; 127 if (extflags & LK_SLEEPFAIL) { 128 error = ENOLCK; 129 break; 130 } 131 if (lkp->lk_newlock != NULL) { 132 mtx_lock(lkp->lk_newlock->lk_interlock); 133 mtx_unlock(lkp->lk_interlock); 134 if (lkp->lk_waitcount == 0) 135 wakeup((void *)(&lkp->lk_newlock)); 136 *lkpp = lkp = lkp->lk_newlock; 137 } 138 } 139 mtx_assert(lkp->lk_interlock, MA_OWNED); 140 return (error); 141} 142 143/* 144 * Set, change, or release a lock. 145 * 146 * Shared requests increment the shared count. Exclusive requests set the 147 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 148 * accepted shared locks and shared-to-exclusive upgrades to go away. 149 */ 150int 151lockmgr(lkp, flags, interlkp, td) 152 struct lock *lkp; 153 u_int flags; 154 struct mtx *interlkp; 155 struct thread *td; 156{ 157 int error; 158 struct thread *thr; 159 int extflags, lockflags; 160 161 error = 0; 162 if (td == NULL) 163 thr = LK_KERNPROC; 164 else 165 thr = td; 166 167 if ((flags & LK_INTERNAL) == 0) 168 mtx_lock(lkp->lk_interlock); 169 CTR6(KTR_LOCK, 170 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, " 171 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder, 172 lkp->lk_exclusivecount, flags, td); 173#ifdef DEBUG_LOCKS 174 { 175 struct stack stack; /* XXX */ 176 stack_save(&stack); 177 CTRSTACK(KTR_LOCK, &stack, 0, 1); 178 } 179#endif 180 181 if (flags & LK_INTERLOCK) { 182 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED); 183 mtx_unlock(interlkp); 184 } 185 186 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0) 187 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, 188 &lkp->lk_interlock->mtx_object, 189 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg); 190 191 if (panicstr != NULL) { 192 mtx_unlock(lkp->lk_interlock); 193 return (0); 194 } 195 if ((lkp->lk_flags & LK_NOSHARE) && 196 (flags & LK_TYPE_MASK) == LK_SHARED) { 197 flags &= ~LK_TYPE_MASK; 198 flags |= LK_EXCLUSIVE; 199 } 200 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 201 202 switch (flags & LK_TYPE_MASK) { 203 204 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 TDP_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 != thr) { 215 lockflags = LK_HAVE_EXCL; 216 if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT)) 217 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; 218 error = acquire(&lkp, extflags, lockflags); 219 if (error) 220 break; 221 sharelock(td, lkp, 1); 222#if defined(DEBUG_LOCKS) 223 stack_save(&lkp->lk_stack); 224#endif 225 break; 226 } 227 /* 228 * We hold an exclusive lock, so downgrade it to shared. 229 * An alternative would be to fail with EDEADLK. 230 */ 231 sharelock(td, lkp, 1); 232 /* FALLTHROUGH downgrade */ 233 234 case LK_DOWNGRADE: 235 KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0, 236 ("lockmgr: not holding exclusive lock " 237 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0", 238 lkp->lk_lockholder, thr, lkp->lk_exclusivecount)); 239 sharelock(td, lkp, lkp->lk_exclusivecount); 240 COUNT(td, -lkp->lk_exclusivecount); 241 lkp->lk_exclusivecount = 0; 242 lkp->lk_flags &= ~LK_HAVE_EXCL; 243 lkp->lk_lockholder = LK_NOPROC; 244 if (lkp->lk_waitcount) 245 wakeup((void *)lkp); 246 break; 247 248 case LK_EXCLUPGRADE: 249 /* 250 * If another process is ahead of us to get an upgrade, 251 * then we want to fail rather than have an intervening 252 * exclusive access. 253 */ 254 if (lkp->lk_flags & LK_WANT_UPGRADE) { 255 shareunlock(td, lkp, 1); 256 error = EBUSY; 257 break; 258 } 259 /* FALLTHROUGH normal upgrade */ 260 261 case LK_UPGRADE: 262 /* 263 * Upgrade a shared lock to an exclusive one. If another 264 * shared lock has already requested an upgrade to an 265 * exclusive lock, our shared lock is released and an 266 * exclusive lock is requested (which will be granted 267 * after the upgrade). If we return an error, the file 268 * will always be unlocked. 269 */ 270 if (lkp->lk_lockholder == thr) 271 panic("lockmgr: upgrade exclusive lock"); 272 if (lkp->lk_sharecount <= 0) 273 panic("lockmgr: upgrade without shared"); 274 shareunlock(td, lkp, 1); 275 /* 276 * If we are just polling, check to see if we will block. 277 */ 278 if ((extflags & LK_NOWAIT) && 279 ((lkp->lk_flags & LK_WANT_UPGRADE) || 280 lkp->lk_sharecount > 1)) { 281 error = EBUSY; 282 break; 283 } 284 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) { 285 /* 286 * We are first shared lock to request an upgrade, so 287 * request upgrade and wait for the shared count to 288 * drop to zero, then take exclusive lock. 289 */ 290 lkp->lk_flags |= LK_WANT_UPGRADE; 291 error = acquire(&lkp, extflags, LK_SHARE_NONZERO); 292 lkp->lk_flags &= ~LK_WANT_UPGRADE; 293 294 if (error) { 295 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO)) 296 wakeup((void *)lkp); 297 break; 298 } 299 if (lkp->lk_exclusivecount != 0) 300 panic("lockmgr: non-zero exclusive count"); 301 lkp->lk_flags |= LK_HAVE_EXCL; 302 lkp->lk_lockholder = thr; 303 lkp->lk_exclusivecount = 1; 304 COUNT(td, 1); 305#if defined(DEBUG_LOCKS) 306 stack_save(&lkp->lk_stack); 307#endif 308 break; 309 } 310 /* 311 * Someone else has requested upgrade. Release our shared 312 * lock, awaken upgrade requestor if we are the last shared 313 * lock, then request an exclusive lock. 314 */ 315 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 316 LK_WAIT_NONZERO) 317 wakeup((void *)lkp); 318 /* FALLTHROUGH exclusive request */ 319 320 case LK_EXCLUSIVE: 321 if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) { 322 /* 323 * Recursive lock. 324 */ 325 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 326 panic("lockmgr: locking against myself"); 327 if ((extflags & LK_CANRECURSE) != 0) { 328 lkp->lk_exclusivecount++; 329 COUNT(td, 1); 330 break; 331 } 332 } 333 /* 334 * If we are just polling, check to see if we will sleep. 335 */ 336 if ((extflags & LK_NOWAIT) && 337 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) { 338 error = EBUSY; 339 break; 340 } 341 /* 342 * Try to acquire the want_exclusive flag. 343 */ 344 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL)); 345 if (error) 346 break; 347 lkp->lk_flags |= LK_WANT_EXCL; 348 /* 349 * Wait for shared locks and upgrades to finish. 350 */ 351 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO); 352 lkp->lk_flags &= ~LK_WANT_EXCL; 353 if (error) { 354 if (lkp->lk_flags & LK_WAIT_NONZERO) 355 wakeup((void *)lkp); 356 break; 357 } 358 lkp->lk_flags |= LK_HAVE_EXCL; 359 lkp->lk_lockholder = thr; 360 if (lkp->lk_exclusivecount != 0) 361 panic("lockmgr: non-zero exclusive count"); 362 lkp->lk_exclusivecount = 1; 363 COUNT(td, 1); 364#if defined(DEBUG_LOCKS) 365 stack_save(&lkp->lk_stack); 366#endif 367 break; 368 369 case LK_RELEASE: 370 if (lkp->lk_exclusivecount != 0) { 371 if (lkp->lk_lockholder != thr && 372 lkp->lk_lockholder != LK_KERNPROC) { 373 panic("lockmgr: thread %p, not %s %p unlocking", 374 thr, "exclusive lock holder", 375 lkp->lk_lockholder); 376 } 377 if (lkp->lk_lockholder != LK_KERNPROC) 378 COUNT(td, -1); 379 if (lkp->lk_exclusivecount == 1) { 380 lkp->lk_flags &= ~LK_HAVE_EXCL; 381 lkp->lk_lockholder = LK_NOPROC; 382 lkp->lk_exclusivecount = 0; 383 } else { 384 lkp->lk_exclusivecount--; 385 } 386 } else if (lkp->lk_flags & LK_SHARE_NONZERO) 387 shareunlock(td, lkp, 1); 388 else { 389 printf("lockmgr: thread %p unlocking unheld lock\n", 390 thr); 391 kdb_backtrace(); 392 } 393 394 if (lkp->lk_flags & LK_WAIT_NONZERO) 395 wakeup((void *)lkp); 396 break; 397 398 case LK_DRAIN: 399 /* 400 * Check that we do not already hold the lock, as it can 401 * never drain if we do. Unfortunately, we have no way to 402 * check for holding a shared lock, but at least we can 403 * check for an exclusive one. 404 */ 405 if (lkp->lk_lockholder == thr) 406 panic("lockmgr: draining against myself"); 407 408 error = acquiredrain(lkp, extflags); 409 if (error) 410 break; 411 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 412 lkp->lk_lockholder = thr; 413 lkp->lk_exclusivecount = 1; 414 COUNT(td, 1); 415#if defined(DEBUG_LOCKS) 416 stack_save(&lkp->lk_stack); 417#endif 418 break; 419 420 default: 421 mtx_unlock(lkp->lk_interlock); 422 panic("lockmgr: unknown locktype request %d", 423 flags & LK_TYPE_MASK); 424 /* NOTREACHED */ 425 } 426 if ((lkp->lk_flags & LK_WAITDRAIN) && 427 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 428 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 429 lkp->lk_flags &= ~LK_WAITDRAIN; 430 wakeup((void *)&lkp->lk_flags); 431 } 432 mtx_unlock(lkp->lk_interlock); 433 return (error); 434} 435 436static int 437acquiredrain(struct lock *lkp, int extflags) { 438 int error; 439 440 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 441 return EBUSY; 442 } 443 while (lkp->lk_flags & LK_ALL) { 444 lkp->lk_flags |= LK_WAITDRAIN; 445 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio, 446 lkp->lk_wmesg, 447 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 448 if (error) 449 return error; 450 if (extflags & LK_SLEEPFAIL) { 451 return ENOLCK; 452 } 453 } 454 return 0; 455} 456 457/* 458 * Transfer any waiting processes from one lock to another. 459 */ 460void 461transferlockers(from, to) 462 struct lock *from; 463 struct lock *to; 464{ 465 466 KASSERT(from != to, ("lock transfer to self")); 467 KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock")); 468 469 mtx_lock(from->lk_interlock); 470 if (from->lk_waitcount == 0) { 471 mtx_unlock(from->lk_interlock); 472 return; 473 } 474 from->lk_newlock = to; 475 wakeup((void *)from); 476 msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio, 477 "lkxfer", 0); 478 from->lk_newlock = NULL; 479 from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE); 480 KASSERT(from->lk_waitcount == 0, ("active lock")); 481 mtx_unlock(from->lk_interlock); 482} 483 484 485/* 486 * Initialize a lock; required before use. 487 */ 488void 489lockinit(lkp, prio, wmesg, timo, flags) 490 struct lock *lkp; 491 int prio; 492 const char *wmesg; 493 int timo; 494 int flags; 495{ 496 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", " 497 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags); 498 499 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder); 500 lkp->lk_flags = (flags & LK_EXTFLG_MASK); 501 lkp->lk_sharecount = 0; 502 lkp->lk_waitcount = 0; 503 lkp->lk_exclusivecount = 0; 504 lkp->lk_prio = prio; 505 lkp->lk_wmesg = wmesg; 506 lkp->lk_timo = timo; 507 lkp->lk_lockholder = LK_NOPROC; 508 lkp->lk_newlock = NULL; 509#ifdef DEBUG_LOCKS 510 stack_zero(&lkp->lk_stack); 511#endif 512} 513 514/* 515 * Destroy a lock. 516 */ 517void 518lockdestroy(lkp) 519 struct lock *lkp; 520{ 521 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", 522 lkp, lkp->lk_wmesg); 523} 524 525/* 526 * Determine the status of a lock. 527 */ 528int 529lockstatus(lkp, td) 530 struct lock *lkp; 531 struct thread *td; 532{ 533 int lock_type = 0; 534 int interlocked; 535 536 if (!kdb_active) { 537 interlocked = 1; 538 mtx_lock(lkp->lk_interlock); 539 } else 540 interlocked = 0; 541 if (lkp->lk_exclusivecount != 0) { 542 if (td == NULL || lkp->lk_lockholder == td) 543 lock_type = LK_EXCLUSIVE; 544 else 545 lock_type = LK_EXCLOTHER; 546 } else if (lkp->lk_sharecount != 0) 547 lock_type = LK_SHARED; 548 if (interlocked) 549 mtx_unlock(lkp->lk_interlock); 550 return (lock_type); 551} 552 553/* 554 * Determine the number of holders of a lock. 555 */ 556int 557lockcount(lkp) 558 struct lock *lkp; 559{ 560 int count; 561 562 mtx_lock(lkp->lk_interlock); 563 count = lkp->lk_exclusivecount + lkp->lk_sharecount; 564 mtx_unlock(lkp->lk_interlock); 565 return (count); 566} 567 568/* 569 * Print out information about state of a lock. Used by VOP_PRINT 570 * routines to display status about contained locks. 571 */ 572void 573lockmgr_printinfo(lkp) 574 struct lock *lkp; 575{ 576 577 if (lkp->lk_sharecount) 578 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 579 lkp->lk_sharecount); 580 else if (lkp->lk_flags & LK_HAVE_EXCL) 581 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)", 582 lkp->lk_wmesg, lkp->lk_exclusivecount, 583 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); 584 if (lkp->lk_waitcount > 0) 585 printf(" with %d pending", lkp->lk_waitcount); 586#ifdef DEBUG_LOCKS 587 stack_print(&lkp->lk_stack); 588#endif 589} 590 591#ifdef DDB 592/* 593 * Check to see if a thread that is blocked on a sleep queue is actually 594 * blocked on a 'struct lock'. If so, output some details and return true. 595 * If the lock has an exclusive owner, return that in *ownerp. 596 */ 597int 598lockmgr_chain(struct thread *td, struct thread **ownerp) 599{ 600 struct lock *lkp; 601 602 lkp = td->td_wchan; 603 604 /* Simple test to see if wchan points to a lockmgr lock. */ 605 if (lkp->lk_wmesg != td->td_wmesg) 606 return (0); 607 608 /* Ok, we think we have a lockmgr lock, so output some details. */ 609 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); 610 if (lkp->lk_sharecount) { 611 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 612 *ownerp = NULL; 613 } else { 614 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); 615 *ownerp = lkp->lk_lockholder; 616 } 617 return (1); 618} 619 620DB_SHOW_COMMAND(lockmgr, db_show_lockmgr) 621{ 622 struct thread *td; 623 struct lock *lkp; 624 625 if (!have_addr) 626 return; 627 lkp = (struct lock *)addr; 628 629 db_printf("lock type: %s\n", lkp->lk_wmesg); 630 db_printf("state: "); 631 if (lkp->lk_sharecount) 632 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 633 else if (lkp->lk_flags & LK_HAVE_EXCL) { 634 td = lkp->lk_lockholder; 635 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); 636 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, 637 td->td_proc->p_pid, td->td_proc->p_comm); 638 } else 639 db_printf("UNLOCKED\n"); 640 if (lkp->lk_waitcount > 0) 641 db_printf("waiters: %d\n", lkp->lk_waitcount); 642} 643#endif 644