kern_lock.c revision 176249
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 176249 2008-02-13 20:44:19Z 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#define LOCKMGR_UNHELD(x) (((x) & (LK_HAVE_EXCL | LK_SHARE_NONZERO)) == 0) 66#define LOCKMGR_NOTOWNER(td) ((td) != curthread && (td) != LK_KERNPROC) 67 68static void assert_lockmgr(struct lock_object *lock, int what); 69#ifdef DDB 70#include <ddb/ddb.h> 71static void db_show_lockmgr(struct lock_object *lock); 72#endif 73static void lock_lockmgr(struct lock_object *lock, int how); 74static int unlock_lockmgr(struct lock_object *lock); 75 76struct lock_class lock_class_lockmgr = { 77 .lc_name = "lockmgr", 78 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 79 .lc_assert = assert_lockmgr, 80#ifdef DDB 81 .lc_ddb_show = db_show_lockmgr, 82#endif 83 .lc_lock = lock_lockmgr, 84 .lc_unlock = unlock_lockmgr, 85}; 86 87#ifndef INVARIANTS 88#define _lockmgr_assert(lkp, what, file, line) 89#endif 90 91/* 92 * Locking primitives implementation. 93 * Locks provide shared/exclusive sychronization. 94 */ 95 96void 97assert_lockmgr(struct lock_object *lock, int what) 98{ 99 100 panic("lockmgr locks do not support assertions"); 101} 102 103void 104lock_lockmgr(struct lock_object *lock, int how) 105{ 106 107 panic("lockmgr locks do not support sleep interlocking"); 108} 109 110int 111unlock_lockmgr(struct lock_object *lock) 112{ 113 114 panic("lockmgr locks do not support sleep interlocking"); 115} 116 117#define COUNT(td, x) ((td)->td_locks += (x)) 118#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 119 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 120 121static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime); 122static int acquiredrain(struct lock *lkp, int extflags) ; 123 124static __inline void 125sharelock(struct thread *td, struct lock *lkp, int incr) { 126 lkp->lk_flags |= LK_SHARE_NONZERO; 127 lkp->lk_sharecount += incr; 128 COUNT(td, incr); 129} 130 131static __inline void 132shareunlock(struct thread *td, struct lock *lkp, int decr) { 133 134 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 135 136 COUNT(td, -decr); 137 if (lkp->lk_sharecount == decr) { 138 lkp->lk_flags &= ~LK_SHARE_NONZERO; 139 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 140 wakeup(lkp); 141 } 142 lkp->lk_sharecount = 0; 143 } else { 144 lkp->lk_sharecount -= decr; 145 } 146} 147 148static int 149acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime) 150{ 151 struct lock *lkp = *lkpp; 152 int error; 153 CTR3(KTR_LOCK, 154 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", 155 lkp, extflags, wanted); 156 157 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) 158 return EBUSY; 159 error = 0; 160 if ((lkp->lk_flags & wanted) != 0) 161 lock_profile_obtain_lock_failed(&lkp->lk_object, contested, waittime); 162 163 while ((lkp->lk_flags & wanted) != 0) { 164 CTR2(KTR_LOCK, 165 "acquire(): lkp == %p, lk_flags == 0x%x sleeping", 166 lkp, lkp->lk_flags); 167 lkp->lk_flags |= LK_WAIT_NONZERO; 168 lkp->lk_waitcount++; 169 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio, 170 lkp->lk_wmesg, 171 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 172 lkp->lk_waitcount--; 173 if (lkp->lk_waitcount == 0) 174 lkp->lk_flags &= ~LK_WAIT_NONZERO; 175 if (error) 176 break; 177 if (extflags & LK_SLEEPFAIL) { 178 error = ENOLCK; 179 break; 180 } 181 if (lkp->lk_newlock != NULL) { 182 mtx_lock(lkp->lk_newlock->lk_interlock); 183 mtx_unlock(lkp->lk_interlock); 184 if (lkp->lk_waitcount == 0) 185 wakeup((void *)(&lkp->lk_newlock)); 186 *lkpp = lkp = lkp->lk_newlock; 187 } 188 } 189 mtx_assert(lkp->lk_interlock, MA_OWNED); 190 return (error); 191} 192 193/* 194 * Set, change, or release a lock. 195 * 196 * Shared requests increment the shared count. Exclusive requests set the 197 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 198 * accepted shared locks and shared-to-exclusive upgrades to go away. 199 */ 200int 201_lockmgr(struct lock *lkp, u_int flags, struct mtx *interlkp, char *file, 202 int line) 203 204{ 205 struct thread *td; 206 int error; 207 int extflags, lockflags; 208 int contested = 0; 209 uint64_t waitstart = 0; 210 211 error = 0; 212 td = curthread; 213 214#ifdef INVARIANTS 215 if (lkp->lk_flags & LK_DESTROYED) { 216 if (flags & LK_INTERLOCK) 217 mtx_unlock(interlkp); 218 if (panicstr != NULL) 219 return (0); 220 panic("%s: %p lockmgr is destroyed", __func__, lkp); 221 } 222#endif 223 if ((flags & LK_INTERNAL) == 0) 224 mtx_lock(lkp->lk_interlock); 225 CTR6(KTR_LOCK, 226 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, " 227 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder, 228 lkp->lk_exclusivecount, flags, td); 229#ifdef DEBUG_LOCKS 230 { 231 struct stack stack; /* XXX */ 232 stack_save(&stack); 233 CTRSTACK(KTR_LOCK, &stack, 0, 1); 234 } 235#endif 236 237 if (flags & LK_INTERLOCK) { 238 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED); 239 mtx_unlock(interlkp); 240 } 241 242 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0) 243 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, 244 &lkp->lk_interlock->lock_object, 245 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg); 246 247 if (panicstr != NULL) { 248 mtx_unlock(lkp->lk_interlock); 249 return (0); 250 } 251 if ((lkp->lk_flags & LK_NOSHARE) && 252 (flags & LK_TYPE_MASK) == LK_SHARED) { 253 flags &= ~LK_TYPE_MASK; 254 flags |= LK_EXCLUSIVE; 255 } 256 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 257 258 switch (flags & LK_TYPE_MASK) { 259 260 case LK_SHARED: 261 if (!LOCKMGR_TRYOP(extflags)) 262 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER, file, 263 line); 264 /* 265 * If we are not the exclusive lock holder, we have to block 266 * while there is an exclusive lock holder or while an 267 * exclusive lock request or upgrade request is in progress. 268 * 269 * However, if TDP_DEADLKTREAT is set, we override exclusive 270 * lock requests or upgrade requests ( but not the exclusive 271 * lock itself ). 272 */ 273 if (lkp->lk_lockholder != td) { 274 lockflags = LK_HAVE_EXCL; 275 if (!(td->td_pflags & TDP_DEADLKTREAT)) 276 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; 277 error = acquire(&lkp, extflags, lockflags, &contested, &waitstart); 278 if (error) 279 break; 280 sharelock(td, lkp, 1); 281 if (lkp->lk_sharecount == 1) 282 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 283 WITNESS_LOCK(&lkp->lk_object, LOCKMGR_TRYW(extflags), 284 file, line); 285 286#if defined(DEBUG_LOCKS) 287 stack_save(&lkp->lk_stack); 288#endif 289 break; 290 } 291 /* 292 * We hold an exclusive lock, so downgrade it to shared. 293 * An alternative would be to fail with EDEADLK. 294 */ 295 /* FALLTHROUGH downgrade */ 296 297 case LK_DOWNGRADE: 298 _lockmgr_assert(lkp, KA_XLOCKED, file, line); 299 sharelock(td, lkp, lkp->lk_exclusivecount); 300 WITNESS_DOWNGRADE(&lkp->lk_object, 0, file, line); 301 COUNT(td, -lkp->lk_exclusivecount); 302 lkp->lk_exclusivecount = 0; 303 lkp->lk_flags &= ~LK_HAVE_EXCL; 304 lkp->lk_lockholder = LK_NOPROC; 305 if (lkp->lk_waitcount) 306 wakeup((void *)lkp); 307 break; 308 309 case LK_UPGRADE: 310 /* 311 * Upgrade a shared lock to an exclusive one. If another 312 * shared lock has already requested an upgrade to an 313 * exclusive lock, our shared lock is released and an 314 * exclusive lock is requested (which will be granted 315 * after the upgrade). If we return an error, the file 316 * will always be unlocked. 317 */ 318 _lockmgr_assert(lkp, KA_SLOCKED, file, line); 319 shareunlock(td, lkp, 1); 320 if (lkp->lk_sharecount == 0) 321 lock_profile_release_lock(&lkp->lk_object); 322 /* 323 * If we are just polling, check to see if we will block. 324 */ 325 if ((extflags & LK_NOWAIT) && 326 ((lkp->lk_flags & LK_WANT_UPGRADE) || 327 lkp->lk_sharecount > 1)) { 328 error = EBUSY; 329 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 330 break; 331 } 332 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) { 333 /* 334 * We are first shared lock to request an upgrade, so 335 * request upgrade and wait for the shared count to 336 * drop to zero, then take exclusive lock. 337 */ 338 lkp->lk_flags |= LK_WANT_UPGRADE; 339 error = acquire(&lkp, extflags, LK_SHARE_NONZERO, &contested, &waitstart); 340 lkp->lk_flags &= ~LK_WANT_UPGRADE; 341 342 if (error) { 343 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO)) 344 wakeup((void *)lkp); 345 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 346 break; 347 } 348 if (lkp->lk_exclusivecount != 0) 349 panic("lockmgr: non-zero exclusive count"); 350 lkp->lk_flags |= LK_HAVE_EXCL; 351 lkp->lk_lockholder = td; 352 lkp->lk_exclusivecount = 1; 353 WITNESS_UPGRADE(&lkp->lk_object, LOP_EXCLUSIVE | 354 LOP_TRYLOCK, file, line); 355 COUNT(td, 1); 356 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 357#if defined(DEBUG_LOCKS) 358 stack_save(&lkp->lk_stack); 359#endif 360 break; 361 } 362 /* 363 * Someone else has requested upgrade. Release our shared 364 * lock, awaken upgrade requestor if we are the last shared 365 * lock, then request an exclusive lock. 366 */ 367 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 368 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 369 LK_WAIT_NONZERO) 370 wakeup((void *)lkp); 371 /* FALLTHROUGH exclusive request */ 372 373 case LK_EXCLUSIVE: 374 if (!LOCKMGR_TRYOP(extflags)) 375 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER | 376 LOP_EXCLUSIVE, file, line); 377 if (lkp->lk_lockholder == td) { 378 /* 379 * Recursive lock. 380 */ 381 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 382 panic("lockmgr: locking against myself"); 383 if ((extflags & LK_CANRECURSE) != 0) { 384 lkp->lk_exclusivecount++; 385 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 386 LOCKMGR_TRYW(extflags), file, line); 387 COUNT(td, 1); 388 break; 389 } 390 } 391 /* 392 * If we are just polling, check to see if we will sleep. 393 */ 394 if ((extflags & LK_NOWAIT) && 395 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) { 396 error = EBUSY; 397 break; 398 } 399 /* 400 * Try to acquire the want_exclusive flag. 401 */ 402 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL), &contested, &waitstart); 403 if (error) 404 break; 405 lkp->lk_flags |= LK_WANT_EXCL; 406 /* 407 * Wait for shared locks and upgrades to finish. 408 */ 409 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO, &contested, &waitstart); 410 lkp->lk_flags &= ~LK_WANT_EXCL; 411 if (error) { 412 if (lkp->lk_flags & LK_WAIT_NONZERO) 413 wakeup((void *)lkp); 414 break; 415 } 416 lkp->lk_flags |= LK_HAVE_EXCL; 417 lkp->lk_lockholder = td; 418 if (lkp->lk_exclusivecount != 0) 419 panic("lockmgr: non-zero exclusive count"); 420 lkp->lk_exclusivecount = 1; 421 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 422 LOCKMGR_TRYW(extflags), file, line); 423 COUNT(td, 1); 424 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 425#if defined(DEBUG_LOCKS) 426 stack_save(&lkp->lk_stack); 427#endif 428 break; 429 430 case LK_RELEASE: 431 _lockmgr_assert(lkp, KA_LOCKED, file, line); 432 if (lkp->lk_exclusivecount != 0) { 433 if (lkp->lk_lockholder != LK_KERNPROC) { 434 WITNESS_UNLOCK(&lkp->lk_object, LOP_EXCLUSIVE, 435 file, line); 436 COUNT(td, -1); 437 } 438 if (lkp->lk_exclusivecount-- == 1) { 439 lkp->lk_flags &= ~LK_HAVE_EXCL; 440 lkp->lk_lockholder = LK_NOPROC; 441 lock_profile_release_lock(&lkp->lk_object); 442 } 443 } else if (lkp->lk_flags & LK_SHARE_NONZERO) { 444 WITNESS_UNLOCK(&lkp->lk_object, 0, file, line); 445 shareunlock(td, lkp, 1); 446 } 447 448 if (lkp->lk_flags & LK_WAIT_NONZERO) 449 wakeup((void *)lkp); 450 break; 451 452 case LK_DRAIN: 453 /* 454 * Check that we do not already hold the lock, as it can 455 * never drain if we do. Unfortunately, we have no way to 456 * check for holding a shared lock, but at least we can 457 * check for an exclusive one. 458 */ 459 if (!LOCKMGR_TRYOP(extflags)) 460 WITNESS_CHECKORDER(&lkp->lk_object, LOP_NEWORDER | 461 LOP_EXCLUSIVE, file, line); 462 if (lkp->lk_lockholder == td) 463 panic("lockmgr: draining against myself"); 464 465 error = acquiredrain(lkp, extflags); 466 if (error) 467 break; 468 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 469 lkp->lk_lockholder = td; 470 lkp->lk_exclusivecount = 1; 471 WITNESS_LOCK(&lkp->lk_object, LOP_EXCLUSIVE | 472 LOCKMGR_TRYW(extflags), file, line); 473 COUNT(td, 1); 474#if defined(DEBUG_LOCKS) 475 stack_save(&lkp->lk_stack); 476#endif 477 break; 478 479 default: 480 mtx_unlock(lkp->lk_interlock); 481 panic("lockmgr: unknown locktype request %d", 482 flags & LK_TYPE_MASK); 483 /* NOTREACHED */ 484 } 485 if ((lkp->lk_flags & LK_WAITDRAIN) && 486 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 487 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 488 lkp->lk_flags &= ~LK_WAITDRAIN; 489 wakeup((void *)&lkp->lk_flags); 490 } 491 mtx_unlock(lkp->lk_interlock); 492 return (error); 493} 494 495static int 496acquiredrain(struct lock *lkp, int extflags) { 497 int error; 498 499 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 500 return EBUSY; 501 } 502 while (lkp->lk_flags & LK_ALL) { 503 lkp->lk_flags |= LK_WAITDRAIN; 504 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio, 505 lkp->lk_wmesg, 506 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 507 if (error) 508 return error; 509 if (extflags & LK_SLEEPFAIL) { 510 return ENOLCK; 511 } 512 } 513 return 0; 514} 515 516/* 517 * Initialize a lock; required before use. 518 */ 519void 520lockinit(lkp, prio, wmesg, timo, flags) 521 struct lock *lkp; 522 int prio; 523 const char *wmesg; 524 int timo; 525 int flags; 526{ 527 int iflags; 528 529 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", " 530 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags); 531 532 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder); 533 lkp->lk_flags = (flags & LK_EXTFLG_MASK) & ~(LK_NOWITNESS | LK_NODUP); 534 lkp->lk_sharecount = 0; 535 lkp->lk_waitcount = 0; 536 lkp->lk_exclusivecount = 0; 537 lkp->lk_prio = prio; 538 lkp->lk_timo = timo; 539 lkp->lk_lockholder = LK_NOPROC; 540 lkp->lk_newlock = NULL; 541 iflags = LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE; 542 if (!(flags & LK_NODUP)) 543 iflags |= LO_DUPOK; 544 if (!(flags & LK_NOWITNESS)) 545 iflags |= LO_WITNESS; 546#ifdef DEBUG_LOCKS 547 stack_zero(&lkp->lk_stack); 548#endif 549 lock_init(&lkp->lk_object, &lock_class_lockmgr, wmesg, NULL, iflags); 550} 551 552/* 553 * Destroy a lock. 554 */ 555void 556lockdestroy(lkp) 557 struct lock *lkp; 558{ 559 560 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", 561 lkp, lkp->lk_wmesg); 562 KASSERT((lkp->lk_flags & (LK_HAVE_EXCL | LK_SHARE_NONZERO)) == 0, 563 ("lockmgr still held")); 564 KASSERT(lkp->lk_exclusivecount == 0, ("lockmgr still recursed")); 565 lkp->lk_flags = LK_DESTROYED; 566 lock_destroy(&lkp->lk_object); 567} 568 569/* 570 * Disown the lockmgr. 571 */ 572void 573_lockmgr_disown(struct lock *lkp, const char *file, int line) 574{ 575 struct thread *td; 576 577 td = curthread; 578 KASSERT(panicstr != NULL || (lkp->lk_flags & LK_DESTROYED) == 0, 579 ("%s: %p lockmgr is destroyed", __func__, lkp)); 580 _lockmgr_assert(lkp, KA_XLOCKED | KA_NOTRECURSED, file, line); 581 582 /* 583 * Drop the lock reference and switch the owner. This will result 584 * in an atomic operation like td_lock is only accessed by curthread 585 * and lk_lockholder only needs one write. Note also that the lock 586 * owner can be alredy KERNPROC, so in that case just skip the 587 * decrement. 588 */ 589 if (lkp->lk_lockholder == td) { 590 WITNESS_UNLOCK(&lkp->lk_object, LOP_EXCLUSIVE, file, line); 591 td->td_locks--; 592 } 593 lkp->lk_lockholder = LK_KERNPROC; 594} 595 596/* 597 * Determine the status of a lock. 598 */ 599int 600lockstatus(lkp, td) 601 struct lock *lkp; 602 struct thread *td; 603{ 604 int lock_type = 0; 605 int interlocked; 606 607 KASSERT(td == curthread, 608 ("%s: thread passed argument (%p) is not valid", __func__, td)); 609 KASSERT((lkp->lk_flags & LK_DESTROYED) == 0, 610 ("%s: %p lockmgr is destroyed", __func__, lkp)); 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 (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 KASSERT((lkp->lk_flags & LK_DESTROYED) == 0, 639 ("%s: %p lockmgr is destroyed", __func__, lkp)); 640 mtx_lock(lkp->lk_interlock); 641 count = lkp->lk_waitcount; 642 mtx_unlock(lkp->lk_interlock); 643 return (count); 644} 645 646/* 647 * Print out information about state of a lock. Used by VOP_PRINT 648 * routines to display status about contained locks. 649 */ 650void 651lockmgr_printinfo(lkp) 652 struct lock *lkp; 653{ 654 655 if (lkp->lk_sharecount) 656 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 657 lkp->lk_sharecount); 658 else if (lkp->lk_flags & LK_HAVE_EXCL) 659 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)", 660 lkp->lk_wmesg, lkp->lk_exclusivecount, 661 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); 662 if (lkp->lk_waitcount > 0) 663 printf(" with %d pending", lkp->lk_waitcount); 664#ifdef DEBUG_LOCKS 665 stack_print_ddb(&lkp->lk_stack); 666#endif 667} 668 669#ifdef INVARIANT_SUPPORT 670#ifndef INVARIANTS 671#undef _lockmgr_assert 672#endif 673 674void 675_lockmgr_assert(struct lock *lkp, int what, const char *file, int line) 676{ 677 struct thread *td; 678 u_int x; 679 int slocked = 0; 680 681 x = lkp->lk_flags; 682 td = lkp->lk_lockholder; 683 if (panicstr != NULL) 684 return; 685 switch (what) { 686 case KA_SLOCKED: 687 case KA_SLOCKED | KA_NOTRECURSED: 688 case KA_SLOCKED | KA_RECURSED: 689 slocked = 1; 690 case KA_LOCKED: 691 case KA_LOCKED | KA_NOTRECURSED: 692 case KA_LOCKED | KA_RECURSED: 693#ifdef WITNESS 694 /* 695 * We cannot trust WITNESS if the lock is held in 696 * exclusive mode and a call to lockmgr_disown() happened. 697 * Workaround this skipping the check if the lock is 698 * held in exclusive mode even for the KA_LOCKED case. 699 */ 700 if (slocked || (x & LK_HAVE_EXCL) == 0) { 701 witness_assert(&lkp->lk_object, what, file, line); 702 break; 703 } 704#endif 705 if (LOCKMGR_UNHELD(x) || ((x & LK_SHARE_NONZERO) == 0 && 706 (slocked || LOCKMGR_NOTOWNER(td)))) 707 panic("Lock %s not %slocked @ %s:%d\n", 708 lkp->lk_object.lo_name, slocked ? "share " : "", 709 file, line); 710 if ((x & LK_SHARE_NONZERO) == 0) { 711 if (lockmgr_recursed(lkp)) { 712 if (what & KA_NOTRECURSED) 713 panic("Lock %s recursed @ %s:%d\n", 714 lkp->lk_object.lo_name, file, line); 715 } else if (what & KA_RECURSED) 716 panic("Lock %s not recursed @ %s:%d\n", 717 lkp->lk_object.lo_name, file, line); 718 } 719 break; 720 case KA_XLOCKED: 721 case KA_XLOCKED | KA_NOTRECURSED: 722 case KA_XLOCKED | KA_RECURSED: 723 if ((x & LK_HAVE_EXCL) == 0 || LOCKMGR_NOTOWNER(td)) 724 panic("Lock %s not exclusively locked @ %s:%d\n", 725 lkp->lk_object.lo_name, file, line); 726 if (lockmgr_recursed(lkp)) { 727 if (what & KA_NOTRECURSED) 728 panic("Lock %s recursed @ %s:%d\n", 729 lkp->lk_object.lo_name, file, line); 730 } else if (what & KA_RECURSED) 731 panic("Lock %s not recursed @ %s:%d\n", 732 lkp->lk_object.lo_name, file, line); 733 break; 734 case KA_UNLOCKED: 735 if (td == curthread || td == LK_KERNPROC) 736 panic("Lock %s exclusively locked @ %s:%d\n", 737 lkp->lk_object.lo_name, file, line); 738 break; 739 case KA_HELD: 740 case KA_UNHELD: 741 if (LOCKMGR_UNHELD(x)) { 742 if (what & KA_HELD) 743 panic("Lock %s not locked by anyone @ %s:%d\n", 744 lkp->lk_object.lo_name, file, line); 745 } else if (what & KA_UNHELD) 746 panic("Lock %s locked by someone @ %s:%d\n", 747 lkp->lk_object.lo_name, file, line); 748 break; 749 default: 750 panic("Unknown lockmgr lock assertion: 0x%x @ %s:%d", what, 751 file, line); 752 } 753} 754#endif /* INVARIANT_SUPPORT */ 755 756#ifdef DDB 757/* 758 * Check to see if a thread that is blocked on a sleep queue is actually 759 * blocked on a 'struct lock'. If so, output some details and return true. 760 * If the lock has an exclusive owner, return that in *ownerp. 761 */ 762int 763lockmgr_chain(struct thread *td, struct thread **ownerp) 764{ 765 struct lock *lkp; 766 767 lkp = td->td_wchan; 768 769 /* Simple test to see if wchan points to a lockmgr lock. */ 770 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 771 lkp->lk_wmesg == td->td_wmesg) 772 goto ok; 773 774 /* 775 * If this thread is doing a DRAIN, then it would be asleep on 776 * &lkp->lk_flags rather than lkp. 777 */ 778 lkp = (struct lock *)((char *)td->td_wchan - 779 offsetof(struct lock, lk_flags)); 780 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 781 lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN)) 782 goto ok; 783 784 /* Doen't seem to be a lockmgr lock. */ 785 return (0); 786 787ok: 788 /* Ok, we think we have a lockmgr lock, so output some details. */ 789 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); 790 if (lkp->lk_sharecount) { 791 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 792 *ownerp = NULL; 793 } else { 794 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); 795 *ownerp = lkp->lk_lockholder; 796 } 797 return (1); 798} 799 800void 801db_show_lockmgr(struct lock_object *lock) 802{ 803 struct thread *td; 804 struct lock *lkp; 805 806 lkp = (struct lock *)lock; 807 808 db_printf(" lock type: %s\n", lkp->lk_wmesg); 809 db_printf(" state: "); 810 if (lkp->lk_sharecount) 811 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 812 else if (lkp->lk_flags & LK_HAVE_EXCL) { 813 td = lkp->lk_lockholder; 814 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); 815 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, 816 td->td_proc->p_pid, td->td_name); 817 } else 818 db_printf("UNLOCKED\n"); 819 if (lkp->lk_waitcount > 0) 820 db_printf(" waiters: %d\n", lkp->lk_waitcount); 821} 822#endif 823