kern_rwlock.c revision 173600
1154941Sjhb/*- 2154941Sjhb * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org> 3154941Sjhb * All rights reserved. 4154941Sjhb * 5154941Sjhb * Redistribution and use in source and binary forms, with or without 6154941Sjhb * modification, are permitted provided that the following conditions 7154941Sjhb * are met: 8154941Sjhb * 1. Redistributions of source code must retain the above copyright 9154941Sjhb * notice, this list of conditions and the following disclaimer. 10154941Sjhb * 2. Redistributions in binary form must reproduce the above copyright 11154941Sjhb * notice, this list of conditions and the following disclaimer in the 12154941Sjhb * documentation and/or other materials provided with the distribution. 13154941Sjhb * 3. Neither the name of the author nor the names of any co-contributors 14154941Sjhb * may be used to endorse or promote products derived from this software 15154941Sjhb * without specific prior written permission. 16154941Sjhb * 17154941Sjhb * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18154941Sjhb * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19154941Sjhb * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20154941Sjhb * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21154941Sjhb * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22154941Sjhb * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23154941Sjhb * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24154941Sjhb * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25154941Sjhb * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26154941Sjhb * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27154941Sjhb * SUCH DAMAGE. 28154941Sjhb */ 29154941Sjhb 30154941Sjhb/* 31154941Sjhb * Machine independent bits of reader/writer lock implementation. 32154941Sjhb */ 33154941Sjhb 34154941Sjhb#include <sys/cdefs.h> 35154941Sjhb__FBSDID("$FreeBSD: head/sys/kern/kern_rwlock.c 173600 2007-11-14 06:21:24Z julian $"); 36154941Sjhb 37154941Sjhb#include "opt_ddb.h" 38167801Sjhb#include "opt_no_adaptive_rwlocks.h" 39154941Sjhb 40154941Sjhb#include <sys/param.h> 41154941Sjhb#include <sys/ktr.h> 42154941Sjhb#include <sys/lock.h> 43154941Sjhb#include <sys/mutex.h> 44154941Sjhb#include <sys/proc.h> 45154941Sjhb#include <sys/rwlock.h> 46154941Sjhb#include <sys/systm.h> 47154941Sjhb#include <sys/turnstile.h> 48171516Sattilio 49154941Sjhb#include <machine/cpu.h> 50154941Sjhb 51171052SattilioCTASSERT((RW_RECURSE & LO_CLASSFLAGS) == RW_RECURSE); 52171052Sattilio 53167801Sjhb#if defined(SMP) && !defined(NO_ADAPTIVE_RWLOCKS) 54167801Sjhb#define ADAPTIVE_RWLOCKS 55167801Sjhb#endif 56167801Sjhb 57154941Sjhb#ifdef DDB 58154941Sjhb#include <ddb/ddb.h> 59154941Sjhb 60154941Sjhbstatic void db_show_rwlock(struct lock_object *lock); 61154941Sjhb#endif 62167368Sjhbstatic void lock_rw(struct lock_object *lock, int how); 63167368Sjhbstatic int unlock_rw(struct lock_object *lock); 64154941Sjhb 65154941Sjhbstruct lock_class lock_class_rw = { 66167365Sjhb .lc_name = "rw", 67167365Sjhb .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_UPGRADABLE, 68154941Sjhb#ifdef DDB 69167365Sjhb .lc_ddb_show = db_show_rwlock, 70154941Sjhb#endif 71167368Sjhb .lc_lock = lock_rw, 72167368Sjhb .lc_unlock = unlock_rw, 73154941Sjhb}; 74154941Sjhb 75157826Sjhb/* 76157826Sjhb * Return a pointer to the owning thread if the lock is write-locked or 77157826Sjhb * NULL if the lock is unlocked or read-locked. 78157826Sjhb */ 79157826Sjhb#define rw_wowner(rw) \ 80154941Sjhb ((rw)->rw_lock & RW_LOCK_READ ? NULL : \ 81154941Sjhb (struct thread *)RW_OWNER((rw)->rw_lock)) 82154941Sjhb 83157826Sjhb/* 84171052Sattilio * Returns if a write owner is recursed. Write ownership is not assured 85171052Sattilio * here and should be previously checked. 86171052Sattilio */ 87171052Sattilio#define rw_recursed(rw) ((rw)->rw_recurse != 0) 88171052Sattilio 89171052Sattilio/* 90171052Sattilio * Return true if curthread helds the lock. 91171052Sattilio */ 92171052Sattilio#define rw_wlocked(rw) (rw_wowner((rw)) == curthread) 93171052Sattilio 94171052Sattilio/* 95157826Sjhb * Return a pointer to the owning thread for this lock who should receive 96157826Sjhb * any priority lent by threads that block on this lock. Currently this 97157826Sjhb * is identical to rw_wowner(). 98157826Sjhb */ 99157826Sjhb#define rw_owner(rw) rw_wowner(rw) 100157826Sjhb 101154941Sjhb#ifndef INVARIANTS 102154941Sjhb#define _rw_assert(rw, what, file, line) 103154941Sjhb#endif 104154941Sjhb 105154941Sjhbvoid 106167368Sjhblock_rw(struct lock_object *lock, int how) 107167368Sjhb{ 108167368Sjhb struct rwlock *rw; 109167368Sjhb 110167368Sjhb rw = (struct rwlock *)lock; 111167368Sjhb if (how) 112167368Sjhb rw_wlock(rw); 113167368Sjhb else 114167368Sjhb rw_rlock(rw); 115167368Sjhb} 116167368Sjhb 117167368Sjhbint 118167368Sjhbunlock_rw(struct lock_object *lock) 119167368Sjhb{ 120167368Sjhb struct rwlock *rw; 121167368Sjhb 122167368Sjhb rw = (struct rwlock *)lock; 123167368Sjhb rw_assert(rw, RA_LOCKED | LA_NOTRECURSED); 124167368Sjhb if (rw->rw_lock & RW_LOCK_READ) { 125167368Sjhb rw_runlock(rw); 126167368Sjhb return (0); 127167368Sjhb } else { 128167368Sjhb rw_wunlock(rw); 129167368Sjhb return (1); 130167368Sjhb } 131167368Sjhb} 132167368Sjhb 133167368Sjhbvoid 134171052Sattiliorw_init_flags(struct rwlock *rw, const char *name, int opts) 135154941Sjhb{ 136171052Sattilio int flags; 137154941Sjhb 138171052Sattilio MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET | 139171052Sattilio RW_RECURSE)) == 0); 140171052Sattilio 141171052Sattilio flags = LO_UPGRADABLE | LO_RECURSABLE; 142171052Sattilio if (opts & RW_DUPOK) 143171052Sattilio flags |= LO_DUPOK; 144171052Sattilio if (opts & RW_NOPROFILE) 145171052Sattilio flags |= LO_NOPROFILE; 146171052Sattilio if (!(opts & RW_NOWITNESS)) 147171052Sattilio flags |= LO_WITNESS; 148171052Sattilio if (opts & RW_QUIET) 149171052Sattilio flags |= LO_QUIET; 150171052Sattilio flags |= opts & RW_RECURSE; 151171052Sattilio 152154941Sjhb rw->rw_lock = RW_UNLOCKED; 153171052Sattilio rw->rw_recurse = 0; 154171052Sattilio lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags); 155154941Sjhb} 156154941Sjhb 157154941Sjhbvoid 158154941Sjhbrw_destroy(struct rwlock *rw) 159154941Sjhb{ 160154941Sjhb 161154941Sjhb KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock not unlocked")); 162171052Sattilio KASSERT(rw->rw_recurse == 0, ("rw lock still recursed")); 163169394Sjhb rw->rw_lock = RW_DESTROYED; 164167787Sjhb lock_destroy(&rw->lock_object); 165154941Sjhb} 166154941Sjhb 167154941Sjhbvoid 168154941Sjhbrw_sysinit(void *arg) 169154941Sjhb{ 170154941Sjhb struct rw_args *args = arg; 171154941Sjhb 172154941Sjhb rw_init(args->ra_rw, args->ra_desc); 173154941Sjhb} 174154941Sjhb 175167024Srwatsonint 176167024Srwatsonrw_wowned(struct rwlock *rw) 177167024Srwatson{ 178167024Srwatson 179167024Srwatson return (rw_wowner(rw) == curthread); 180167024Srwatson} 181167024Srwatson 182154941Sjhbvoid 183154941Sjhb_rw_wlock(struct rwlock *rw, const char *file, int line) 184154941Sjhb{ 185154941Sjhb 186154941Sjhb MPASS(curthread != NULL); 187169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 188169394Sjhb ("rw_wlock() of destroyed rwlock @ %s:%d", file, line)); 189157826Sjhb KASSERT(rw_wowner(rw) != curthread, 190154941Sjhb ("%s (%s): wlock already held @ %s:%d", __func__, 191167787Sjhb rw->lock_object.lo_name, file, line)); 192167787Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 193154941Sjhb line); 194154941Sjhb __rw_wlock(rw, curthread, file, line); 195171052Sattilio LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); 196167787Sjhb WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 197160771Sjhb curthread->td_locks++; 198154941Sjhb} 199154941Sjhb 200154941Sjhbvoid 201154941Sjhb_rw_wunlock(struct rwlock *rw, const char *file, int line) 202154941Sjhb{ 203154941Sjhb 204154941Sjhb MPASS(curthread != NULL); 205169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 206169394Sjhb ("rw_wunlock() of destroyed rwlock @ %s:%d", file, line)); 207154941Sjhb _rw_assert(rw, RA_WLOCKED, file, line); 208160771Sjhb curthread->td_locks--; 209167787Sjhb WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 210171052Sattilio LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file, 211171052Sattilio line); 212171052Sattilio if (!rw_recursed(rw)) 213171052Sattilio lock_profile_release_lock(&rw->lock_object); 214154941Sjhb __rw_wunlock(rw, curthread, file, line); 215154941Sjhb} 216154941Sjhb 217154941Sjhbvoid 218154941Sjhb_rw_rlock(struct rwlock *rw, const char *file, int line) 219154941Sjhb{ 220170295Sjeff struct turnstile *ts; 221167801Sjhb#ifdef ADAPTIVE_RWLOCKS 222157846Sjhb volatile struct thread *owner; 223157851Swkoszek#endif 224171516Sattilio#ifdef LOCK_PROFILING_SHARED 225167307Sjhb uint64_t waittime = 0; 226167054Skmacy int contested = 0; 227171516Sattilio#endif 228154941Sjhb uintptr_t x; 229154941Sjhb 230169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 231169394Sjhb ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); 232157826Sjhb KASSERT(rw_wowner(rw) != curthread, 233154941Sjhb ("%s (%s): wlock already held @ %s:%d", __func__, 234167787Sjhb rw->lock_object.lo_name, file, line)); 235167787Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line); 236154941Sjhb 237154941Sjhb /* 238154941Sjhb * Note that we don't make any attempt to try to block read 239154941Sjhb * locks once a writer has blocked on the lock. The reason is 240154941Sjhb * that we currently allow for read locks to recurse and we 241154941Sjhb * don't keep track of all the holders of read locks. Thus, if 242154941Sjhb * we were to block readers once a writer blocked and a reader 243154941Sjhb * tried to recurse on their reader lock after a writer had 244154941Sjhb * blocked we would end up in a deadlock since the reader would 245154941Sjhb * be blocked on the writer, and the writer would be blocked 246154941Sjhb * waiting for the reader to release its original read lock. 247154941Sjhb */ 248154941Sjhb for (;;) { 249154941Sjhb /* 250154941Sjhb * Handle the easy case. If no other thread has a write 251154941Sjhb * lock, then try to bump up the count of read locks. Note 252154941Sjhb * that we have to preserve the current state of the 253154941Sjhb * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a 254154941Sjhb * read lock, then rw_lock must have changed, so restart 255154941Sjhb * the loop. Note that this handles the case of a 256154941Sjhb * completely unlocked rwlock since such a lock is encoded 257154941Sjhb * as a read lock with no waiters. 258154941Sjhb */ 259154941Sjhb x = rw->rw_lock; 260154941Sjhb if (x & RW_LOCK_READ) { 261154941Sjhb 262154941Sjhb /* 263154941Sjhb * The RW_LOCK_READ_WAITERS flag should only be set 264154941Sjhb * if another thread currently holds a write lock, 265154941Sjhb * and in that case RW_LOCK_READ should be clear. 266154941Sjhb */ 267154941Sjhb MPASS((x & RW_LOCK_READ_WAITERS) == 0); 268154941Sjhb if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, 269154941Sjhb x + RW_ONE_READER)) { 270171516Sattilio#ifdef LOCK_PROFILING_SHARED 271171516Sattilio if (RW_READERS(x) == 0) 272171516Sattilio lock_profile_obtain_lock_success( 273171516Sattilio &rw->lock_object, contested, 274171516Sattilio waittime, file, line); 275171516Sattilio#endif 276167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 277154941Sjhb CTR4(KTR_LOCK, 278154941Sjhb "%s: %p succeed %p -> %p", __func__, 279154941Sjhb rw, (void *)x, 280154941Sjhb (void *)(x + RW_ONE_READER)); 281154941Sjhb break; 282154941Sjhb } 283157846Sjhb cpu_spinwait(); 284154941Sjhb continue; 285154941Sjhb } 286154941Sjhb 287154941Sjhb /* 288154941Sjhb * Okay, now it's the hard case. Some other thread already 289154941Sjhb * has a write lock, so acquire the turnstile lock so we can 290154941Sjhb * begin the process of blocking. 291154941Sjhb */ 292170295Sjeff ts = turnstile_trywait(&rw->lock_object); 293154941Sjhb 294154941Sjhb /* 295154941Sjhb * The lock might have been released while we spun, so 296154941Sjhb * recheck its state and restart the loop if there is no 297154941Sjhb * longer a write lock. 298154941Sjhb */ 299154941Sjhb x = rw->rw_lock; 300154941Sjhb if (x & RW_LOCK_READ) { 301170295Sjeff turnstile_cancel(ts); 302157846Sjhb cpu_spinwait(); 303154941Sjhb continue; 304154941Sjhb } 305154941Sjhb 306154941Sjhb /* 307154941Sjhb * Ok, it's still a write lock. If the RW_LOCK_READ_WAITERS 308154941Sjhb * flag is already set, then we can go ahead and block. If 309154941Sjhb * it is not set then try to set it. If we fail to set it 310154941Sjhb * drop the turnstile lock and restart the loop. 311154941Sjhb */ 312157826Sjhb if (!(x & RW_LOCK_READ_WAITERS)) { 313157826Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, x, 314157826Sjhb x | RW_LOCK_READ_WAITERS)) { 315170295Sjeff turnstile_cancel(ts); 316157826Sjhb cpu_spinwait(); 317157826Sjhb continue; 318157826Sjhb } 319167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 320157826Sjhb CTR2(KTR_LOCK, "%s: %p set read waiters flag", 321157826Sjhb __func__, rw); 322154941Sjhb } 323154941Sjhb 324167801Sjhb#ifdef ADAPTIVE_RWLOCKS 325154941Sjhb /* 326157846Sjhb * If the owner is running on another CPU, spin until 327157846Sjhb * the owner stops running or the state of the lock 328157846Sjhb * changes. 329157846Sjhb */ 330157846Sjhb owner = (struct thread *)RW_OWNER(x); 331157846Sjhb if (TD_IS_RUNNING(owner)) { 332170295Sjeff turnstile_cancel(ts); 333167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 334157846Sjhb CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 335157846Sjhb __func__, rw, owner); 336171516Sattilio#ifdef LOCK_PROFILING_SHARED 337171516Sattilio lock_profile_obtain_lock_failed(&rw->lock_object, 338171516Sattilio &contested, &waittime); 339171516Sattilio#endif 340157846Sjhb while ((struct thread*)RW_OWNER(rw->rw_lock)== owner && 341157846Sjhb TD_IS_RUNNING(owner)) 342157846Sjhb cpu_spinwait(); 343157846Sjhb continue; 344157846Sjhb } 345157846Sjhb#endif 346157846Sjhb 347157846Sjhb /* 348154941Sjhb * We were unable to acquire the lock and the read waiters 349154941Sjhb * flag is set, so we must block on the turnstile. 350154941Sjhb */ 351167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 352154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 353154941Sjhb rw); 354171516Sattilio#ifdef LOCK_PROFILING_SHARED 355171516Sattilio lock_profile_obtain_lock_failed(&rw->lock_object, &contested, 356171516Sattilio &waittime); 357171516Sattilio#endif 358170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); 359167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 360154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 361154941Sjhb __func__, rw); 362154941Sjhb } 363154941Sjhb 364154941Sjhb /* 365154941Sjhb * TODO: acquire "owner of record" here. Here be turnstile dragons 366154941Sjhb * however. turnstiles don't like owners changing between calls to 367154941Sjhb * turnstile_wait() currently. 368154941Sjhb */ 369154941Sjhb 370167787Sjhb LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); 371167787Sjhb WITNESS_LOCK(&rw->lock_object, 0, file, line); 372160771Sjhb curthread->td_locks++; 373154941Sjhb} 374154941Sjhb 375154941Sjhbvoid 376154941Sjhb_rw_runlock(struct rwlock *rw, const char *file, int line) 377154941Sjhb{ 378154941Sjhb struct turnstile *ts; 379154941Sjhb uintptr_t x; 380154941Sjhb 381169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 382169394Sjhb ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); 383154941Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 384160771Sjhb curthread->td_locks--; 385167787Sjhb WITNESS_UNLOCK(&rw->lock_object, 0, file, line); 386167787Sjhb LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); 387154941Sjhb 388154941Sjhb /* TODO: drop "owner of record" here. */ 389154941Sjhb 390154941Sjhb for (;;) { 391154941Sjhb /* 392154941Sjhb * See if there is more than one read lock held. If so, 393154941Sjhb * just drop one and return. 394154941Sjhb */ 395154941Sjhb x = rw->rw_lock; 396154941Sjhb if (RW_READERS(x) > 1) { 397154941Sjhb if (atomic_cmpset_ptr(&rw->rw_lock, x, 398154941Sjhb x - RW_ONE_READER)) { 399167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 400154941Sjhb CTR4(KTR_LOCK, 401154941Sjhb "%s: %p succeeded %p -> %p", 402154941Sjhb __func__, rw, (void *)x, 403154941Sjhb (void *)(x - RW_ONE_READER)); 404154941Sjhb break; 405154941Sjhb } 406154941Sjhb continue; 407167307Sjhb } 408154941Sjhb 409164159Skmacy 410154941Sjhb /* 411154941Sjhb * We should never have read waiters while at least one 412154941Sjhb * thread holds a read lock. (See note above) 413154941Sjhb */ 414154941Sjhb KASSERT(!(x & RW_LOCK_READ_WAITERS), 415154941Sjhb ("%s: waiting readers", __func__)); 416171516Sattilio#ifdef LOCK_PROFILING_SHARED 417171516Sattilio lock_profile_release_lock(&rw->lock_object); 418171516Sattilio#endif 419154941Sjhb 420154941Sjhb /* 421154941Sjhb * If there aren't any waiters for a write lock, then try 422154941Sjhb * to drop it quickly. 423154941Sjhb */ 424154941Sjhb if (!(x & RW_LOCK_WRITE_WAITERS)) { 425154941Sjhb 426154941Sjhb /* 427154941Sjhb * There shouldn't be any flags set and we should 428154941Sjhb * be the only read lock. If we fail to release 429154941Sjhb * the single read lock, then another thread might 430154941Sjhb * have just acquired a read lock, so go back up 431154941Sjhb * to the multiple read locks case. 432154941Sjhb */ 433154941Sjhb MPASS(x == RW_READERS_LOCK(1)); 434154941Sjhb if (atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1), 435154941Sjhb RW_UNLOCKED)) { 436167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 437154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded", 438154941Sjhb __func__, rw); 439154941Sjhb break; 440154941Sjhb } 441154941Sjhb continue; 442154941Sjhb } 443154941Sjhb 444154941Sjhb /* 445154941Sjhb * There should just be one reader with one or more 446154941Sjhb * writers waiting. 447154941Sjhb */ 448154941Sjhb MPASS(x == (RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS)); 449154941Sjhb 450154941Sjhb /* 451154941Sjhb * Ok, we know we have a waiting writer and we think we 452154941Sjhb * are the last reader, so grab the turnstile lock. 453154941Sjhb */ 454170295Sjeff turnstile_chain_lock(&rw->lock_object); 455154941Sjhb 456154941Sjhb /* 457154941Sjhb * Try to drop our lock leaving the lock in a unlocked 458154941Sjhb * state. 459154941Sjhb * 460154941Sjhb * If you wanted to do explicit lock handoff you'd have to 461154941Sjhb * do it here. You'd also want to use turnstile_signal() 462154941Sjhb * and you'd have to handle the race where a higher 463154941Sjhb * priority thread blocks on the write lock before the 464154941Sjhb * thread you wakeup actually runs and have the new thread 465154941Sjhb * "steal" the lock. For now it's a lot simpler to just 466154941Sjhb * wakeup all of the waiters. 467154941Sjhb * 468154941Sjhb * As above, if we fail, then another thread might have 469154941Sjhb * acquired a read lock, so drop the turnstile lock and 470154941Sjhb * restart. 471154941Sjhb */ 472154941Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, 473154941Sjhb RW_READERS_LOCK(1) | RW_LOCK_WRITE_WAITERS, RW_UNLOCKED)) { 474170295Sjeff turnstile_chain_unlock(&rw->lock_object); 475154941Sjhb continue; 476154941Sjhb } 477167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 478154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", 479154941Sjhb __func__, rw); 480154941Sjhb 481154941Sjhb /* 482154941Sjhb * Ok. The lock is released and all that's left is to 483154941Sjhb * wake up the waiters. Note that the lock might not be 484154941Sjhb * free anymore, but in that case the writers will just 485154941Sjhb * block again if they run before the new lock holder(s) 486154941Sjhb * release the lock. 487154941Sjhb */ 488167787Sjhb ts = turnstile_lookup(&rw->lock_object); 489157846Sjhb MPASS(ts != NULL); 490154941Sjhb turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE); 491154941Sjhb turnstile_unpend(ts, TS_SHARED_LOCK); 492170295Sjeff turnstile_chain_unlock(&rw->lock_object); 493154941Sjhb break; 494154941Sjhb } 495154941Sjhb} 496154941Sjhb 497154941Sjhb/* 498154941Sjhb * This function is called when we are unable to obtain a write lock on the 499154941Sjhb * first try. This means that at least one other thread holds either a 500154941Sjhb * read or write lock. 501154941Sjhb */ 502154941Sjhbvoid 503154941Sjhb_rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 504154941Sjhb{ 505170295Sjeff struct turnstile *ts; 506167801Sjhb#ifdef ADAPTIVE_RWLOCKS 507157846Sjhb volatile struct thread *owner; 508157851Swkoszek#endif 509171516Sattilio uint64_t waittime = 0; 510154941Sjhb uintptr_t v; 511171516Sattilio int contested = 0; 512154941Sjhb 513171052Sattilio if (rw_wlocked(rw)) { 514171052Sattilio KASSERT(rw->lock_object.lo_flags & RW_RECURSE, 515171052Sattilio ("%s: recursing but non-recursive rw %s @ %s:%d\n", 516171052Sattilio __func__, rw->lock_object.lo_name, file, line)); 517171052Sattilio rw->rw_recurse++; 518171052Sattilio atomic_set_ptr(&rw->rw_lock, RW_LOCK_RECURSED); 519171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 520171052Sattilio CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); 521171052Sattilio return; 522171052Sattilio } 523171052Sattilio 524167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 525154941Sjhb CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 526167787Sjhb rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); 527154941Sjhb 528154941Sjhb while (!_rw_write_lock(rw, tid)) { 529170295Sjeff ts = turnstile_trywait(&rw->lock_object); 530154941Sjhb v = rw->rw_lock; 531154941Sjhb 532154941Sjhb /* 533154941Sjhb * If the lock was released while spinning on the 534154941Sjhb * turnstile chain lock, try again. 535154941Sjhb */ 536154941Sjhb if (v == RW_UNLOCKED) { 537170295Sjeff turnstile_cancel(ts); 538154941Sjhb cpu_spinwait(); 539154941Sjhb continue; 540154941Sjhb } 541154941Sjhb 542154941Sjhb /* 543154941Sjhb * If the lock was released by a writer with both readers 544154941Sjhb * and writers waiting and a reader hasn't woken up and 545154941Sjhb * acquired the lock yet, rw_lock will be set to the 546154941Sjhb * value RW_UNLOCKED | RW_LOCK_WRITE_WAITERS. If we see 547154941Sjhb * that value, try to acquire it once. Note that we have 548154941Sjhb * to preserve the RW_LOCK_WRITE_WAITERS flag as there are 549168073Sjhb * other writers waiting still. If we fail, restart the 550154941Sjhb * loop. 551154941Sjhb */ 552154941Sjhb if (v == (RW_UNLOCKED | RW_LOCK_WRITE_WAITERS)) { 553154941Sjhb if (atomic_cmpset_acq_ptr(&rw->rw_lock, 554154941Sjhb RW_UNLOCKED | RW_LOCK_WRITE_WAITERS, 555154941Sjhb tid | RW_LOCK_WRITE_WAITERS)) { 556170295Sjeff turnstile_claim(ts); 557154941Sjhb CTR2(KTR_LOCK, "%s: %p claimed by new writer", 558154941Sjhb __func__, rw); 559154941Sjhb break; 560154941Sjhb } 561170295Sjeff turnstile_cancel(ts); 562154941Sjhb cpu_spinwait(); 563154941Sjhb continue; 564154941Sjhb } 565154941Sjhb 566154941Sjhb /* 567154941Sjhb * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to 568154941Sjhb * set it. If we fail to set it, then loop back and try 569154941Sjhb * again. 570154941Sjhb */ 571157826Sjhb if (!(v & RW_LOCK_WRITE_WAITERS)) { 572157826Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, v, 573157826Sjhb v | RW_LOCK_WRITE_WAITERS)) { 574170295Sjeff turnstile_cancel(ts); 575157826Sjhb cpu_spinwait(); 576157826Sjhb continue; 577157826Sjhb } 578167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 579157826Sjhb CTR2(KTR_LOCK, "%s: %p set write waiters flag", 580157826Sjhb __func__, rw); 581154941Sjhb } 582154941Sjhb 583167801Sjhb#ifdef ADAPTIVE_RWLOCKS 584157846Sjhb /* 585157846Sjhb * If the lock is write locked and the owner is 586157846Sjhb * running on another CPU, spin until the owner stops 587157846Sjhb * running or the state of the lock changes. 588157846Sjhb */ 589157846Sjhb owner = (struct thread *)RW_OWNER(v); 590157846Sjhb if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { 591170295Sjeff turnstile_cancel(ts); 592167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 593157846Sjhb CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 594157846Sjhb __func__, rw, owner); 595171516Sattilio lock_profile_obtain_lock_failed(&rw->lock_object, 596171516Sattilio &contested, &waittime); 597157846Sjhb while ((struct thread*)RW_OWNER(rw->rw_lock)== owner && 598157846Sjhb TD_IS_RUNNING(owner)) 599157846Sjhb cpu_spinwait(); 600157846Sjhb continue; 601157846Sjhb } 602157846Sjhb#endif 603154941Sjhb 604154941Sjhb /* 605154941Sjhb * We were unable to acquire the lock and the write waiters 606154941Sjhb * flag is set, so we must block on the turnstile. 607154941Sjhb */ 608167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 609154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 610154941Sjhb rw); 611171516Sattilio lock_profile_obtain_lock_failed(&rw->lock_object, &contested, 612171516Sattilio &waittime); 613170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); 614167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 615154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 616154941Sjhb __func__, rw); 617154941Sjhb } 618171516Sattilio lock_profile_obtain_lock_success(&rw->lock_object, contested, waittime, 619171516Sattilio file, line); 620154941Sjhb} 621154941Sjhb 622154941Sjhb/* 623154941Sjhb * This function is called if the first try at releasing a write lock failed. 624154941Sjhb * This means that one of the 2 waiter bits must be set indicating that at 625154941Sjhb * least one thread is waiting on this lock. 626154941Sjhb */ 627154941Sjhbvoid 628154941Sjhb_rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 629154941Sjhb{ 630154941Sjhb struct turnstile *ts; 631154941Sjhb uintptr_t v; 632154941Sjhb int queue; 633154941Sjhb 634171052Sattilio if (rw_wlocked(rw) && rw_recursed(rw)) { 635171052Sattilio if ((--rw->rw_recurse) == 0) 636171052Sattilio atomic_clear_ptr(&rw->rw_lock, RW_LOCK_RECURSED); 637171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 638171052Sattilio CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); 639171052Sattilio return; 640171052Sattilio } 641171052Sattilio 642154941Sjhb KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), 643154941Sjhb ("%s: neither of the waiter flags are set", __func__)); 644154941Sjhb 645167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 646154941Sjhb CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); 647154941Sjhb 648170295Sjeff turnstile_chain_lock(&rw->lock_object); 649167787Sjhb ts = turnstile_lookup(&rw->lock_object); 650154941Sjhb 651167801Sjhb#ifdef ADAPTIVE_RWLOCKS 652157846Sjhb /* 653157846Sjhb * There might not be a turnstile for this lock if all of 654157846Sjhb * the waiters are adaptively spinning. In that case, just 655157846Sjhb * reset the lock to the unlocked state and return. 656157846Sjhb */ 657157846Sjhb if (ts == NULL) { 658157846Sjhb atomic_store_rel_ptr(&rw->rw_lock, RW_UNLOCKED); 659167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 660157846Sjhb CTR2(KTR_LOCK, "%s: %p no sleepers", __func__, rw); 661170295Sjeff turnstile_chain_unlock(&rw->lock_object); 662157846Sjhb return; 663157846Sjhb } 664157846Sjhb#else 665154941Sjhb MPASS(ts != NULL); 666157846Sjhb#endif 667154941Sjhb 668154941Sjhb /* 669154941Sjhb * Use the same algo as sx locks for now. Prefer waking up shared 670154941Sjhb * waiters if we have any over writers. This is probably not ideal. 671154941Sjhb * 672154941Sjhb * 'v' is the value we are going to write back to rw_lock. If we 673154941Sjhb * have waiters on both queues, we need to preserve the state of 674154941Sjhb * the waiter flag for the queue we don't wake up. For now this is 675154941Sjhb * hardcoded for the algorithm mentioned above. 676154941Sjhb * 677154941Sjhb * In the case of both readers and writers waiting we wakeup the 678154941Sjhb * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a 679154941Sjhb * new writer comes in before a reader it will claim the lock up 680154941Sjhb * above. There is probably a potential priority inversion in 681154941Sjhb * there that could be worked around either by waking both queues 682154941Sjhb * of waiters or doing some complicated lock handoff gymnastics. 683157846Sjhb * 684167801Sjhb * Note that in the ADAPTIVE_RWLOCKS case, if both flags are 685167801Sjhb * set, there might not be any actual writers on the turnstile 686167801Sjhb * as they might all be spinning. In that case, we don't want 687167801Sjhb * to preserve the RW_LOCK_WRITE_WAITERS flag as the turnstile 688167801Sjhb * is going to go away once we wakeup all the readers. 689154941Sjhb */ 690157846Sjhb v = RW_UNLOCKED; 691154941Sjhb if (rw->rw_lock & RW_LOCK_READ_WAITERS) { 692154941Sjhb queue = TS_SHARED_QUEUE; 693167801Sjhb#ifdef ADAPTIVE_RWLOCKS 694157846Sjhb if (rw->rw_lock & RW_LOCK_WRITE_WAITERS && 695157846Sjhb !turnstile_empty(ts, TS_EXCLUSIVE_QUEUE)) 696157846Sjhb v |= RW_LOCK_WRITE_WAITERS; 697157846Sjhb#else 698157846Sjhb v |= (rw->rw_lock & RW_LOCK_WRITE_WAITERS); 699157846Sjhb#endif 700157846Sjhb } else 701154941Sjhb queue = TS_EXCLUSIVE_QUEUE; 702157846Sjhb 703167801Sjhb#ifdef ADAPTIVE_RWLOCKS 704157846Sjhb /* 705157846Sjhb * We have to make sure that we actually have waiters to 706157846Sjhb * wakeup. If they are all spinning, then we just need to 707157846Sjhb * disown the turnstile and return. 708157846Sjhb */ 709157846Sjhb if (turnstile_empty(ts, queue)) { 710167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 711157846Sjhb CTR2(KTR_LOCK, "%s: %p no sleepers 2", __func__, rw); 712157846Sjhb atomic_store_rel_ptr(&rw->rw_lock, v); 713157846Sjhb turnstile_disown(ts); 714170295Sjeff turnstile_chain_unlock(&rw->lock_object); 715157846Sjhb return; 716154941Sjhb } 717157846Sjhb#endif 718157846Sjhb 719157846Sjhb /* Wake up all waiters for the specific queue. */ 720167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 721154941Sjhb CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, 722154941Sjhb queue == TS_SHARED_QUEUE ? "read" : "write"); 723154941Sjhb turnstile_broadcast(ts, queue); 724154941Sjhb atomic_store_rel_ptr(&rw->rw_lock, v); 725154941Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 726170295Sjeff turnstile_chain_unlock(&rw->lock_object); 727154941Sjhb} 728154941Sjhb 729157882Sjhb/* 730157882Sjhb * Attempt to do a non-blocking upgrade from a read lock to a write 731157882Sjhb * lock. This will only succeed if this thread holds a single read 732157882Sjhb * lock. Returns true if the upgrade succeeded and false otherwise. 733157882Sjhb */ 734157882Sjhbint 735157882Sjhb_rw_try_upgrade(struct rwlock *rw, const char *file, int line) 736157882Sjhb{ 737157882Sjhb uintptr_t v, tid; 738170295Sjeff struct turnstile *ts; 739157882Sjhb int success; 740157882Sjhb 741169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 742169394Sjhb ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); 743157882Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 744157882Sjhb 745157882Sjhb /* 746157882Sjhb * Attempt to switch from one reader to a writer. If there 747157882Sjhb * are any write waiters, then we will have to lock the 748157882Sjhb * turnstile first to prevent races with another writer 749157882Sjhb * calling turnstile_wait() before we have claimed this 750157882Sjhb * turnstile. So, do the simple case of no waiters first. 751157882Sjhb */ 752157882Sjhb tid = (uintptr_t)curthread; 753157882Sjhb if (!(rw->rw_lock & RW_LOCK_WRITE_WAITERS)) { 754168073Sjhb success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1), 755168073Sjhb tid); 756157882Sjhb goto out; 757157882Sjhb } 758157882Sjhb 759157882Sjhb /* 760157882Sjhb * Ok, we think we have write waiters, so lock the 761157882Sjhb * turnstile. 762157882Sjhb */ 763170295Sjeff ts = turnstile_trywait(&rw->lock_object); 764157882Sjhb 765157882Sjhb /* 766157882Sjhb * Try to switch from one reader to a writer again. This time 767157882Sjhb * we honor the current state of the RW_LOCK_WRITE_WAITERS 768157882Sjhb * flag. If we obtain the lock with the flag set, then claim 769167801Sjhb * ownership of the turnstile. In the ADAPTIVE_RWLOCKS case 770167801Sjhb * it is possible for there to not be an associated turnstile 771167801Sjhb * even though there are waiters if all of the waiters are 772167801Sjhb * spinning. 773157882Sjhb */ 774157882Sjhb v = rw->rw_lock & RW_LOCK_WRITE_WAITERS; 775168073Sjhb success = atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, 776157882Sjhb tid | v); 777167801Sjhb#ifdef ADAPTIVE_RWLOCKS 778167787Sjhb if (success && v && turnstile_lookup(&rw->lock_object) != NULL) 779157882Sjhb#else 780157882Sjhb if (success && v) 781157882Sjhb#endif 782170295Sjeff turnstile_claim(ts); 783157882Sjhb else 784170295Sjeff turnstile_cancel(ts); 785157882Sjhbout: 786167787Sjhb LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); 787157882Sjhb if (success) 788167787Sjhb WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 789157882Sjhb file, line); 790157882Sjhb return (success); 791157882Sjhb} 792157882Sjhb 793157882Sjhb/* 794157882Sjhb * Downgrade a write lock into a single read lock. 795157882Sjhb */ 796157882Sjhbvoid 797157882Sjhb_rw_downgrade(struct rwlock *rw, const char *file, int line) 798157882Sjhb{ 799157882Sjhb struct turnstile *ts; 800157882Sjhb uintptr_t tid, v; 801157882Sjhb 802169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 803169394Sjhb ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); 804171052Sattilio _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); 805171052Sattilio#ifndef INVARIANTS 806171052Sattilio if (rw_recursed(rw)) 807171052Sattilio panic("downgrade of a recursed lock"); 808171052Sattilio#endif 809157882Sjhb 810167787Sjhb WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); 811157882Sjhb 812157882Sjhb /* 813157882Sjhb * Convert from a writer to a single reader. First we handle 814157882Sjhb * the easy case with no waiters. If there are any waiters, we 815157882Sjhb * lock the turnstile, "disown" the lock, and awaken any read 816157882Sjhb * waiters. 817157882Sjhb */ 818157882Sjhb tid = (uintptr_t)curthread; 819157882Sjhb if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) 820157882Sjhb goto out; 821157882Sjhb 822157882Sjhb /* 823157882Sjhb * Ok, we think we have waiters, so lock the turnstile so we can 824157882Sjhb * read the waiter flags without any races. 825157882Sjhb */ 826170295Sjeff turnstile_chain_lock(&rw->lock_object); 827157882Sjhb v = rw->rw_lock; 828157882Sjhb MPASS(v & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)); 829157882Sjhb 830157882Sjhb /* 831157882Sjhb * Downgrade from a write lock while preserving 832157882Sjhb * RW_LOCK_WRITE_WAITERS and give up ownership of the 833157882Sjhb * turnstile. If there are any read waiters, wake them up. 834157882Sjhb * 835167801Sjhb * For ADAPTIVE_RWLOCKS, we have to allow for the fact that 836167801Sjhb * all of the read waiters might be spinning. In that case, 837167801Sjhb * act as if RW_LOCK_READ_WAITERS is not set. Also, only 838167801Sjhb * preserve the RW_LOCK_WRITE_WAITERS flag if at least one 839167801Sjhb * writer is blocked on the turnstile. 840157882Sjhb */ 841167787Sjhb ts = turnstile_lookup(&rw->lock_object); 842167801Sjhb#ifdef ADAPTIVE_RWLOCKS 843157882Sjhb if (ts == NULL) 844157882Sjhb v &= ~(RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS); 845157882Sjhb else if (v & RW_LOCK_READ_WAITERS && 846157882Sjhb turnstile_empty(ts, TS_SHARED_QUEUE)) 847157882Sjhb v &= ~RW_LOCK_READ_WAITERS; 848157882Sjhb else if (v & RW_LOCK_WRITE_WAITERS && 849157882Sjhb turnstile_empty(ts, TS_EXCLUSIVE_QUEUE)) 850157882Sjhb v &= ~RW_LOCK_WRITE_WAITERS; 851157882Sjhb#else 852157882Sjhb MPASS(ts != NULL); 853157882Sjhb#endif 854157882Sjhb if (v & RW_LOCK_READ_WAITERS) 855157882Sjhb turnstile_broadcast(ts, TS_SHARED_QUEUE); 856157882Sjhb atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | 857157882Sjhb (v & RW_LOCK_WRITE_WAITERS)); 858157882Sjhb if (v & RW_LOCK_READ_WAITERS) 859157882Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 860170295Sjeff else if (ts) 861157882Sjhb turnstile_disown(ts); 862170295Sjeff turnstile_chain_unlock(&rw->lock_object); 863157882Sjhbout: 864167787Sjhb LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); 865157882Sjhb} 866157882Sjhb 867154941Sjhb#ifdef INVARIANT_SUPPORT 868155162Sscottl#ifndef INVARIANTS 869154941Sjhb#undef _rw_assert 870154941Sjhb#endif 871154941Sjhb 872154941Sjhb/* 873154941Sjhb * In the non-WITNESS case, rw_assert() can only detect that at least 874154941Sjhb * *some* thread owns an rlock, but it cannot guarantee that *this* 875154941Sjhb * thread owns an rlock. 876154941Sjhb */ 877154941Sjhbvoid 878154941Sjhb_rw_assert(struct rwlock *rw, int what, const char *file, int line) 879154941Sjhb{ 880154941Sjhb 881154941Sjhb if (panicstr != NULL) 882154941Sjhb return; 883154941Sjhb switch (what) { 884154941Sjhb case RA_LOCKED: 885171052Sattilio case RA_LOCKED | RA_RECURSED: 886171052Sattilio case RA_LOCKED | RA_NOTRECURSED: 887154941Sjhb case RA_RLOCKED: 888154941Sjhb#ifdef WITNESS 889167787Sjhb witness_assert(&rw->lock_object, what, file, line); 890154941Sjhb#else 891154941Sjhb /* 892154941Sjhb * If some other thread has a write lock or we have one 893154941Sjhb * and are asserting a read lock, fail. Also, if no one 894154941Sjhb * has a lock at all, fail. 895154941Sjhb */ 896155061Sscottl if (rw->rw_lock == RW_UNLOCKED || 897155061Sscottl (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || 898157826Sjhb rw_wowner(rw) != curthread))) 899154941Sjhb panic("Lock %s not %slocked @ %s:%d\n", 900167787Sjhb rw->lock_object.lo_name, (what == RA_RLOCKED) ? 901154941Sjhb "read " : "", file, line); 902171052Sattilio 903171052Sattilio if (!(rw->rw_lock & RW_LOCK_READ)) { 904171052Sattilio if (rw_recursed(rw)) { 905171052Sattilio if (what & RA_NOTRECURSED) 906171052Sattilio panic("Lock %s recursed @ %s:%d\n", 907171052Sattilio rw->lock_object.lo_name, file, 908171052Sattilio line); 909171052Sattilio } else if (what & RA_RECURSED) 910171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 911171052Sattilio rw->lock_object.lo_name, file, line); 912171052Sattilio } 913154941Sjhb#endif 914154941Sjhb break; 915154941Sjhb case RA_WLOCKED: 916171052Sattilio case RA_WLOCKED | RA_RECURSED: 917171052Sattilio case RA_WLOCKED | RA_NOTRECURSED: 918157826Sjhb if (rw_wowner(rw) != curthread) 919154941Sjhb panic("Lock %s not exclusively locked @ %s:%d\n", 920167787Sjhb rw->lock_object.lo_name, file, line); 921171052Sattilio if (rw_recursed(rw)) { 922171052Sattilio if (what & RA_NOTRECURSED) 923171052Sattilio panic("Lock %s recursed @ %s:%d\n", 924171052Sattilio rw->lock_object.lo_name, file, line); 925171052Sattilio } else if (what & RA_RECURSED) 926171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 927171052Sattilio rw->lock_object.lo_name, file, line); 928154941Sjhb break; 929154941Sjhb case RA_UNLOCKED: 930154941Sjhb#ifdef WITNESS 931167787Sjhb witness_assert(&rw->lock_object, what, file, line); 932154941Sjhb#else 933154941Sjhb /* 934154941Sjhb * If we hold a write lock fail. We can't reliably check 935154941Sjhb * to see if we hold a read lock or not. 936154941Sjhb */ 937157826Sjhb if (rw_wowner(rw) == curthread) 938154941Sjhb panic("Lock %s exclusively locked @ %s:%d\n", 939167787Sjhb rw->lock_object.lo_name, file, line); 940154941Sjhb#endif 941154941Sjhb break; 942154941Sjhb default: 943154941Sjhb panic("Unknown rw lock assertion: %d @ %s:%d", what, file, 944154941Sjhb line); 945154941Sjhb } 946154941Sjhb} 947154941Sjhb#endif /* INVARIANT_SUPPORT */ 948154941Sjhb 949154941Sjhb#ifdef DDB 950154941Sjhbvoid 951154941Sjhbdb_show_rwlock(struct lock_object *lock) 952154941Sjhb{ 953154941Sjhb struct rwlock *rw; 954154941Sjhb struct thread *td; 955154941Sjhb 956154941Sjhb rw = (struct rwlock *)lock; 957154941Sjhb 958154941Sjhb db_printf(" state: "); 959154941Sjhb if (rw->rw_lock == RW_UNLOCKED) 960154941Sjhb db_printf("UNLOCKED\n"); 961169394Sjhb else if (rw->rw_lock == RW_DESTROYED) { 962169394Sjhb db_printf("DESTROYED\n"); 963169394Sjhb return; 964169394Sjhb } else if (rw->rw_lock & RW_LOCK_READ) 965167504Sjhb db_printf("RLOCK: %ju locks\n", 966167504Sjhb (uintmax_t)(RW_READERS(rw->rw_lock))); 967154941Sjhb else { 968157826Sjhb td = rw_wowner(rw); 969154941Sjhb db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 970173600Sjulian td->td_tid, td->td_proc->p_pid, td->td_name); 971171052Sattilio if (rw_recursed(rw)) 972171052Sattilio db_printf(" recursed: %u\n", rw->rw_recurse); 973154941Sjhb } 974154941Sjhb db_printf(" waiters: "); 975154941Sjhb switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { 976154941Sjhb case RW_LOCK_READ_WAITERS: 977154941Sjhb db_printf("readers\n"); 978154941Sjhb break; 979154941Sjhb case RW_LOCK_WRITE_WAITERS: 980154941Sjhb db_printf("writers\n"); 981154941Sjhb break; 982154941Sjhb case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: 983167492Sjhb db_printf("readers and writers\n"); 984154941Sjhb break; 985154941Sjhb default: 986154941Sjhb db_printf("none\n"); 987154941Sjhb break; 988154941Sjhb } 989154941Sjhb} 990154941Sjhb 991154941Sjhb#endif 992