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("$FreeBSD$"); 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 static void assert_lockmgr(struct lock_object *lock, int what); 64 #ifdef DDB 65 #include <ddb/ddb.h> 66 static void db_show_lockmgr(struct lock_object *lock); 67 #endif 68 static void lock_lockmgr(struct lock_object *lock, int how); 69 static int unlock_lockmgr(struct lock_object *lock); 70 71 struct lock_class lock_class_lockmgr = { 72 .lc_name = "lockmgr", 73 .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 74 .lc_assert = assert_lockmgr, 75 #ifdef DDB 76 .lc_ddb_show = db_show_lockmgr, 77 #endif 78 .lc_lock = lock_lockmgr, 79 .lc_unlock = unlock_lockmgr, 80 }; 81 82 /* 83 * Locking primitives implementation. 84 * Locks provide shared/exclusive sychronization. 85 */ 86 87 void 88 assert_lockmgr(struct lock_object *lock, int what) 89 { 90 91 panic("lockmgr locks do not support assertions"); 92 } 93 94 void 95 lock_lockmgr(struct lock_object *lock, int how) 96 { 97 98 panic("lockmgr locks do not support sleep interlocking"); 99 } 100 101 int 102 unlock_lockmgr(struct lock_object *lock) 103 { 104 105 panic("lockmgr locks do not support sleep interlocking"); 106 } 107 108 #define COUNT(td, x) if ((td)) (td)->td_locks += (x) 109 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 110 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 111 112 static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime); 113 static int acquiredrain(struct lock *lkp, int extflags) ; 114 115 static __inline void 116 sharelock(struct thread *td, struct lock *lkp, int incr) { 117 lkp->lk_flags |= LK_SHARE_NONZERO; 118 lkp->lk_sharecount += incr; 119 COUNT(td, incr); 120 } 121 122 static __inline void 123 shareunlock(struct thread *td, struct lock *lkp, int decr) { 124 125 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 126 127 COUNT(td, -decr); 128 if (lkp->lk_sharecount == decr) { 129 lkp->lk_flags &= ~LK_SHARE_NONZERO; 130 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 131 wakeup(lkp); 132 } 133 lkp->lk_sharecount = 0; 134 } else { 135 lkp->lk_sharecount -= decr; 136 } 137 } 138 139 static int 140 acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime) 141 { 142 struct lock *lkp = *lkpp; 143 int error; 144 CTR3(KTR_LOCK, 145 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", 146 lkp, extflags, wanted); 147 148 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) 149 return EBUSY; 150 error = 0; 151 if ((lkp->lk_flags & wanted) != 0) 152 lock_profile_obtain_lock_failed(&lkp->lk_object, contested, waittime); 153 154 while ((lkp->lk_flags & wanted) != 0) { 155 CTR2(KTR_LOCK, 156 "acquire(): lkp == %p, lk_flags == 0x%x sleeping", 157 lkp, lkp->lk_flags); 158 lkp->lk_flags |= LK_WAIT_NONZERO; 159 lkp->lk_waitcount++; 160 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio, 161 lkp->lk_wmesg, 162 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 163 lkp->lk_waitcount--; 164 if (lkp->lk_waitcount == 0) 165 lkp->lk_flags &= ~LK_WAIT_NONZERO; 166 if (error) 167 break; 168 if (extflags & LK_SLEEPFAIL) { 169 error = ENOLCK; 170 break; 171 } 172 if (lkp->lk_newlock != NULL) { 173 mtx_lock(lkp->lk_newlock->lk_interlock); 174 mtx_unlock(lkp->lk_interlock); 175 if (lkp->lk_waitcount == 0) 176 wakeup((void *)(&lkp->lk_newlock)); 177 *lkpp = lkp = lkp->lk_newlock; 178 } 179 } 180 mtx_assert(lkp->lk_interlock, MA_OWNED); 181 return (error); 182 } 183 184 /* 185 * Set, change, or release a lock. 186 * 187 * Shared requests increment the shared count. Exclusive requests set the 188 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 189 * accepted shared locks and shared-to-exclusive upgrades to go away. 190 */ 191 int 192 _lockmgr(struct lock *lkp, u_int flags, struct mtx *interlkp, 193 struct thread *td, char *file, int line) 194 195 { 196 int error; 197 struct thread *thr; 198 int extflags, lockflags; 199 int contested = 0; 200 uint64_t waitstart = 0; 201 202 error = 0; 203 if (td == NULL) 204 thr = LK_KERNPROC; 205 else 206 thr = td; 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 /* 247 * If we are not the exclusive lock holder, we have to block 248 * while there is an exclusive lock holder or while an 249 * exclusive lock request or upgrade request is in progress. 250 * 251 * However, if TDP_DEADLKTREAT is set, we override exclusive 252 * lock requests or upgrade requests ( but not the exclusive 253 * lock itself ). 254 */ 255 if (lkp->lk_lockholder != thr) { 256 lockflags = LK_HAVE_EXCL; 257 if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT)) 258 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; 259 error = acquire(&lkp, extflags, lockflags, &contested, &waitstart); 260 if (error) 261 break; 262 sharelock(td, lkp, 1); 263 if (lkp->lk_sharecount == 1) 264 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 265 266 #if defined(DEBUG_LOCKS) 267 stack_save(&lkp->lk_stack); 268 #endif 269 break; 270 } 271 /* 272 * We hold an exclusive lock, so downgrade it to shared. 273 * An alternative would be to fail with EDEADLK. 274 */ 275 sharelock(td, lkp, 1); 276 if (lkp->lk_sharecount == 1) 277 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 278 /* FALLTHROUGH downgrade */ 279 280 case LK_DOWNGRADE: 281 KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0, 282 ("lockmgr: not holding exclusive lock " 283 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0", 284 lkp->lk_lockholder, thr, lkp->lk_exclusivecount)); 285 sharelock(td, lkp, lkp->lk_exclusivecount); 286 COUNT(td, -lkp->lk_exclusivecount); 287 lkp->lk_exclusivecount = 0; 288 lkp->lk_flags &= ~LK_HAVE_EXCL; 289 lkp->lk_lockholder = LK_NOPROC; 290 if (lkp->lk_waitcount) 291 wakeup((void *)lkp); 292 break; 293 294 case LK_EXCLUPGRADE: 295 /* 296 * If another process is ahead of us to get an upgrade, 297 * then we want to fail rather than have an intervening 298 * exclusive access. 299 */ 300 if (lkp->lk_flags & LK_WANT_UPGRADE) { 301 shareunlock(td, lkp, 1); 302 error = EBUSY; 303 break; 304 } 305 /* FALLTHROUGH normal upgrade */ 306 307 case LK_UPGRADE: 308 /* 309 * Upgrade a shared lock to an exclusive one. If another 310 * shared lock has already requested an upgrade to an 311 * exclusive lock, our shared lock is released and an 312 * exclusive lock is requested (which will be granted 313 * after the upgrade). If we return an error, the file 314 * will always be unlocked. 315 */ 316 if (lkp->lk_lockholder == thr) 317 panic("lockmgr: upgrade exclusive lock"); 318 if (lkp->lk_sharecount <= 0) 319 panic("lockmgr: upgrade without shared"); 320 shareunlock(td, lkp, 1); 321 if (lkp->lk_sharecount == 0) 322 lock_profile_release_lock(&lkp->lk_object); 323 /* 324 * If we are just polling, check to see if we will block. 325 */ 326 if ((extflags & LK_NOWAIT) && 327 ((lkp->lk_flags & LK_WANT_UPGRADE) || 328 lkp->lk_sharecount > 1)) { 329 error = EBUSY; 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 break; 346 } 347 if (lkp->lk_exclusivecount != 0) 348 panic("lockmgr: non-zero exclusive count"); 349 lkp->lk_flags |= LK_HAVE_EXCL; 350 lkp->lk_lockholder = thr; 351 lkp->lk_exclusivecount = 1; 352 COUNT(td, 1); 353 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 354 #if defined(DEBUG_LOCKS) 355 stack_save(&lkp->lk_stack); 356 #endif 357 break; 358 } 359 /* 360 * Someone else has requested upgrade. Release our shared 361 * lock, awaken upgrade requestor if we are the last shared 362 * lock, then request an exclusive lock. 363 */ 364 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 365 LK_WAIT_NONZERO) 366 wakeup((void *)lkp); 367 /* FALLTHROUGH exclusive request */ 368 369 case LK_EXCLUSIVE: 370 if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) { 371 /* 372 * Recursive lock. 373 */ 374 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 375 panic("lockmgr: locking against myself"); 376 if ((extflags & LK_CANRECURSE) != 0) { 377 lkp->lk_exclusivecount++; 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 = thr; 409 if (lkp->lk_exclusivecount != 0) 410 panic("lockmgr: non-zero exclusive count"); 411 lkp->lk_exclusivecount = 1; 412 COUNT(td, 1); 413 lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); 414 #if defined(DEBUG_LOCKS) 415 stack_save(&lkp->lk_stack); 416 #endif 417 break; 418 419 case LK_RELEASE: 420 if (lkp->lk_exclusivecount != 0) { 421 if (lkp->lk_lockholder != thr && 422 lkp->lk_lockholder != LK_KERNPROC) { 423 panic("lockmgr: thread %p, not %s %p unlocking", 424 thr, "exclusive lock holder", 425 lkp->lk_lockholder); 426 } 427 if (lkp->lk_lockholder != LK_KERNPROC) 428 COUNT(td, -1); 429 if (lkp->lk_exclusivecount == 1) { 430 lkp->lk_flags &= ~LK_HAVE_EXCL; 431 lkp->lk_lockholder = LK_NOPROC; 432 lkp->lk_exclusivecount = 0; 433 lock_profile_release_lock(&lkp->lk_object); 434 } else { 435 lkp->lk_exclusivecount--; 436 } 437 } else if (lkp->lk_flags & LK_SHARE_NONZERO) 438 shareunlock(td, lkp, 1); 439 else { 440 printf("lockmgr: thread %p unlocking unheld lock\n", 441 thr); 442 kdb_backtrace(); 443 } 444 445 if (lkp->lk_flags & LK_WAIT_NONZERO) 446 wakeup((void *)lkp); 447 break; 448 449 case LK_DRAIN: 450 /* 451 * Check that we do not already hold the lock, as it can 452 * never drain if we do. Unfortunately, we have no way to 453 * check for holding a shared lock, but at least we can 454 * check for an exclusive one. 455 */ 456 if (lkp->lk_lockholder == thr) 457 panic("lockmgr: draining against myself"); 458 459 error = acquiredrain(lkp, extflags); 460 if (error) 461 break; 462 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 463 lkp->lk_lockholder = thr; 464 lkp->lk_exclusivecount = 1; 465 COUNT(td, 1); 466 #if defined(DEBUG_LOCKS) 467 stack_save(&lkp->lk_stack); 468 #endif 469 break; 470 471 default: 472 mtx_unlock(lkp->lk_interlock); 473 panic("lockmgr: unknown locktype request %d", 474 flags & LK_TYPE_MASK); 475 /* NOTREACHED */ 476 } 477 if ((lkp->lk_flags & LK_WAITDRAIN) && 478 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 479 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 480 lkp->lk_flags &= ~LK_WAITDRAIN; 481 wakeup((void *)&lkp->lk_flags); 482 } 483 mtx_unlock(lkp->lk_interlock); 484 return (error); 485 } 486 487 static int 488 acquiredrain(struct lock *lkp, int extflags) { 489 int error; 490 491 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 492 return EBUSY; 493 } 494 while (lkp->lk_flags & LK_ALL) { 495 lkp->lk_flags |= LK_WAITDRAIN; 496 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio, 497 lkp->lk_wmesg, 498 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 499 if (error) 500 return error; 501 if (extflags & LK_SLEEPFAIL) { 502 return ENOLCK; 503 } 504 } 505 return 0; 506 } 507 508 /* 509 * Initialize a lock; required before use. 510 */ 511 void 512 lockinit(lkp, prio, wmesg, timo, flags) 513 struct lock *lkp; 514 int prio; 515 const char *wmesg; 516 int timo; 517 int flags; 518 { 519 CTR5(KTR_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", " 520 "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags); 521 522 lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder); 523 lkp->lk_flags = (flags & LK_EXTFLG_MASK); 524 lkp->lk_sharecount = 0; 525 lkp->lk_waitcount = 0; 526 lkp->lk_exclusivecount = 0; 527 lkp->lk_prio = prio; 528 lkp->lk_timo = timo; 529 lkp->lk_lockholder = LK_NOPROC; 530 lkp->lk_newlock = NULL; 531 #ifdef DEBUG_LOCKS 532 stack_zero(&lkp->lk_stack); 533 #endif 534 lock_init(&lkp->lk_object, &lock_class_lockmgr, wmesg, NULL, 535 LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE); 536 } 537 538 /* 539 * Destroy a lock. 540 */ 541 void 542 lockdestroy(lkp) 543 struct lock *lkp; 544 { 545 546 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", 547 lkp, lkp->lk_wmesg); 548 lock_destroy(&lkp->lk_object); 549 } 550 551 /* 552 * Determine the status of a lock. 553 */ 554 int 555 lockstatus(lkp, td) 556 struct lock *lkp; 557 struct thread *td; 558 { 559 int lock_type = 0; 560 int interlocked; 561 562 if (!kdb_active) { 563 interlocked = 1; 564 mtx_lock(lkp->lk_interlock); 565 } else 566 interlocked = 0; 567 if (lkp->lk_exclusivecount != 0) { 568 if (td == NULL || lkp->lk_lockholder == td) 569 lock_type = LK_EXCLUSIVE; 570 else 571 lock_type = LK_EXCLOTHER; 572 } else if (lkp->lk_sharecount != 0) 573 lock_type = LK_SHARED; 574 if (interlocked) 575 mtx_unlock(lkp->lk_interlock); 576 return (lock_type); 577 } 578 579 /* 580 * Determine the number of holders of a lock. 581 */ 582 int 583 lockcount(lkp) 584 struct lock *lkp; 585 { 586 int count; 587 588 mtx_lock(lkp->lk_interlock); 589 count = lkp->lk_exclusivecount + lkp->lk_sharecount; 590 mtx_unlock(lkp->lk_interlock); 591 return (count); 592 } 593 594 /* 595 * Determine the number of waiters on a lock. 596 */ 597 int 598 lockwaiters(lkp) 599 struct lock *lkp; 600 { 601 int count; 602 603 mtx_lock(lkp->lk_interlock); 604 count = lkp->lk_waitcount; 605 mtx_unlock(lkp->lk_interlock); 606 return (count); 607 } 608 609 /* 610 * Print out information about state of a lock. Used by VOP_PRINT 611 * routines to display status about contained locks. 612 */ 613 void 614 lockmgr_printinfo(lkp) 615 struct lock *lkp; 616 { 617 618 if (lkp->lk_sharecount) 619 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 620 lkp->lk_sharecount); 621 else if (lkp->lk_flags & LK_HAVE_EXCL) 622 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)", 623 lkp->lk_wmesg, lkp->lk_exclusivecount, 624 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); 625 if (lkp->lk_waitcount > 0) 626 printf(" with %d pending", lkp->lk_waitcount); 627 #ifdef DEBUG_LOCKS 628 stack_print(&lkp->lk_stack); 629 #endif 630 } 631 632 #ifdef DDB 633 /* 634 * Check to see if a thread that is blocked on a sleep queue is actually 635 * blocked on a 'struct lock'. If so, output some details and return true. 636 * If the lock has an exclusive owner, return that in *ownerp. 637 */ 638 int 639 lockmgr_chain(struct thread *td, struct thread **ownerp) 640 { 641 struct lock *lkp; 642 643 lkp = td->td_wchan; 644 645 /* Simple test to see if wchan points to a lockmgr lock. */ 646 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 647 lkp->lk_wmesg == td->td_wmesg) 648 goto ok; 649 650 /* 651 * If this thread is doing a DRAIN, then it would be asleep on 652 * &lkp->lk_flags rather than lkp. 653 */ 654 lkp = (struct lock *)((char *)td->td_wchan - 655 offsetof(struct lock, lk_flags)); 656 if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && 657 lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN)) 658 goto ok; 659 660 /* Doen't seem to be a lockmgr lock. */ 661 return (0); 662 663 ok: 664 /* Ok, we think we have a lockmgr lock, so output some details. */ 665 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); 666 if (lkp->lk_sharecount) { 667 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 668 *ownerp = NULL; 669 } else { 670 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); 671 *ownerp = lkp->lk_lockholder; 672 } 673 return (1); 674 } 675 676 void 677 db_show_lockmgr(struct lock_object *lock) 678 { 679 struct thread *td; 680 struct lock *lkp; 681 682 lkp = (struct lock *)lock; 683 684 db_printf(" lock type: %s\n", lkp->lk_wmesg); 685 db_printf(" state: "); 686 if (lkp->lk_sharecount) 687 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 688 else if (lkp->lk_flags & LK_HAVE_EXCL) { 689 td = lkp->lk_lockholder; 690 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); 691 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, 692 td->td_proc->p_pid, td->td_name); 693 } else 694 db_printf("UNLOCKED\n"); 695 if (lkp->lk_waitcount > 0) 696 db_printf(" waiters: %d\n", lkp->lk_waitcount); 697 } 698 #endif 699