kern_lock.c revision 176039
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 176039 2008-02-06 13:26:01Z attilio $"); 45 46#include "opt_ddb.h" 47#include "opt_global.h" 48 49#include <sys/param.h> 50#include <sys/kdb.h> 51#include <sys/kernel.h> 52#include <sys/ktr.h> 53#include <sys/lock.h> 54#include <sys/lockmgr.h> 55#include <sys/mutex.h> 56#include <sys/proc.h> 57#include <sys/systm.h> 58#include <sys/lock_profile.h> 59#ifdef DEBUG_LOCKS 60#include <sys/stack.h> 61#endif 62 63#define LOCKMGR_TRYOP(x) ((x) & LK_NOWAIT) 64#define LOCKMGR_TRYW(x) (LOCKMGR_TRYOP((x)) ? LOP_TRYLOCK : 0) 65 66static void assert_lockmgr(struct lock_object *lock, int what); 67#ifdef DDB 68#include <ddb/ddb.h> 69static void db_show_lockmgr(struct lock_object *lock); 70#endif 71static void lock_lockmgr(struct lock_object *lock, int how); 72static int unlock_lockmgr(struct lock_object *lock); 73 74struct lock_class lock_class_lockmgr = { 75 .lc_name = "lockmgr", 76 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 77 .lc_assert = assert_lockmgr, 78#ifdef DDB 79 .lc_ddb_show = db_show_lockmgr, 80#endif 81 .lc_lock = lock_lockmgr, 82 .lc_unlock = unlock_lockmgr, 83}; 84 85/* 86 * Locking primitives implementation. 87 * Locks provide shared/exclusive sychronization. 88 */ 89 90void 91assert_lockmgr(struct lock_object *lock, int what) 92{ 93 94 panic("lockmgr locks do not support assertions"); 95} 96 97void 98lock_lockmgr(struct lock_object *lock, int how) 99{ 100 101 panic("lockmgr locks do not support sleep interlocking"); 102} 103 104int 105unlock_lockmgr(struct lock_object *lock) 106{ 107 108 panic("lockmgr locks do not support sleep interlocking"); 109} 110 111#define COUNT(td, x) ((td)->td_locks += (x)) 112#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 113 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 114 115static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime); 116static int acquiredrain(struct lock *lkp, int extflags) ; 117 118static __inline void 119sharelock(struct thread *td, struct lock *lkp, int incr) { 120 lkp->lk_flags |= LK_SHARE_NONZERO; 121 lkp->lk_sharecount += incr; 122 COUNT(td, incr); 123} 124 125static __inline void 126shareunlock(struct thread *td, struct lock *lkp, int decr) { 127 128 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 129 130 COUNT(td, -decr); 131 if (lkp->lk_sharecount == decr) { 132 lkp->lk_flags &= ~LK_SHARE_NONZERO; 133 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 134 wakeup(lkp); 135 } 136 lkp->lk_sharecount = 0; 137 } else { 138 lkp->lk_sharecount -= decr; 139 } 140} 141 142static int 143acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime) 144{ 145 struct lock *lkp = *lkpp; 146 int error; 147 CTR3(KTR_LOCK, 148 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", 149 lkp, extflags, wanted); 150 151 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) 152 return EBUSY; 153 error = 0; 154 if ((lkp->lk_flags & wanted) != 0) 155 lock_profile_obtain_lock_failed(&lkp->lk_object, contested, waittime); 156 157 while ((lkp->lk_flags & wanted) != 0) { 158 CTR2(KTR_LOCK, 159 "acquire(): lkp == %p, lk_flags == 0x%x sleeping", 160 lkp, lkp->lk_flags); 161 lkp->lk_flags |= LK_WAIT_NONZERO; 162 lkp->lk_waitcount++; 163 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio, 164 lkp->lk_wmesg, 165 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 166 lkp->lk_waitcount--; 167 if (lkp->lk_waitcount == 0) 168 lkp->lk_flags &= ~LK_WAIT_NONZERO; 169 if (error) 170 break; 171 if (extflags & LK_SLEEPFAIL) { 172 error = ENOLCK; 173 break; 174 } 175 if (lkp->lk_newlock != NULL) { 176 mtx_lock(lkp->lk_newlock->lk_interlock); 177 mtx_unlock(lkp->lk_interlock); 178 if (lkp->lk_waitcount == 0) 179 wakeup((void *)(&lkp->lk_newlock)); 180 *lkpp = lkp = lkp->lk_newlock; 181 } 182 } 183 mtx_assert(lkp->lk_interlock, MA_OWNED); 184 return (error); 185} 186 187/* 188 * Set, change, or release a lock. 189 * 190 * Shared requests increment the shared count. Exclusive requests set the 191 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 192 * accepted shared locks and shared-to-exclusive upgrades to go away. 193 */ 194int 195_lockmgr(struct lock *lkp, u_int flags, struct mtx *interlkp, char *file, 196 int line) 197 198{ 199 struct thread *td; 200 int error; 201 int extflags, lockflags; 202 int contested = 0; 203 uint64_t waitstart = 0; 204 205 error = 0; 206 td = curthread; 207 208 if ((flags & LK_INTERNAL) == 0) 209 mtx_lock(lkp->lk_interlock); 210 CTR6(KTR_LOCK, 211 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, " 212 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder, 213 lkp->lk_exclusivecount, flags, td); 214#ifdef DEBUG_LOCKS 215 { 216 struct stack stack; /* XXX */ 217 stack_save(&stack); 218 CTRSTACK(KTR_LOCK, &stack, 0, 1); 219 } 220#endif 221 222 if (flags & LK_INTERLOCK) { 223 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED); 224 mtx_unlock(interlkp); 225 } 226 227 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0) 228 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, 229 &lkp->lk_interlock->lock_object, 230 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg); 231 232 if (panicstr != NULL) { 233 mtx_unlock(lkp->lk_interlock); 234 return (0); 235 } 236 if ((lkp->lk_flags & LK_NOSHARE) && 237 (flags & LK_TYPE_MASK) == LK_SHARED) { 238 flags &= ~LK_TYPE_MASK; 239 flags |= LK_EXCLUSIVE; 240 } 241 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 242 243 switch (flags & LK_TYPE_MASK) { 244 245 case LK_SHARED: 246 if (!LOCKMGR_TRYOP(extflags)) 247 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER, file, 248 line); 249 /* 250 * If we are not the exclusive lock holder, we have to block 251 * while there is an exclusive lock holder or while an 252 * exclusive lock request or upgrade request is in progress. 253 * 254 * However, if TDP_DEADLKTREAT is set, we override exclusive 255 * lock requests or upgrade requests ( but not the exclusive 256 * lock itself ). 257 */ 258 if (lkp->lk_lockholder != td) { 259 lockflags = LK_HAVE_EXCL; 260 if (!(td->td_pflags & TDP_DEADLKTREAT)) 261 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; 262 error = acquire(&lkp, extflags, lockflags, &contested, &waitstart); 263 if (error) 264 break; 265 sharelock(td, lkp, 1); 266 if (lkp->lk_sharecount == 1) 267 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 268 WITNESS_LOCK(&lkp->lk_object, LOCKMGR_TRYW(extflags), 269 file, line); 270 271#if defined(DEBUG_LOCKS) 272 stack_save(&lkp->lk_stack); 273#endif 274 break; 275 } 276 /* 277 * We hold an exclusive lock, so downgrade it to shared. 278 * An alternative would be to fail with EDEADLK. 279 */ 280 /* FALLTHROUGH downgrade */ 281 282 case LK_DOWNGRADE: 283 KASSERT(lkp->lk_lockholder == td && lkp->lk_exclusivecount != 0, 284 ("lockmgr: not holding exclusive lock " 285 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0", 286 lkp->lk_lockholder, td, lkp->lk_exclusivecount)); 287 sharelock(td, lkp, lkp->lk_exclusivecount); 288 WITNESS_DOWNGRADE(&lkp->lk_object, 0, file, line); 289 COUNT(td, -lkp->lk_exclusivecount); 290 lkp->lk_exclusivecount = 0; 291 lkp->lk_flags &= ~LK_HAVE_EXCL; 292 lkp->lk_lockholder = LK_NOPROC; 293 if (lkp->lk_waitcount) 294 wakeup((void *)lkp); 295 break; 296 297 case LK_UPGRADE: 298 /* 299 * Upgrade a shared lock to an exclusive one. If another 300 * shared lock has already requested an upgrade to an 301 * exclusive lock, our shared lock is released and an 302 * exclusive lock is requested (which will be granted 303 * after the upgrade). If we return an error, the file 304 * will always be unlocked. 305 */ 306 if (lkp->lk_lockholder == td) 307 panic("lockmgr: upgrade exclusive lock"); 308 if (lkp->lk_sharecount <= 0) 309 panic("lockmgr: upgrade without shared"); 310 shareunlock(td, lkp, 1); 311 if (lkp->lk_sharecount == 0) 312 lock_profile_release_lock(&lkp->lk_object); 313 /* 314 * If we are just polling, check to see if we will block. 315 */ 316 if ((extflags & LK_NOWAIT) && 317 ((lkp->lk_flags & LK_WANT_UPGRADE) || 318 lkp->lk_sharecount > 1)) { 319 error = EBUSY; 320 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 321 break; 322 } 323 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) { 324 /* 325 * We are first shared lock to request an upgrade, so 326 * request upgrade and wait for the shared count to 327 * drop to zero, then take exclusive lock. 328 */ 329 lkp->lk_flags |= LK_WANT_UPGRADE; 330 error = acquire(&lkp, extflags, LK_SHARE_NONZERO, &contested, &waitstart); 331 lkp->lk_flags &= ~LK_WANT_UPGRADE; 332 333 if (error) { 334 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO)) 335 wakeup((void *)lkp); 336 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 337 break; 338 } 339 if (lkp->lk_exclusivecount != 0) 340 panic("lockmgr: non-zero exclusive count"); 341 lkp->lk_flags |= LK_HAVE_EXCL; 342 lkp->lk_lockholder = td; 343 lkp->lk_exclusivecount = 1; 344 WITNESS_UPGRADE(&lkp->lk_object, LOP_EXCLUSIVE | 345 LOP_TRYLOCK, file, line); 346 COUNT(td, 1); 347 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 348#if defined(DEBUG_LOCKS) 349 stack_save(&lkp->lk_stack); 350#endif 351 break; 352 } 353 /* 354 * Someone else has requested upgrade. Release our shared 355 * lock, awaken upgrade requestor if we are the last shared 356 * lock, then request an exclusive lock. 357 */ 358 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 359 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 360 LK_WAIT_NONZERO) 361 wakeup((void *)lkp); 362 /* FALLTHROUGH exclusive request */ 363 364 case LK_EXCLUSIVE: 365 if (!LOCKMGR_TRYOP(extflags)) 366 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER | 367 LOP_EXCLUSIVE, file, line); 368 if (lkp->lk_lockholder == td) { 369 /* 370 * Recursive lock. 371 */ 372 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 373 panic("lockmgr: locking against myself"); 374 if ((extflags & LK_CANRECURSE) != 0) { 375 lkp->lk_exclusivecount++; 376 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 377 LOCKMGR_TRYW(extflags), file, line); 378 COUNT(td, 1); 379 break; 380 } 381 } 382 /* 383 * If we are just polling, check to see if we will sleep. 384 */ 385 if ((extflags & LK_NOWAIT) && 386 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) { 387 error = EBUSY; 388 break; 389 } 390 /* 391 * Try to acquire the want_exclusive flag. 392 */ 393 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL), &contested, &waitstart); 394 if (error) 395 break; 396 lkp->lk_flags |= LK_WANT_EXCL; 397 /* 398 * Wait for shared locks and upgrades to finish. 399 */ 400 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO, &contested, &waitstart); 401 lkp->lk_flags &= ~LK_WANT_EXCL; 402 if (error) { 403 if (lkp->lk_flags & LK_WAIT_NONZERO) 404 wakeup((void *)lkp); 405 break; 406 } 407 lkp->lk_flags |= LK_HAVE_EXCL; 408 lkp->lk_lockholder = td; 409 if (lkp->lk_exclusivecount != 0) 410 panic("lockmgr: non-zero exclusive count"); 411 lkp->lk_exclusivecount = 1; 412 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 413 LOCKMGR_TRYW(extflags), file, line); 414 COUNT(td, 1); 415 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 416#if defined(DEBUG_LOCKS) 417 stack_save(&lkp->lk_stack); 418#endif 419 break; 420 421 case LK_RELEASE: 422 if (lkp->lk_exclusivecount != 0) { 423 if (lkp->lk_lockholder != td && 424 lkp->lk_lockholder != LK_KERNPROC) { 425 panic("lockmgr: thread %p, not %s %p unlocking", 426 td, "exclusive lock holder", 427 lkp->lk_lockholder); 428 } 429 if (lkp->lk_lockholder != LK_KERNPROC) { 430 WITNESS_UNLOCK(&lkp->lk_object, LOP_EXCLUSIVE, 431 file, line); 432 COUNT(td, -1); 433 } 434 if (lkp->lk_exclusivecount == 1) { 435 lkp->lk_flags &= ~LK_HAVE_EXCL; 436 lkp->lk_lockholder = LK_NOPROC; 437 lkp->lk_exclusivecount = 0; 438 lock_profile_release_lock(&lkp->lk_object); 439 } else { 440 lkp->lk_exclusivecount--; 441 } 442 } else if (lkp->lk_flags & LK_SHARE_NONZERO) { 443 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 444 shareunlock(td, lkp, 1); 445 } else { 446 printf("lockmgr: thread %p unlocking unheld lock\n", 447 td); 448 kdb_backtrace(); 449 } 450 451 if (lkp->lk_flags & LK_WAIT_NONZERO) 452 wakeup((void *)lkp); 453 break; 454 455 case LK_DRAIN: 456 /* 457 * Check that we do not already hold the lock, as it can 458 * never drain if we do. Unfortunately, we have no way to 459 * check for holding a shared lock, but at least we can 460 * check for an exclusive one. 461 */ 462 if (!LOCKMGR_TRYOP(extflags)) 463 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER | 464 LOP_EXCLUSIVE, file, line); 465 if (lkp->lk_lockholder == td) 466 panic("lockmgr: draining against myself"); 467 468 error = acquiredrain(lkp, extflags); 469 if (error) 470 break; 471 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 472 lkp->lk_lockholder = td; 473 lkp->lk_exclusivecount = 1; 474 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 475 LOCKMGR_TRYW(extflags), file, line); 476 COUNT(td, 1); 477#if defined(DEBUG_LOCKS) 478 stack_save(&lkp->lk_stack); 479#endif 480 break; 481 482 default: 483 mtx_unlock(lkp->lk_interlock); 484 panic("lockmgr: unknown locktype request %d", 485 flags & LK_TYPE_MASK); 486 /* NOTREACHED */ 487 } 488 if ((lkp->lk_flags & LK_WAITDRAIN) && 489 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 490 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 491 lkp->lk_flags &= ~LK_WAITDRAIN; 492 wakeup((void *)&lkp->lk_flags); 493 } 494 mtx_unlock(lkp->lk_interlock); 495 return (error); 496} 497 498static int 499acquiredrain(struct lock *lkp, int extflags) { 500 int error; 501 502 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 503 return EBUSY; 504 } 505 while (lkp->lk_flags & LK_ALL) { 506 lkp->lk_flags |= LK_WAITDRAIN; 507 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio, 508 lkp->lk_wmesg, 509 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 510 if (error) 511 return error; 512 if (extflags & LK_SLEEPFAIL) { 513 return ENOLCK; 514 } 515 } 516 return 0; 517} 518 519/* 520 * Initialize a lock; required before use. 521 */ 522void 523lockinit(lkp, prio, wmesg, timo, flags) 524 struct lock *lkp; 525 int prio; 526 const char *wmesg; 527 int timo; 528 int flags; 529{ 530 int iflags; 531 532 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", " 533 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags); 534 535 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder); 536 lkp->lk_flags = (flags & LK_EXTFLG_MASK) & ~(LK_NOWITNESS | LK_NODUP); 537 lkp->lk_sharecount = 0; 538 lkp->lk_waitcount = 0; 539 lkp->lk_exclusivecount = 0; 540 lkp->lk_prio = prio; 541 lkp->lk_timo = timo; 542 lkp->lk_lockholder = LK_NOPROC; 543 lkp->lk_newlock = NULL; 544 iflags = LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE; 545 if (!(flags & LK_NODUP)) 546 iflags |= LO_DUPOK; 547 if (!(flags & LK_NOWITNESS)) 548 iflags |= LO_WITNESS; 549#ifdef DEBUG_LOCKS 550 stack_zero(&lkp->lk_stack); 551#endif 552 lock_init(&lkp->lk_object, &lock_class_lockmgr, wmesg, NULL, iflags); 553} 554 555/* 556 * Destroy a lock. 557 */ 558void 559lockdestroy(lkp) 560 struct lock *lkp; 561{ 562 563 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", 564 lkp, lkp->lk_wmesg); 565 lock_destroy(&lkp->lk_object); 566} 567 568/* 569 * Disown the lockmgr. 570 */ 571void 572_lockmgr_disown(struct lock *lkp, const char *file, int line) 573{ 574 struct thread *td; 575 576 td = curthread; 577 KASSERT(panicstr != NULL || lkp->lk_exclusivecount, 578 ("%s: %p lockmgr must be exclusively locked", __func__, lkp)); 579 KASSERT(panicstr != NULL || lkp->lk_lockholder == td || 580 lkp->lk_lockholder == LK_KERNPROC, 581 ("%s: %p lockmgr must be locked by curthread (%p)", __func__, lkp, 582 td)); 583 584 /* 585 * Drop the lock reference and switch the owner. This will result 586 * in an atomic operation like td_lock is only accessed by curthread 587 * and lk_lockholder only needs one write. Note also that the lock 588 * owner can be alredy KERNPROC, so in that case just skip the 589 * decrement. 590 */ 591 if (lkp->lk_lockholder == td) { 592 WITNESS_UNLOCK(&lkp->lk_object, LOP_EXCLUSIVE, file, line); 593 td->td_locks--; 594 } 595 lkp->lk_lockholder = LK_KERNPROC; 596} 597 598/* 599 * Determine the status of a lock. 600 */ 601int 602lockstatus(lkp, td) 603 struct lock *lkp; 604 struct thread *td; 605{ 606 int lock_type = 0; 607 int interlocked; 608 609 KASSERT(td == NULL || td == curthread, 610 ("%s: thread passed argument (%p) is not valid", __func__, td)); 611 612 if (!kdb_active) { 613 interlocked = 1; 614 mtx_lock(lkp->lk_interlock); 615 } else 616 interlocked = 0; 617 if (lkp->lk_exclusivecount != 0) { 618 if (td == NULL || lkp->lk_lockholder == td) 619 lock_type = LK_EXCLUSIVE; 620 else 621 lock_type = LK_EXCLOTHER; 622 } else if (lkp->lk_sharecount != 0) 623 lock_type = LK_SHARED; 624 if (interlocked) 625 mtx_unlock(lkp->lk_interlock); 626 return (lock_type); 627} 628 629/* 630 * Determine the number of waiters on a lock. 631 */ 632int 633lockwaiters(lkp) 634 struct lock *lkp; 635{ 636 int count; 637 638 mtx_lock(lkp->lk_interlock); 639 count = lkp->lk_waitcount; 640 mtx_unlock(lkp->lk_interlock); 641 return (count); 642} 643 644/* 645 * Print out information about state of a lock. Used by VOP_PRINT 646 * routines to display status about contained locks. 647 */ 648void 649lockmgr_printinfo(lkp) 650 struct lock *lkp; 651{ 652 653 if (lkp->lk_sharecount) 654 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 655 lkp->lk_sharecount); 656 else if (lkp->lk_flags & LK_HAVE_EXCL) 657 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)", 658 lkp->lk_wmesg, lkp->lk_exclusivecount, 659 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); 660 if (lkp->lk_waitcount > 0) 661 printf(" with %d pending", lkp->lk_waitcount); 662#ifdef DEBUG_LOCKS 663 stack_print_ddb(&lkp->lk_stack); 664#endif 665} 666 667#ifdef DDB 668/* 669 * Check to see if a thread that is blocked on a sleep queue is actually 670 * blocked on a 'struct lock'. If so, output some details and return true. 671 * If the lock has an exclusive owner, return that in *ownerp. 672 */ 673int 674lockmgr_chain(struct thread *td, struct thread **ownerp) 675{ 676 struct lock *lkp; 677 678 lkp = td->td_wchan; 679 680 /* Simple test to see if wchan points to a lockmgr lock. */ 681 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 682 lkp->lk_wmesg == td->td_wmesg) 683 goto ok; 684 685 /* 686 * If this thread is doing a DRAIN, then it would be asleep on 687 * &lkp->lk_flags rather than lkp. 688 */ 689 lkp = (struct lock *)((char *)td->td_wchan - 690 offsetof(struct lock, lk_flags)); 691 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 692 lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN)) 693 goto ok; 694 695 /* Doen't seem to be a lockmgr lock. */ 696 return (0); 697 698ok: 699 /* Ok, we think we have a lockmgr lock, so output some details. */ 700 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); 701 if (lkp->lk_sharecount) { 702 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 703 *ownerp = NULL; 704 } else { 705 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); 706 *ownerp = lkp->lk_lockholder; 707 } 708 return (1); 709} 710 711void 712db_show_lockmgr(struct lock_object *lock) 713{ 714 struct thread *td; 715 struct lock *lkp; 716 717 lkp = (struct lock *)lock; 718 719 db_printf(" lock type: %s\n", lkp->lk_wmesg); 720 db_printf(" state: "); 721 if (lkp->lk_sharecount) 722 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 723 else if (lkp->lk_flags & LK_HAVE_EXCL) { 724 td = lkp->lk_lockholder; 725 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); 726 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, 727 td->td_proc->p_pid, td->td_name); 728 } else 729 db_printf("UNLOCKED\n"); 730 if (lkp->lk_waitcount > 0) 731 db_printf(" waiters: %d\n", lkp->lk_waitcount); 732} 733#endif 734