Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_lock.c
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1 /* 2 * Copyright (c) 1995 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (C) 1997 5 * John S. Dyson. All rights reserved. 6 * Copyright (C) 2013 7 * Matthew Dillon, All rights reserved. 8 * 9 * This code contains ideas from software contributed to Berkeley by 10 * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating 11 * System project at Carnegie-Mellon University. 12 * 13 * Redistribution and use in source and binary forms, with or without 14 * modification, are permitted provided that the following conditions 15 * are met: 16 * 1. Redistributions of source code must retain the above copyright 17 * notice, this list of conditions and the following disclaimer. 18 * 2. Redistributions in binary form must reproduce the above copyright 19 * notice, this list of conditions and the following disclaimer in the 20 * documentation and/or other materials provided with the distribution. 21 * 3. Neither the name of the University nor the names of its contributors 22 * may be used to endorse or promote products derived from this software 23 * without specific prior written permission. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 26 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 27 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 28 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 29 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 30 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 31 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 32 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 33 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 34 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 35 * SUCH DAMAGE. 36 */ 37 38 #include "opt_lint.h" 39 40 #include <sys/param.h> 41 #include <sys/systm.h> 42 #include <sys/kernel.h> 43 #include <sys/proc.h> 44 #include <sys/lock.h> 45 #include <sys/sysctl.h> 46 #include <sys/spinlock.h> 47 #include <sys/thread2.h> 48 #include <sys/spinlock2.h> 49 50 static void undo_upreq(struct lock *lkp); 51 52 /* 53 * Locking primitives implementation. 54 * Locks provide shared/exclusive sychronization. 55 */ 56 57 #ifdef DEBUG_LOCKS 58 #define COUNT(td, x) (td)->td_locks += (x) 59 #else 60 #define COUNT(td, x) 61 #endif 62 63 #define LOCK_WAIT_TIME 100 64 #define LOCK_SAMPLE_WAIT 7 65 66 /* 67 * Set, change, or release a lock. 68 * 69 */ 70 int 71 #ifndef DEBUG_LOCKS 72 lockmgr(struct lock *lkp, u_int flags) 73 #else 74 debuglockmgr(struct lock *lkp, u_int flags, 75 const char *name, const char *file, int line) 76 #endif 77 { 78 thread_t td; 79 thread_t otd; 80 int error; 81 int extflags; 82 int count; 83 int pflags; 84 int wflags; 85 int timo; 86 #ifdef DEBUG_LOCKS 87 int i; 88 #endif 89 90 error = 0; 91 92 if (mycpu->gd_intr_nesting_level && 93 (flags & LK_NOWAIT) == 0 && 94 (flags & LK_TYPE_MASK) != LK_RELEASE && 95 panic_cpu_gd != mycpu 96 ) { 97 98 #ifndef DEBUG_LOCKS 99 panic("lockmgr %s from %p: called from interrupt, ipi, " 100 "or hard code section", 101 lkp->lk_wmesg, ((int **)&lkp)[-1]); 102 #else 103 panic("lockmgr %s from %s:%d: called from interrupt, ipi, " 104 "or hard code section", 105 lkp->lk_wmesg, file, line); 106 #endif 107 } 108 109 #ifdef DEBUG_LOCKS 110 if (mycpu->gd_spinlocks && ((flags & LK_NOWAIT) == 0)) { 111 panic("lockmgr %s from %s:%d: called with %d spinlocks held", 112 lkp->lk_wmesg, file, line, mycpu->gd_spinlocks); 113 } 114 #endif 115 116 extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK; 117 td = curthread; 118 119 again: 120 count = lkp->lk_count; 121 cpu_ccfence(); 122 123 switch (flags & LK_TYPE_MASK) { 124 case LK_SHARED: 125 /* 126 * Shared lock critical path case 127 */ 128 if ((count & (LKC_EXREQ|LKC_UPREQ|LKC_EXCL)) == 0) { 129 if (atomic_cmpset_int(&lkp->lk_count, 130 count, count + 1)) { 131 COUNT(td, 1); 132 break; 133 } 134 goto again; 135 } 136 137 /* 138 * If the caller already holds the lock exclusively then 139 * we silently obtain another count on the exclusive lock. 140 * 141 * WARNING! The old FreeBSD behavior was to downgrade, 142 * but this creates a problem when recursions 143 * return to the caller and the caller expects 144 * its original exclusive lock to remain exclusively 145 * locked. 146 */ 147 if (lkp->lk_lockholder == td) { 148 KKASSERT(count & LKC_EXCL); 149 if ((extflags & LK_CANRECURSE) == 0) { 150 if (extflags & LK_NOWAIT) { 151 error = EBUSY; 152 break; 153 } 154 panic("lockmgr: locking against myself"); 155 } 156 atomic_add_int(&lkp->lk_count, 1); 157 COUNT(td, 1); 158 break; 159 } 160 161 /* 162 * Slow path 163 */ 164 pflags = (extflags & LK_PCATCH) ? PCATCH : 0; 165 timo = (extflags & LK_TIMELOCK) ? lkp->lk_timo : 0; 166 wflags = (td->td_flags & TDF_DEADLKTREAT) ? 167 LKC_EXCL : (LKC_EXCL|LKC_EXREQ|LKC_UPREQ); 168 169 /* 170 * Block while the lock is held exclusively or, conditionally, 171 * if other threads are tring to obtain an exclusive lock or 172 * upgrade to one. 173 */ 174 if (count & wflags) { 175 if (extflags & LK_NOWAIT) { 176 error = EBUSY; 177 break; 178 } 179 tsleep_interlock(lkp, pflags); 180 if (!atomic_cmpset_int(&lkp->lk_count, count, 181 count | LKC_SHREQ)) { 182 goto again; 183 } 184 185 mycpu->gd_cnt.v_lock_name[0] = 'S'; 186 strncpy(mycpu->gd_cnt.v_lock_name + 1, 187 lkp->lk_wmesg, 188 sizeof(mycpu->gd_cnt.v_lock_name) - 2); 189 ++mycpu->gd_cnt.v_lock_colls; 190 191 error = tsleep(lkp, pflags | PINTERLOCKED, 192 lkp->lk_wmesg, timo); 193 if (error) 194 break; 195 if (extflags & LK_SLEEPFAIL) { 196 error = ENOLCK; 197 break; 198 } 199 goto again; 200 } 201 202 /* 203 * Otherwise we can bump the count 204 */ 205 if (atomic_cmpset_int(&lkp->lk_count, count, count + 1)) { 206 COUNT(td, 1); 207 break; 208 } 209 goto again; 210 211 case LK_EXCLUSIVE: 212 /* 213 * Exclusive lock critical path. 214 */ 215 if (count == 0) { 216 if (atomic_cmpset_int(&lkp->lk_count, count, 217 LKC_EXCL | (count + 1))) { 218 lkp->lk_lockholder = td; 219 COUNT(td, 1); 220 break; 221 } 222 goto again; 223 } 224 225 /* 226 * Recursive lock if we already hold it exclusively. 227 */ 228 if (lkp->lk_lockholder == td) { 229 KKASSERT(count & LKC_EXCL); 230 if ((extflags & LK_CANRECURSE) == 0) { 231 if (extflags & LK_NOWAIT) { 232 error = EBUSY; 233 break; 234 } 235 panic("lockmgr: locking against myself"); 236 } 237 atomic_add_int(&lkp->lk_count, 1); 238 COUNT(td, 1); 239 break; 240 } 241 242 /* 243 * We will block, handle LK_NOWAIT 244 */ 245 if (extflags & LK_NOWAIT) { 246 error = EBUSY; 247 break; 248 } 249 250 /* 251 * Wait until we can obtain the exclusive lock. EXREQ is 252 * automatically cleared when all current holders release 253 * so if we abort the operation we can safely leave it set. 254 * There might be other exclusive requesters. 255 */ 256 pflags = (extflags & LK_PCATCH) ? PCATCH : 0; 257 timo = (extflags & LK_TIMELOCK) ? lkp->lk_timo : 0; 258 259 tsleep_interlock(lkp, pflags); 260 if (!atomic_cmpset_int(&lkp->lk_count, count, 261 count | LKC_EXREQ)) { 262 goto again; 263 } 264 265 mycpu->gd_cnt.v_lock_name[0] = 'X'; 266 strncpy(mycpu->gd_cnt.v_lock_name + 1, 267 lkp->lk_wmesg, 268 sizeof(mycpu->gd_cnt.v_lock_name) - 2); 269 ++mycpu->gd_cnt.v_lock_colls; 270 271 error = tsleep(lkp, pflags | PINTERLOCKED, 272 lkp->lk_wmesg, timo); 273 if (error) 274 break; 275 if (extflags & LK_SLEEPFAIL) { 276 error = ENOLCK; 277 break; 278 } 279 goto again; 280 281 case LK_DOWNGRADE: 282 /* 283 * Downgrade an exclusive lock into a shared lock. All 284 * counts on a recursive exclusive lock become shared. 285 * 286 * This function always succeeds. 287 */ 288 if (lkp->lk_lockholder != td || 289 (count & (LKC_EXCL|LKC_MASK)) != (LKC_EXCL|1)) { 290 panic("lockmgr: not holding exclusive lock"); 291 } 292 293 #ifdef DEBUG_LOCKS 294 for (i = 0; i < LOCKMGR_DEBUG_ARRAY_SIZE; i++) { 295 if (td->td_lockmgr_stack[i] == lkp && 296 td->td_lockmgr_stack_id[i] > 0 297 ) { 298 td->td_lockmgr_stack_id[i]--; 299 break; 300 } 301 } 302 #endif 303 /* 304 * NOTE! Must NULL-out lockholder before releasing LKC_EXCL. 305 */ 306 otd = lkp->lk_lockholder; 307 lkp->lk_lockholder = NULL; 308 if (atomic_cmpset_int(&lkp->lk_count, count, 309 count & ~(LKC_EXCL|LKC_SHREQ))) { 310 if (count & LKC_SHREQ) 311 wakeup(lkp); 312 break; 313 } 314 lkp->lk_lockholder = otd; 315 goto again; 316 317 case LK_EXCLUPGRADE: 318 /* 319 * Upgrade from a single shared lock to an exclusive lock. 320 * 321 * If another process is ahead of us to get an upgrade, 322 * then we want to fail rather than have an intervening 323 * exclusive access. The shared lock is released on 324 * failure. 325 */ 326 if (count & LKC_UPREQ) { 327 flags = LK_RELEASE; 328 error = EBUSY; 329 goto again; 330 } 331 /* fall through into normal upgrade */ 332 333 case LK_UPGRADE: 334 /* 335 * Upgrade a shared lock to an exclusive one. This can cause 336 * the lock to be temporarily released and stolen by other 337 * threads. LK_SLEEPFAIL or LK_NOWAIT may be used to detect 338 * this case, or use LK_EXCLUPGRADE. 339 * 340 * If the lock is already exclusively owned by us, this 341 * operation is a NOP. 342 * 343 * If we return an error (even NOWAIT), the current lock will 344 * be released. 345 * 346 * Start with the critical path. 347 */ 348 if ((count & (LKC_UPREQ|LKC_EXCL|LKC_MASK)) == 1) { 349 if (atomic_cmpset_int(&lkp->lk_count, count, 350 count | LKC_EXCL)) { 351 lkp->lk_lockholder = td; 352 break; 353 } 354 goto again; 355 } 356 357 /* 358 * If we already hold the lock exclusively this operation 359 * succeeds and is a NOP. 360 */ 361 if (count & LKC_EXCL) { 362 if (lkp->lk_lockholder == td) 363 break; 364 panic("lockmgr: upgrade unowned lock"); 365 } 366 if ((count & LKC_MASK) == 0) 367 panic("lockmgr: upgrade unowned lock"); 368 369 /* 370 * We cannot upgrade without blocking at this point. 371 */ 372 if (extflags & LK_NOWAIT) { 373 flags = LK_RELEASE; 374 error = EBUSY; 375 goto again; 376 } 377 378 /* 379 * Release the shared lock and request the upgrade. 380 */ 381 pflags = (extflags & LK_PCATCH) ? PCATCH : 0; 382 timo = (extflags & LK_TIMELOCK) ? lkp->lk_timo : 0; 383 tsleep_interlock(lkp, pflags); 384 wflags = (count & LKC_UPREQ) ? LKC_EXREQ : LKC_UPREQ; 385 386 /* 387 * If someone else owns UPREQ and this transition would 388 * allow it to be granted, we have to grant it. Otherwise 389 * we release the shared lock. 390 */ 391 if ((count & (LKC_UPREQ|LKC_MASK)) == (LKC_UPREQ | 1)) { 392 wflags |= LKC_EXCL | LKC_UPGRANT; 393 wflags |= count; 394 wflags &= ~LKC_UPREQ; 395 } else { 396 wflags |= (count - 1); 397 } 398 399 if (atomic_cmpset_int(&lkp->lk_count, count, wflags)) { 400 COUNT(td, -1); 401 402 /* 403 * Must wakeup the thread granted the upgrade. 404 */ 405 if ((count & (LKC_UPREQ|LKC_MASK)) == (LKC_UPREQ | 1)) 406 wakeup(lkp); 407 408 mycpu->gd_cnt.v_lock_name[0] = 'U'; 409 strncpy(mycpu->gd_cnt.v_lock_name + 1, 410 lkp->lk_wmesg, 411 sizeof(mycpu->gd_cnt.v_lock_name) - 2); 412 ++mycpu->gd_cnt.v_lock_colls; 413 414 error = tsleep(lkp, pflags | PINTERLOCKED, 415 lkp->lk_wmesg, timo); 416 if (error) 417 break; 418 if (extflags & LK_SLEEPFAIL) { 419 error = ENOLCK; 420 break; 421 } 422 423 /* 424 * Refactor to either LK_EXCLUSIVE or LK_WAITUPGRADE, 425 * depending on whether we were able to acquire the 426 * LKC_UPREQ bit. 427 */ 428 if (count & LKC_UPREQ) 429 flags = LK_EXCLUSIVE; /* someone else */ 430 else 431 flags = LK_WAITUPGRADE; /* we own the bit */ 432 } 433 goto again; 434 435 case LK_WAITUPGRADE: 436 /* 437 * We own the LKC_UPREQ bit, wait until we are granted the 438 * exclusive lock (LKC_UPGRANT is set). 439 * 440 * IF THE OPERATION FAILS (tsleep error tsleep+LK_SLEEPFAIL), 441 * we have to undo the upgrade request and clean up any lock 442 * that might have been granted via a race. 443 */ 444 if (count & LKC_UPGRANT) { 445 if (atomic_cmpset_int(&lkp->lk_count, count, 446 count & ~LKC_UPGRANT)) { 447 lkp->lk_lockholder = td; 448 KKASSERT(count & LKC_EXCL); 449 break; 450 } 451 /* retry */ 452 } else { 453 pflags = (extflags & LK_PCATCH) ? PCATCH : 0; 454 timo = (extflags & LK_TIMELOCK) ? lkp->lk_timo : 0; 455 tsleep_interlock(lkp, pflags); 456 if (atomic_cmpset_int(&lkp->lk_count, count, count)) { 457 458 mycpu->gd_cnt.v_lock_name[0] = 'U'; 459 strncpy(mycpu->gd_cnt.v_lock_name + 1, 460 lkp->lk_wmesg, 461 sizeof(mycpu->gd_cnt.v_lock_name) - 2); 462 ++mycpu->gd_cnt.v_lock_colls; 463 464 error = tsleep(lkp, pflags | PINTERLOCKED, 465 lkp->lk_wmesg, timo); 466 if (error) { 467 undo_upreq(lkp); 468 break; 469 } 470 if (extflags & LK_SLEEPFAIL) { 471 error = ENOLCK; 472 undo_upreq(lkp); 473 break; 474 } 475 } 476 /* retry */ 477 } 478 goto again; 479 480 case LK_RELEASE: 481 /* 482 * Release the currently held lock. If releasing the current 483 * lock as part of an error return, error will ALREADY be 484 * non-zero. 485 * 486 * When releasing the last lock we automatically transition 487 * LKC_UPREQ to LKC_EXCL|1. 488 * 489 * WARNING! We cannot detect when there are multiple exclusive 490 * requests pending. We clear EXREQ unconditionally 491 * on the 1->0 transition so it is possible for 492 * shared requests to race the next exclusive 493 * request. 494 * 495 * Always succeeds. 496 */ 497 if ((count & LKC_MASK) == 0) 498 panic("lockmgr: LK_RELEASE: no lock held"); 499 500 if (count & LKC_EXCL) { 501 if (lkp->lk_lockholder != LK_KERNTHREAD && 502 lkp->lk_lockholder != td) { 503 panic("lockmgr: pid %d, not exlusive " 504 "lock holder thr %p/%p unlocking", 505 (td->td_proc ? td->td_proc->p_pid : -1), 506 td, lkp->lk_lockholder); 507 } 508 if ((count & (LKC_UPREQ|LKC_MASK)) == 1) { 509 /* 510 * Last exclusive count is being released 511 */ 512 otd = lkp->lk_lockholder; 513 lkp->lk_lockholder = NULL; 514 if (!atomic_cmpset_int(&lkp->lk_count, count, 515 (count - 1) & 516 ~(LKC_EXCL|LKC_EXREQ|LKC_SHREQ))) { 517 lkp->lk_lockholder = otd; 518 goto again; 519 } 520 if (count & (LKC_EXREQ|LKC_SHREQ)) 521 wakeup(lkp); 522 /* success */ 523 } else if ((count & (LKC_UPREQ|LKC_MASK)) == 524 (LKC_UPREQ | 1)) { 525 /* 526 * Last exclusive count is being released but 527 * an upgrade request is present, automatically 528 * grant an exclusive state to the owner of 529 * the upgrade request. 530 */ 531 otd = lkp->lk_lockholder; 532 lkp->lk_lockholder = NULL; 533 if (!atomic_cmpset_int(&lkp->lk_count, count, 534 (count & ~LKC_UPREQ) | 535 LKC_UPGRANT)) { 536 lkp->lk_lockholder = otd; 537 } 538 wakeup(lkp); 539 /* success */ 540 } else { 541 otd = lkp->lk_lockholder; 542 if (!atomic_cmpset_int(&lkp->lk_count, count, 543 count - 1)) { 544 goto again; 545 } 546 /* success */ 547 } 548 /* success */ 549 if (otd != LK_KERNTHREAD) 550 COUNT(td, -1); 551 } else { 552 if ((count & (LKC_UPREQ|LKC_MASK)) == 1) { 553 /* 554 * Last shared count is being released. 555 */ 556 if (!atomic_cmpset_int(&lkp->lk_count, count, 557 (count - 1) & 558 ~(LKC_EXREQ|LKC_SHREQ))) { 559 goto again; 560 } 561 if (count & (LKC_EXREQ|LKC_SHREQ)) 562 wakeup(lkp); 563 /* success */ 564 } else if ((count & (LKC_UPREQ|LKC_MASK)) == 565 (LKC_UPREQ | 1)) { 566 /* 567 * Last shared count is being released but 568 * an upgrade request is present, automatically 569 * grant an exclusive state to the owner of 570 * the upgrade request. 571 */ 572 if (!atomic_cmpset_int(&lkp->lk_count, count, 573 (count & ~LKC_UPREQ) | 574 LKC_EXCL | LKC_UPGRANT)) { 575 goto again; 576 } 577 wakeup(lkp); 578 } else { 579 if (!atomic_cmpset_int(&lkp->lk_count, count, 580 count - 1)) { 581 goto again; 582 } 583 } 584 /* success */ 585 COUNT(td, -1); 586 } 587 break; 588 589 default: 590 panic("lockmgr: unknown locktype request %d", 591 flags & LK_TYPE_MASK); 592 /* NOTREACHED */ 593 } 594 return (error); 595 } 596 597 /* 598 * Undo an upgrade request 599 */ 600 static 601 void 602 undo_upreq(struct lock *lkp) 603 { 604 int count; 605 606 for (;;) { 607 count = lkp->lk_count; 608 cpu_ccfence(); 609 if (count & LKC_UPGRANT) { 610 /* 611 * UPREQ was shifted to UPGRANT. We own UPGRANT now, 612 * another thread might own UPREQ. Clear UPGRANT 613 * and release the granted lock. 614 */ 615 if (atomic_cmpset_int(&lkp->lk_count, count, 616 count & ~LKC_UPGRANT)) { 617 lockmgr(lkp, LK_RELEASE); 618 break; 619 } 620 } else if (count & LKC_EXCL) { 621 /* 622 * Clear the UPREQ we still own. Nobody to wakeup 623 * here because there is an existing exclusive 624 * holder. 625 */ 626 KKASSERT(count & LKC_UPREQ); 627 KKASSERT((count & LKC_MASK) > 0); 628 if (atomic_cmpset_int(&lkp->lk_count, count, 629 count & ~LKC_UPREQ)) { 630 wakeup(lkp); 631 break; 632 } 633 } else if (count & LKC_EXREQ) { 634 /* 635 * Clear the UPREQ we still own. We cannot wakeup any 636 * shared waiters because there is an exclusive 637 * request pending. 638 */ 639 KKASSERT(count & LKC_UPREQ); 640 KKASSERT((count & LKC_MASK) > 0); 641 if (atomic_cmpset_int(&lkp->lk_count, count, 642 count & ~LKC_UPREQ)) { 643 break; 644 } 645 } else { 646 /* 647 * Clear the UPREQ we still own. Wakeup any shared 648 * waiters. 649 */ 650 KKASSERT(count & LKC_UPREQ); 651 KKASSERT((count & LKC_MASK) > 0); 652 if (atomic_cmpset_int(&lkp->lk_count, count, 653 count & 654 ~(LKC_UPREQ | LKC_SHREQ))) { 655 if (count & LKC_SHREQ) 656 wakeup(lkp); 657 break; 658 } 659 } 660 /* retry */ 661 } 662 } 663 664 void 665 lockmgr_kernproc(struct lock *lp) 666 { 667 struct thread *td __debugvar = curthread; 668 669 if (lp->lk_lockholder != LK_KERNTHREAD) { 670 KASSERT(lp->lk_lockholder == td, 671 ("lockmgr_kernproc: lock not owned by curthread %p", td)); 672 lp->lk_lockholder = LK_KERNTHREAD; 673 COUNT(td, -1); 674 } 675 } 676 677 /* 678 * Initialize a lock; required before use. 679 */ 680 void 681 lockinit(struct lock *lkp, const char *wmesg, int timo, int flags) 682 { 683 lkp->lk_flags = (flags & LK_EXTFLG_MASK); 684 lkp->lk_count = 0; 685 lkp->lk_wmesg = wmesg; 686 lkp->lk_timo = timo; 687 lkp->lk_lockholder = LK_NOTHREAD; 688 } 689 690 /* 691 * Reinitialize a lock that is being reused for a different purpose, but 692 * which may have pending (blocked) threads sitting on it. The caller 693 * must already hold the interlock. 694 */ 695 void 696 lockreinit(struct lock *lkp, const char *wmesg, int timo, int flags) 697 { 698 lkp->lk_wmesg = wmesg; 699 lkp->lk_timo = timo; 700 } 701 702 /* 703 * De-initialize a lock. The structure must no longer be used by anyone. 704 */ 705 void 706 lockuninit(struct lock *lkp) 707 { 708 KKASSERT((lkp->lk_count & (LKC_EXREQ|LKC_SHREQ|LKC_UPREQ)) == 0); 709 } 710 711 /* 712 * Determine the status of a lock. 713 */ 714 int 715 lockstatus(struct lock *lkp, struct thread *td) 716 { 717 int lock_type = 0; 718 int count; 719 720 count = lkp->lk_count; 721 cpu_ccfence(); 722 723 if (count & LKC_EXCL) { 724 if (td == NULL || lkp->lk_lockholder == td) 725 lock_type = LK_EXCLUSIVE; 726 else 727 lock_type = LK_EXCLOTHER; 728 } else if (count & LKC_MASK) { 729 lock_type = LK_SHARED; 730 } 731 return (lock_type); 732 } 733 734 /* 735 * Return non-zero if the caller owns the lock shared or exclusive. 736 * We can only guess re: shared locks. 737 */ 738 int 739 lockowned(struct lock *lkp) 740 { 741 thread_t td = curthread; 742 int count; 743 744 count = lkp->lk_count; 745 cpu_ccfence(); 746 747 if (count & LKC_EXCL) 748 return(lkp->lk_lockholder == td); 749 else 750 return((count & LKC_MASK) != 0); 751 } 752 753 /* 754 * Determine the number of holders of a lock. 755 * 756 * The non-blocking version can usually be used for assertions. 757 */ 758 int 759 lockcount(struct lock *lkp) 760 { 761 return(lkp->lk_count & LKC_MASK); 762 } 763 764 int 765 lockcountnb(struct lock *lkp) 766 { 767 return(lkp->lk_count & LKC_MASK); 768 } 769 770 /* 771 * Print out information about state of a lock. Used by VOP_PRINT 772 * routines to display status about contained locks. 773 */ 774 void 775 lockmgr_printinfo(struct lock *lkp) 776 { 777 struct thread *td = lkp->lk_lockholder; 778 struct proc *p; 779 int count; 780 781 count = lkp->lk_count; 782 cpu_ccfence(); 783 784 if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD) 785 p = td->td_proc; 786 else 787 p = NULL; 788 789 if (count & LKC_EXCL) { 790 kprintf(" lock type %s: EXCLUS (count %08x) by td %p pid %d", 791 lkp->lk_wmesg, count, td, 792 p ? p->p_pid : -99); 793 } else if (count & LKC_MASK) { 794 kprintf(" lock type %s: SHARED (count %08x)", 795 lkp->lk_wmesg, count); 796 } else { 797 kprintf(" lock type %s: NOTHELD", lkp->lk_wmesg); 798 } 799 if (count & (LKC_EXREQ|LKC_SHREQ)) 800 kprintf(" with waiters\n"); 801 else 802 kprintf("\n"); 803 } 804 805 void 806 lock_sysinit(struct lock_args *arg) 807 { 808 lockinit(arg->la_lock, arg->la_desc, 0, arg->la_flags); 809 }
Cache object: c37026def061e4324865e9b9b739a1f9
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