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 #ifdef DDB 64 #include <ddb/ddb.h> 65 static void db_show_lockmgr(struct lock_object *lock); 66 #endif 67 68 69 struct lock_class lock_class_lockmgr = { 70 "lockmgr", 71 LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, 72 #ifdef DDB 73 db_show_lockmgr 74 #endif 75 }; 76 77 78 /* 79 * Locking primitives implementation. 80 * Locks provide shared/exclusive sychronization. 81 */ 82 83 #define COUNT(td, x) if ((td)) (td)->td_locks += (x) 84 #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ 85 LK_SHARE_NONZERO | LK_WAIT_NONZERO) 86 87 static int acquire(struct lock **lkpp, int extflags, int wanted); 88 static int acquiredrain(struct lock *lkp, int extflags) ; 89 90 static __inline void 91 sharelock(struct thread *td, struct lock *lkp, int incr) { 92 lkp->lk_flags |= LK_SHARE_NONZERO; 93 lkp->lk_sharecount += incr; 94 COUNT(td, incr); 95 } 96 97 static __inline void 98 shareunlock(struct thread *td, struct lock *lkp, int decr) { 99 100 KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); 101 102 COUNT(td, -decr); 103 if (lkp->lk_sharecount == decr) { 104 lkp->lk_flags &= ~LK_SHARE_NONZERO; 105 if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) { 106 wakeup(lkp); 107 } 108 lkp->lk_sharecount = 0; 109 } else { 110 lkp->lk_sharecount -= decr; 111 } 112 } 113 114 static int 115 acquire(struct lock **lkpp, int extflags, int wanted) 116 { 117 struct lock *lkp = *lkpp; 118 int error; 119 CTR3(KTR_LOCK, 120 "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", 121 lkp, extflags, wanted); 122 123 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) 124 return EBUSY; 125 error = 0; 126 while ((lkp->lk_flags & wanted) != 0) { 127 CTR2(KTR_LOCK, 128 "acquire(): lkp == %p, lk_flags == 0x%x sleeping", 129 lkp, lkp->lk_flags); 130 lkp->lk_flags |= LK_WAIT_NONZERO; 131 lkp->lk_waitcount++; 132 error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio, 133 lkp->lk_wmesg, 134 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 135 lkp->lk_waitcount--; 136 if (lkp->lk_waitcount == 0) 137 lkp->lk_flags &= ~LK_WAIT_NONZERO; 138 if (error) 139 break; 140 if (extflags & LK_SLEEPFAIL) { 141 error = ENOLCK; 142 break; 143 } 144 if (lkp->lk_newlock != NULL) { 145 mtx_lock(lkp->lk_newlock->lk_interlock); 146 mtx_unlock(lkp->lk_interlock); 147 if (lkp->lk_waitcount == 0) 148 wakeup((void *)(&lkp->lk_newlock)); 149 *lkpp = lkp = lkp->lk_newlock; 150 } 151 } 152 mtx_assert(lkp->lk_interlock, MA_OWNED); 153 return (error); 154 } 155 156 /* 157 * Set, change, or release a lock. 158 * 159 * Shared requests increment the shared count. Exclusive requests set the 160 * LK_WANT_EXCL flag (preventing further shared locks), and wait for already 161 * accepted shared locks and shared-to-exclusive upgrades to go away. 162 */ 163 int 164 _lockmgr(struct lock *lkp, int flags, struct mtx *interlkp, 165 struct thread *td, char *file, int line) 166 167 { 168 int error; 169 struct thread *thr; 170 int extflags, lockflags; 171 uint64_t waitstart; 172 173 error = 0; 174 if (td == NULL) 175 thr = LK_KERNPROC; 176 else 177 thr = td; 178 179 lock_profile_waitstart(&waitstart); 180 if ((flags & LK_INTERNAL) == 0) 181 mtx_lock(lkp->lk_interlock); 182 CTR6(KTR_LOCK, 183 "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, " 184 "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder, 185 lkp->lk_exclusivecount, flags, td); 186 #ifdef DEBUG_LOCKS 187 { 188 struct stack stack; /* XXX */ 189 stack_save(&stack); 190 CTRSTACK(KTR_LOCK, &stack, 0, 1); 191 } 192 #endif 193 194 if (flags & LK_INTERLOCK) { 195 mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED); 196 mtx_unlock(interlkp); 197 } 198 199 if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0) 200 WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, 201 &lkp->lk_interlock->mtx_object, 202 "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg); 203 204 if (panicstr != NULL) { 205 mtx_unlock(lkp->lk_interlock); 206 return (0); 207 } 208 if ((lkp->lk_flags & LK_NOSHARE) && 209 (flags & LK_TYPE_MASK) == LK_SHARED) { 210 flags &= ~LK_TYPE_MASK; 211 flags |= LK_EXCLUSIVE; 212 } 213 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 214 215 switch (flags & LK_TYPE_MASK) { 216 217 case LK_SHARED: 218 /* 219 * If we are not the exclusive lock holder, we have to block 220 * while there is an exclusive lock holder or while an 221 * exclusive lock request or upgrade request is in progress. 222 * 223 * However, if TDP_DEADLKTREAT is set, we override exclusive 224 * lock requests or upgrade requests ( but not the exclusive 225 * lock itself ). 226 */ 227 if (lkp->lk_lockholder != thr) { 228 lockflags = LK_HAVE_EXCL; 229 if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT)) 230 lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; 231 error = acquire(&lkp, extflags, lockflags); 232 if (error) 233 break; 234 sharelock(td, lkp, 1); 235 if (lkp->lk_sharecount == 1) 236 lock_profile_obtain_lock_success(&lkp->lk_object, waitstart, file, line); 237 238 #if defined(DEBUG_LOCKS) 239 stack_save(&lkp->lk_stack); 240 #endif 241 break; 242 } 243 /* 244 * We hold an exclusive lock, so downgrade it to shared. 245 * An alternative would be to fail with EDEADLK. 246 */ 247 sharelock(td, lkp, 1); 248 if (lkp->lk_sharecount == 1) 249 lock_profile_obtain_lock_success(&lkp->lk_object, waitstart, file, line); 250 /* FALLTHROUGH downgrade */ 251 252 case LK_DOWNGRADE: 253 KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0, 254 ("lockmgr: not holding exclusive lock " 255 "(owner thread (%p) != thread (%p), exlcnt (%d) != 0", 256 lkp->lk_lockholder, thr, lkp->lk_exclusivecount)); 257 sharelock(td, lkp, lkp->lk_exclusivecount); 258 COUNT(td, -lkp->lk_exclusivecount); 259 lkp->lk_exclusivecount = 0; 260 lkp->lk_flags &= ~LK_HAVE_EXCL; 261 lkp->lk_lockholder = LK_NOPROC; 262 if (lkp->lk_waitcount) 263 wakeup((void *)lkp); 264 break; 265 266 case LK_EXCLUPGRADE: 267 /* 268 * If another process is ahead of us to get an upgrade, 269 * then we want to fail rather than have an intervening 270 * exclusive access. 271 */ 272 if (lkp->lk_flags & LK_WANT_UPGRADE) { 273 shareunlock(td, lkp, 1); 274 error = EBUSY; 275 break; 276 } 277 /* FALLTHROUGH normal upgrade */ 278 279 case LK_UPGRADE: 280 /* 281 * Upgrade a shared lock to an exclusive one. If another 282 * shared lock has already requested an upgrade to an 283 * exclusive lock, our shared lock is released and an 284 * exclusive lock is requested (which will be granted 285 * after the upgrade). If we return an error, the file 286 * will always be unlocked. 287 */ 288 if (lkp->lk_lockholder == thr) 289 panic("lockmgr: upgrade exclusive lock"); 290 if (lkp->lk_sharecount <= 0) 291 panic("lockmgr: upgrade without shared"); 292 shareunlock(td, lkp, 1); 293 if (lkp->lk_sharecount == 0) 294 lock_profile_release_lock(&lkp->lk_object); 295 /* 296 * If we are just polling, check to see if we will block. 297 */ 298 if ((extflags & LK_NOWAIT) && 299 ((lkp->lk_flags & LK_WANT_UPGRADE) || 300 lkp->lk_sharecount > 1)) { 301 error = EBUSY; 302 break; 303 } 304 if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) { 305 /* 306 * We are first shared lock to request an upgrade, so 307 * request upgrade and wait for the shared count to 308 * drop to zero, then take exclusive lock. 309 */ 310 lkp->lk_flags |= LK_WANT_UPGRADE; 311 error = acquire(&lkp, extflags, LK_SHARE_NONZERO); 312 lkp->lk_flags &= ~LK_WANT_UPGRADE; 313 314 if (error) { 315 if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO)) 316 wakeup((void *)lkp); 317 break; 318 } 319 if (lkp->lk_exclusivecount != 0) 320 panic("lockmgr: non-zero exclusive count"); 321 lkp->lk_flags |= LK_HAVE_EXCL; 322 lkp->lk_lockholder = thr; 323 lkp->lk_exclusivecount = 1; 324 COUNT(td, 1); 325 lock_profile_obtain_lock_success(&lkp->lk_object, waitstart, file, line); 326 #if defined(DEBUG_LOCKS) 327 stack_save(&lkp->lk_stack); 328 #endif 329 break; 330 } 331 /* 332 * Someone else has requested upgrade. Release our shared 333 * lock, awaken upgrade requestor if we are the last shared 334 * lock, then request an exclusive lock. 335 */ 336 if ( (lkp->lk_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) == 337 LK_WAIT_NONZERO) 338 wakeup((void *)lkp); 339 /* FALLTHROUGH exclusive request */ 340 341 case LK_EXCLUSIVE: 342 if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) { 343 /* 344 * Recursive lock. 345 */ 346 if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) 347 panic("lockmgr: locking against myself"); 348 if ((extflags & LK_CANRECURSE) != 0) { 349 lkp->lk_exclusivecount++; 350 COUNT(td, 1); 351 break; 352 } 353 } 354 /* 355 * If we are just polling, check to see if we will sleep. 356 */ 357 if ((extflags & LK_NOWAIT) && 358 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) { 359 error = EBUSY; 360 break; 361 } 362 /* 363 * Try to acquire the want_exclusive flag. 364 */ 365 error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL)); 366 if (error) 367 break; 368 lkp->lk_flags |= LK_WANT_EXCL; 369 /* 370 * Wait for shared locks and upgrades to finish. 371 */ 372 error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO); 373 lkp->lk_flags &= ~LK_WANT_EXCL; 374 if (error) { 375 if (lkp->lk_flags & LK_WAIT_NONZERO) 376 wakeup((void *)lkp); 377 break; 378 } 379 lkp->lk_flags |= LK_HAVE_EXCL; 380 lkp->lk_lockholder = thr; 381 if (lkp->lk_exclusivecount != 0) 382 panic("lockmgr: non-zero exclusive count"); 383 lkp->lk_exclusivecount = 1; 384 COUNT(td, 1); 385 lock_profile_obtain_lock_success(&lkp->lk_object, waitstart, file, line); 386 #if defined(DEBUG_LOCKS) 387 stack_save(&lkp->lk_stack); 388 #endif 389 break; 390 391 case LK_RELEASE: 392 if (lkp->lk_exclusivecount != 0) { 393 if (lkp->lk_lockholder != thr && 394 lkp->lk_lockholder != LK_KERNPROC) { 395 panic("lockmgr: thread %p, not %s %p unlocking", 396 thr, "exclusive lock holder", 397 lkp->lk_lockholder); 398 } 399 if (lkp->lk_lockholder != LK_KERNPROC) 400 COUNT(td, -1); 401 if (lkp->lk_exclusivecount == 1) { 402 lkp->lk_flags &= ~LK_HAVE_EXCL; 403 lkp->lk_lockholder = LK_NOPROC; 404 lkp->lk_exclusivecount = 0; 405 lock_profile_release_lock(&lkp->lk_object); 406 } else { 407 lkp->lk_exclusivecount--; 408 } 409 } else if (lkp->lk_flags & LK_SHARE_NONZERO) 410 shareunlock(td, lkp, 1); 411 else { 412 printf("lockmgr: thread %p unlocking unheld lock\n", 413 thr); 414 kdb_backtrace(); 415 } 416 417 if (lkp->lk_flags & LK_WAIT_NONZERO) 418 wakeup((void *)lkp); 419 break; 420 421 case LK_DRAIN: 422 /* 423 * Check that we do not already hold the lock, as it can 424 * never drain if we do. Unfortunately, we have no way to 425 * check for holding a shared lock, but at least we can 426 * check for an exclusive one. 427 */ 428 if (lkp->lk_lockholder == thr) 429 panic("lockmgr: draining against myself"); 430 431 error = acquiredrain(lkp, extflags); 432 if (error) 433 break; 434 lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; 435 lkp->lk_lockholder = thr; 436 lkp->lk_exclusivecount = 1; 437 COUNT(td, 1); 438 #if defined(DEBUG_LOCKS) 439 stack_save(&lkp->lk_stack); 440 #endif 441 break; 442 443 default: 444 mtx_unlock(lkp->lk_interlock); 445 panic("lockmgr: unknown locktype request %d", 446 flags & LK_TYPE_MASK); 447 /* NOTREACHED */ 448 } 449 if ((lkp->lk_flags & LK_WAITDRAIN) && 450 (lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | 451 LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) { 452 lkp->lk_flags &= ~LK_WAITDRAIN; 453 wakeup((void *)&lkp->lk_flags); 454 } 455 mtx_unlock(lkp->lk_interlock); 456 return (error); 457 } 458 459 static int 460 acquiredrain(struct lock *lkp, int extflags) { 461 int error; 462 463 if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) { 464 return EBUSY; 465 } 466 while (lkp->lk_flags & LK_ALL) { 467 lkp->lk_flags |= LK_WAITDRAIN; 468 error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio, 469 lkp->lk_wmesg, 470 ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0)); 471 if (error) 472 return error; 473 if (extflags & LK_SLEEPFAIL) { 474 return ENOLCK; 475 } 476 } 477 return 0; 478 } 479 480 /* 481 * Transfer any waiting processes from one lock to another. 482 */ 483 void 484 transferlockers(from, to) 485 struct lock *from; 486 struct lock *to; 487 { 488 489 KASSERT(from != to, ("lock transfer to self")); 490 KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock")); 491 492 mtx_lock(from->lk_interlock); 493 if (from->lk_waitcount == 0) { 494 mtx_unlock(from->lk_interlock); 495 return; 496 } 497 from->lk_newlock = to; 498 wakeup((void *)from); 499 msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio, 500 "lkxfer", 0); 501 from->lk_newlock = NULL; 502 from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE); 503 KASSERT(from->lk_waitcount == 0, ("active lock")); 504 mtx_unlock(from->lk_interlock); 505 } 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_wmesg = wmesg; 529 lkp->lk_timo = timo; 530 lkp->lk_lockholder = LK_NOPROC; 531 lkp->lk_newlock = NULL; 532 #ifdef DEBUG_LOCKS 533 stack_zero(&lkp->lk_stack); 534 #endif 535 lock_profile_object_init(&lkp->lk_object, &lock_class_lockmgr, wmesg); 536 } 537 538 /* 539 * Destroy a lock. 540 */ 541 void 542 lockdestroy(lkp) 543 struct lock *lkp; 544 { 545 CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", 546 lkp, lkp->lk_wmesg); 547 lock_profile_object_destroy(&lkp->lk_object); 548 } 549 550 /* 551 * Determine the status of a lock. 552 */ 553 int 554 lockstatus(lkp, td) 555 struct lock *lkp; 556 struct thread *td; 557 { 558 int lock_type = 0; 559 int interlocked; 560 561 if (!kdb_active) { 562 interlocked = 1; 563 mtx_lock(lkp->lk_interlock); 564 } else 565 interlocked = 0; 566 if (lkp->lk_exclusivecount != 0) { 567 if (td == NULL || lkp->lk_lockholder == td) 568 lock_type = LK_EXCLUSIVE; 569 else 570 lock_type = LK_EXCLOTHER; 571 } else if (lkp->lk_sharecount != 0) 572 lock_type = LK_SHARED; 573 if (interlocked) 574 mtx_unlock(lkp->lk_interlock); 575 return (lock_type); 576 } 577 578 /* 579 * Determine the number of holders of a lock. 580 */ 581 int 582 lockcount(lkp) 583 struct lock *lkp; 584 { 585 int count; 586 587 mtx_lock(lkp->lk_interlock); 588 count = lkp->lk_exclusivecount + lkp->lk_sharecount; 589 mtx_unlock(lkp->lk_interlock); 590 return (count); 591 } 592 593 /* 594 * Determine the number of waiters on a lock. 595 */ 596 int 597 lockwaiters(lkp) 598 struct lock *lkp; 599 { 600 int count; 601 602 mtx_lock(lkp->lk_interlock); 603 count = lkp->lk_waitcount; 604 mtx_unlock(lkp->lk_interlock); 605 return (count); 606 } 607 608 /* 609 * Print out information about state of a lock. Used by VOP_PRINT 610 * routines to display status about contained locks. 611 */ 612 void 613 lockmgr_printinfo(lkp) 614 struct lock *lkp; 615 { 616 617 if (lkp->lk_sharecount) 618 printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg, 619 lkp->lk_sharecount); 620 else if (lkp->lk_flags & LK_HAVE_EXCL) 621 printf(" lock type %s: EXCL (count %d) by thread %p (pid %d)", 622 lkp->lk_wmesg, lkp->lk_exclusivecount, 623 lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); 624 if (lkp->lk_waitcount > 0) 625 printf(" with %d pending", lkp->lk_waitcount); 626 #ifdef DEBUG_LOCKS 627 stack_print(&lkp->lk_stack); 628 #endif 629 } 630 631 #ifdef DDB 632 /* 633 * Check to see if a thread that is blocked on a sleep queue is actually 634 * blocked on a 'struct lock'. If so, output some details and return true. 635 * If the lock has an exclusive owner, return that in *ownerp. 636 */ 637 int 638 lockmgr_chain(struct thread *td, struct thread **ownerp) 639 { 640 struct lock *lkp; 641 642 lkp = td->td_wchan; 643 644 /* Simple test to see if wchan points to a lockmgr lock. */ 645 if (lkp->lk_wmesg != td->td_wmesg) 646 return (0); 647 648 /* Ok, we think we have a lockmgr lock, so output some details. */ 649 db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); 650 if (lkp->lk_sharecount) { 651 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 652 *ownerp = NULL; 653 } else { 654 db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); 655 *ownerp = lkp->lk_lockholder; 656 } 657 return (1); 658 } 659 660 void 661 db_show_lockmgr(struct lock_object *lock) 662 { 663 struct thread *td; 664 struct lock *lkp; 665 666 lkp = (struct lock *)lock; 667 668 db_printf("lock type: %s\n", lkp->lk_wmesg); 669 db_printf("state: "); 670 if (lkp->lk_sharecount) 671 db_printf("SHARED (count %d)\n", lkp->lk_sharecount); 672 else if (lkp->lk_flags & LK_HAVE_EXCL) { 673 td = lkp->lk_lockholder; 674 db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); 675 db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, 676 td->td_proc->p_pid, td->td_proc->p_comm); 677 } else 678 db_printf("UNLOCKED\n"); 679 if (lkp->lk_waitcount > 0) 680 db_printf("waiters: %d\n", lkp->lk_waitcount); 681 } 682 #endif 683