kern_rwlock.c revision 185778
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 185778 2008-12-08 21:46:55Z kmacy $"); 36154941Sjhb 37154941Sjhb#include "opt_ddb.h" 38167801Sjhb#include "opt_no_adaptive_rwlocks.h" 39154941Sjhb 40154941Sjhb#include <sys/param.h> 41154941Sjhb#include <sys/ktr.h> 42177912Sjeff#include <sys/kernel.h> 43154941Sjhb#include <sys/lock.h> 44154941Sjhb#include <sys/mutex.h> 45154941Sjhb#include <sys/proc.h> 46154941Sjhb#include <sys/rwlock.h> 47177912Sjeff#include <sys/sysctl.h> 48154941Sjhb#include <sys/systm.h> 49154941Sjhb#include <sys/turnstile.h> 50171516Sattilio 51154941Sjhb#include <machine/cpu.h> 52154941Sjhb 53171052SattilioCTASSERT((RW_RECURSE & LO_CLASSFLAGS) == RW_RECURSE); 54171052Sattilio 55167801Sjhb#if defined(SMP) && !defined(NO_ADAPTIVE_RWLOCKS) 56167801Sjhb#define ADAPTIVE_RWLOCKS 57167801Sjhb#endif 58167801Sjhb 59177912Sjeff#ifdef ADAPTIVE_RWLOCKS 60177912Sjeffstatic int rowner_retries = 10; 61177912Sjeffstatic int rowner_loops = 10000; 62177912SjeffSYSCTL_NODE(_debug, OID_AUTO, rwlock, CTLFLAG_RD, NULL, "rwlock debugging"); 63177912SjeffSYSCTL_INT(_debug_rwlock, OID_AUTO, retry, CTLFLAG_RW, &rowner_retries, 0, ""); 64177912SjeffSYSCTL_INT(_debug_rwlock, OID_AUTO, loops, CTLFLAG_RW, &rowner_loops, 0, ""); 65177912Sjeff#endif 66177912Sjeff 67154941Sjhb#ifdef DDB 68154941Sjhb#include <ddb/ddb.h> 69154941Sjhb 70154941Sjhbstatic void db_show_rwlock(struct lock_object *lock); 71154941Sjhb#endif 72173733Sattiliostatic void assert_rw(struct lock_object *lock, int what); 73167368Sjhbstatic void lock_rw(struct lock_object *lock, int how); 74167368Sjhbstatic int unlock_rw(struct lock_object *lock); 75154941Sjhb 76154941Sjhbstruct lock_class lock_class_rw = { 77167365Sjhb .lc_name = "rw", 78167365Sjhb .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE | LC_UPGRADABLE, 79173733Sattilio .lc_assert = assert_rw, 80154941Sjhb#ifdef DDB 81167365Sjhb .lc_ddb_show = db_show_rwlock, 82154941Sjhb#endif 83167368Sjhb .lc_lock = lock_rw, 84167368Sjhb .lc_unlock = unlock_rw, 85154941Sjhb}; 86154941Sjhb 87157826Sjhb/* 88157826Sjhb * Return a pointer to the owning thread if the lock is write-locked or 89157826Sjhb * NULL if the lock is unlocked or read-locked. 90157826Sjhb */ 91157826Sjhb#define rw_wowner(rw) \ 92154941Sjhb ((rw)->rw_lock & RW_LOCK_READ ? NULL : \ 93154941Sjhb (struct thread *)RW_OWNER((rw)->rw_lock)) 94154941Sjhb 95157826Sjhb/* 96171052Sattilio * Returns if a write owner is recursed. Write ownership is not assured 97171052Sattilio * here and should be previously checked. 98171052Sattilio */ 99171052Sattilio#define rw_recursed(rw) ((rw)->rw_recurse != 0) 100171052Sattilio 101171052Sattilio/* 102171052Sattilio * Return true if curthread helds the lock. 103171052Sattilio */ 104171052Sattilio#define rw_wlocked(rw) (rw_wowner((rw)) == curthread) 105171052Sattilio 106171052Sattilio/* 107157826Sjhb * Return a pointer to the owning thread for this lock who should receive 108157826Sjhb * any priority lent by threads that block on this lock. Currently this 109157826Sjhb * is identical to rw_wowner(). 110157826Sjhb */ 111157826Sjhb#define rw_owner(rw) rw_wowner(rw) 112157826Sjhb 113154941Sjhb#ifndef INVARIANTS 114154941Sjhb#define _rw_assert(rw, what, file, line) 115154941Sjhb#endif 116154941Sjhb 117154941Sjhbvoid 118173733Sattilioassert_rw(struct lock_object *lock, int what) 119173733Sattilio{ 120173733Sattilio 121173733Sattilio rw_assert((struct rwlock *)lock, what); 122173733Sattilio} 123173733Sattilio 124173733Sattiliovoid 125167368Sjhblock_rw(struct lock_object *lock, int how) 126167368Sjhb{ 127167368Sjhb struct rwlock *rw; 128167368Sjhb 129167368Sjhb rw = (struct rwlock *)lock; 130167368Sjhb if (how) 131167368Sjhb rw_wlock(rw); 132167368Sjhb else 133167368Sjhb rw_rlock(rw); 134167368Sjhb} 135167368Sjhb 136167368Sjhbint 137167368Sjhbunlock_rw(struct lock_object *lock) 138167368Sjhb{ 139167368Sjhb struct rwlock *rw; 140167368Sjhb 141167368Sjhb rw = (struct rwlock *)lock; 142167368Sjhb rw_assert(rw, RA_LOCKED | LA_NOTRECURSED); 143167368Sjhb if (rw->rw_lock & RW_LOCK_READ) { 144167368Sjhb rw_runlock(rw); 145167368Sjhb return (0); 146167368Sjhb } else { 147167368Sjhb rw_wunlock(rw); 148167368Sjhb return (1); 149167368Sjhb } 150167368Sjhb} 151167368Sjhb 152167368Sjhbvoid 153171052Sattiliorw_init_flags(struct rwlock *rw, const char *name, int opts) 154154941Sjhb{ 155171052Sattilio int flags; 156154941Sjhb 157171052Sattilio MPASS((opts & ~(RW_DUPOK | RW_NOPROFILE | RW_NOWITNESS | RW_QUIET | 158171052Sattilio RW_RECURSE)) == 0); 159171052Sattilio 160171052Sattilio flags = LO_UPGRADABLE | LO_RECURSABLE; 161171052Sattilio if (opts & RW_DUPOK) 162171052Sattilio flags |= LO_DUPOK; 163171052Sattilio if (opts & RW_NOPROFILE) 164171052Sattilio flags |= LO_NOPROFILE; 165171052Sattilio if (!(opts & RW_NOWITNESS)) 166171052Sattilio flags |= LO_WITNESS; 167171052Sattilio if (opts & RW_QUIET) 168171052Sattilio flags |= LO_QUIET; 169171052Sattilio flags |= opts & RW_RECURSE; 170171052Sattilio 171154941Sjhb rw->rw_lock = RW_UNLOCKED; 172171052Sattilio rw->rw_recurse = 0; 173171052Sattilio lock_init(&rw->lock_object, &lock_class_rw, name, NULL, flags); 174154941Sjhb} 175154941Sjhb 176154941Sjhbvoid 177154941Sjhbrw_destroy(struct rwlock *rw) 178154941Sjhb{ 179154941Sjhb 180154941Sjhb KASSERT(rw->rw_lock == RW_UNLOCKED, ("rw lock not unlocked")); 181171052Sattilio KASSERT(rw->rw_recurse == 0, ("rw lock still recursed")); 182169394Sjhb rw->rw_lock = RW_DESTROYED; 183167787Sjhb lock_destroy(&rw->lock_object); 184154941Sjhb} 185154941Sjhb 186154941Sjhbvoid 187154941Sjhbrw_sysinit(void *arg) 188154941Sjhb{ 189154941Sjhb struct rw_args *args = arg; 190154941Sjhb 191154941Sjhb rw_init(args->ra_rw, args->ra_desc); 192154941Sjhb} 193154941Sjhb 194185778Skmacyvoid 195185778Skmacyrw_sysinit_flags(void *arg) 196185778Skmacy{ 197185778Skmacy struct rw_args_flags *args = arg; 198185778Skmacy 199185778Skmacy rw_init_flags(args->ra_rw, args->ra_desc, args->ra_flags); 200185778Skmacy} 201185778Skmacy 202167024Srwatsonint 203167024Srwatsonrw_wowned(struct rwlock *rw) 204167024Srwatson{ 205167024Srwatson 206167024Srwatson return (rw_wowner(rw) == curthread); 207167024Srwatson} 208167024Srwatson 209154941Sjhbvoid 210154941Sjhb_rw_wlock(struct rwlock *rw, const char *file, int line) 211154941Sjhb{ 212154941Sjhb 213154941Sjhb MPASS(curthread != NULL); 214169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 215169394Sjhb ("rw_wlock() of destroyed rwlock @ %s:%d", file, line)); 216167787Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 217182914Sjhb line, NULL); 218154941Sjhb __rw_wlock(rw, curthread, file, line); 219171052Sattilio LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); 220167787Sjhb WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 221160771Sjhb curthread->td_locks++; 222154941Sjhb} 223154941Sjhb 224177843Sattilioint 225177843Sattilio_rw_try_wlock(struct rwlock *rw, const char *file, int line) 226177843Sattilio{ 227177843Sattilio int rval; 228177843Sattilio 229177843Sattilio KASSERT(rw->rw_lock != RW_DESTROYED, 230177843Sattilio ("rw_try_wlock() of destroyed rwlock @ %s:%d", file, line)); 231177843Sattilio 232177843Sattilio if (rw_wlocked(rw) && (rw->lock_object.lo_flags & RW_RECURSE) != 0) { 233177843Sattilio rw->rw_recurse++; 234177843Sattilio rval = 1; 235177843Sattilio } else 236177843Sattilio rval = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_UNLOCKED, 237177843Sattilio (uintptr_t)curthread); 238177843Sattilio 239177843Sattilio LOCK_LOG_TRY("WLOCK", &rw->lock_object, 0, rval, file, line); 240177843Sattilio if (rval) { 241177843Sattilio WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 242177843Sattilio file, line); 243177843Sattilio curthread->td_locks++; 244177843Sattilio } 245177843Sattilio return (rval); 246177843Sattilio} 247177843Sattilio 248154941Sjhbvoid 249154941Sjhb_rw_wunlock(struct rwlock *rw, const char *file, int line) 250154941Sjhb{ 251154941Sjhb 252154941Sjhb MPASS(curthread != NULL); 253169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 254169394Sjhb ("rw_wunlock() of destroyed rwlock @ %s:%d", file, line)); 255154941Sjhb _rw_assert(rw, RA_WLOCKED, file, line); 256160771Sjhb curthread->td_locks--; 257167787Sjhb WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 258171052Sattilio LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file, 259171052Sattilio line); 260171052Sattilio if (!rw_recursed(rw)) 261171052Sattilio lock_profile_release_lock(&rw->lock_object); 262154941Sjhb __rw_wunlock(rw, curthread, file, line); 263154941Sjhb} 264176017Sjeff/* 265176017Sjeff * Determines whether a new reader can acquire a lock. Succeeds if the 266176017Sjeff * reader already owns a read lock and the lock is locked for read to 267176017Sjeff * prevent deadlock from reader recursion. Also succeeds if the lock 268176017Sjeff * is unlocked and has no writer waiters or spinners. Failing otherwise 269176017Sjeff * prioritizes writers before readers. 270176017Sjeff */ 271176017Sjeff#define RW_CAN_READ(_rw) \ 272176017Sjeff ((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \ 273176017Sjeff (RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \ 274176017Sjeff RW_LOCK_READ) 275154941Sjhb 276154941Sjhbvoid 277154941Sjhb_rw_rlock(struct rwlock *rw, const char *file, int line) 278154941Sjhb{ 279170295Sjeff struct turnstile *ts; 280167801Sjhb#ifdef ADAPTIVE_RWLOCKS 281157846Sjhb volatile struct thread *owner; 282177912Sjeff int spintries = 0; 283177912Sjeff int i; 284157851Swkoszek#endif 285167307Sjhb uint64_t waittime = 0; 286167054Skmacy int contested = 0; 287176017Sjeff uintptr_t v; 288154941Sjhb 289169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 290169394Sjhb ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); 291157826Sjhb KASSERT(rw_wowner(rw) != curthread, 292154941Sjhb ("%s (%s): wlock already held @ %s:%d", __func__, 293167787Sjhb rw->lock_object.lo_name, file, line)); 294182914Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); 295154941Sjhb 296154941Sjhb for (;;) { 297154941Sjhb /* 298154941Sjhb * Handle the easy case. If no other thread has a write 299154941Sjhb * lock, then try to bump up the count of read locks. Note 300154941Sjhb * that we have to preserve the current state of the 301154941Sjhb * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a 302154941Sjhb * read lock, then rw_lock must have changed, so restart 303154941Sjhb * the loop. Note that this handles the case of a 304154941Sjhb * completely unlocked rwlock since such a lock is encoded 305154941Sjhb * as a read lock with no waiters. 306154941Sjhb */ 307176017Sjeff v = rw->rw_lock; 308176017Sjeff if (RW_CAN_READ(v)) { 309154941Sjhb /* 310154941Sjhb * The RW_LOCK_READ_WAITERS flag should only be set 311176017Sjeff * if the lock has been unlocked and write waiters 312176017Sjeff * were present. 313154941Sjhb */ 314176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, 315176017Sjeff v + RW_ONE_READER)) { 316167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 317154941Sjhb CTR4(KTR_LOCK, 318154941Sjhb "%s: %p succeed %p -> %p", __func__, 319176017Sjeff rw, (void *)v, 320176017Sjeff (void *)(v + RW_ONE_READER)); 321154941Sjhb break; 322154941Sjhb } 323157846Sjhb cpu_spinwait(); 324154941Sjhb continue; 325154941Sjhb } 326174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 327174629Sjeff &contested, &waittime); 328154941Sjhb 329173960Sattilio#ifdef ADAPTIVE_RWLOCKS 330154941Sjhb /* 331173960Sattilio * If the owner is running on another CPU, spin until 332173960Sattilio * the owner stops running or the state of the lock 333173960Sattilio * changes. 334173960Sattilio */ 335176017Sjeff if ((v & RW_LOCK_READ) == 0) { 336176017Sjeff owner = (struct thread *)RW_OWNER(v); 337176017Sjeff if (TD_IS_RUNNING(owner)) { 338176017Sjeff if (LOCK_LOG_TEST(&rw->lock_object, 0)) 339176017Sjeff CTR3(KTR_LOCK, 340176017Sjeff "%s: spinning on %p held by %p", 341176017Sjeff __func__, rw, owner); 342176017Sjeff while ((struct thread*)RW_OWNER(rw->rw_lock) == 343176017Sjeff owner && TD_IS_RUNNING(owner)) 344176017Sjeff cpu_spinwait(); 345176017Sjeff continue; 346176017Sjeff } 347177912Sjeff } else if (spintries < rowner_retries) { 348177912Sjeff spintries++; 349177912Sjeff for (i = 0; i < rowner_loops; i++) { 350177912Sjeff v = rw->rw_lock; 351177912Sjeff if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) 352177912Sjeff break; 353177912Sjeff cpu_spinwait(); 354177912Sjeff } 355177912Sjeff if (i != rowner_loops) 356177912Sjeff continue; 357173960Sattilio } 358173960Sattilio#endif 359173960Sattilio 360173960Sattilio /* 361154941Sjhb * Okay, now it's the hard case. Some other thread already 362176017Sjeff * has a write lock or there are write waiters present, 363176017Sjeff * acquire the turnstile lock so we can begin the process 364176017Sjeff * of blocking. 365154941Sjhb */ 366170295Sjeff ts = turnstile_trywait(&rw->lock_object); 367154941Sjhb 368154941Sjhb /* 369154941Sjhb * The lock might have been released while we spun, so 370176017Sjeff * recheck its state and restart the loop if needed. 371154941Sjhb */ 372176017Sjeff v = rw->rw_lock; 373176017Sjeff if (RW_CAN_READ(v)) { 374170295Sjeff turnstile_cancel(ts); 375157846Sjhb cpu_spinwait(); 376154941Sjhb continue; 377154941Sjhb } 378154941Sjhb 379173960Sattilio#ifdef ADAPTIVE_RWLOCKS 380154941Sjhb /* 381173960Sattilio * If the current owner of the lock is executing on another 382173960Sattilio * CPU quit the hard path and try to spin. 383173960Sattilio */ 384176017Sjeff if ((v & RW_LOCK_READ) == 0) { 385176017Sjeff owner = (struct thread *)RW_OWNER(v); 386176017Sjeff if (TD_IS_RUNNING(owner)) { 387176017Sjeff turnstile_cancel(ts); 388176017Sjeff cpu_spinwait(); 389176017Sjeff continue; 390176017Sjeff } 391173960Sattilio } 392173960Sattilio#endif 393173960Sattilio 394173960Sattilio /* 395176017Sjeff * The lock is held in write mode or it already has waiters. 396154941Sjhb */ 397176017Sjeff MPASS(!RW_CAN_READ(v)); 398176017Sjeff 399176017Sjeff /* 400176017Sjeff * If the RW_LOCK_READ_WAITERS flag is already set, then 401176017Sjeff * we can go ahead and block. If it is not set then try 402176017Sjeff * to set it. If we fail to set it drop the turnstile 403176017Sjeff * lock and restart the loop. 404176017Sjeff */ 405176017Sjeff if (!(v & RW_LOCK_READ_WAITERS)) { 406176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 407176017Sjeff v | RW_LOCK_READ_WAITERS)) { 408170295Sjeff turnstile_cancel(ts); 409157826Sjhb cpu_spinwait(); 410157826Sjhb continue; 411157826Sjhb } 412167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 413157826Sjhb CTR2(KTR_LOCK, "%s: %p set read waiters flag", 414157826Sjhb __func__, rw); 415154941Sjhb } 416154941Sjhb 417154941Sjhb /* 418154941Sjhb * We were unable to acquire the lock and the read waiters 419154941Sjhb * flag is set, so we must block on the turnstile. 420154941Sjhb */ 421167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 422154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 423154941Sjhb rw); 424170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); 425167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 426154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 427154941Sjhb __func__, rw); 428154941Sjhb } 429154941Sjhb 430154941Sjhb /* 431154941Sjhb * TODO: acquire "owner of record" here. Here be turnstile dragons 432154941Sjhb * however. turnstiles don't like owners changing between calls to 433154941Sjhb * turnstile_wait() currently. 434154941Sjhb */ 435174629Sjeff lock_profile_obtain_lock_success( &rw->lock_object, contested, 436174629Sjeff waittime, file, line); 437167787Sjhb LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); 438167787Sjhb WITNESS_LOCK(&rw->lock_object, 0, file, line); 439160771Sjhb curthread->td_locks++; 440176017Sjeff curthread->td_rw_rlocks++; 441154941Sjhb} 442154941Sjhb 443177843Sattilioint 444177843Sattilio_rw_try_rlock(struct rwlock *rw, const char *file, int line) 445177843Sattilio{ 446177843Sattilio uintptr_t x; 447177843Sattilio 448177843Sattilio for (;;) { 449177843Sattilio x = rw->rw_lock; 450177843Sattilio KASSERT(rw->rw_lock != RW_DESTROYED, 451177843Sattilio ("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line)); 452177843Sattilio if (!(x & RW_LOCK_READ)) 453177843Sattilio break; 454177843Sattilio if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) { 455177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file, 456177843Sattilio line); 457177843Sattilio WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line); 458177843Sattilio curthread->td_locks++; 459177843Sattilio curthread->td_rw_rlocks++; 460177843Sattilio return (1); 461177843Sattilio } 462177843Sattilio } 463177843Sattilio 464177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line); 465177843Sattilio return (0); 466177843Sattilio} 467177843Sattilio 468154941Sjhbvoid 469154941Sjhb_rw_runlock(struct rwlock *rw, const char *file, int line) 470154941Sjhb{ 471154941Sjhb struct turnstile *ts; 472176017Sjeff uintptr_t x, v, queue; 473154941Sjhb 474169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 475169394Sjhb ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); 476154941Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 477160771Sjhb curthread->td_locks--; 478176017Sjeff curthread->td_rw_rlocks--; 479167787Sjhb WITNESS_UNLOCK(&rw->lock_object, 0, file, line); 480167787Sjhb LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); 481154941Sjhb 482154941Sjhb /* TODO: drop "owner of record" here. */ 483154941Sjhb 484154941Sjhb for (;;) { 485154941Sjhb /* 486154941Sjhb * See if there is more than one read lock held. If so, 487154941Sjhb * just drop one and return. 488154941Sjhb */ 489154941Sjhb x = rw->rw_lock; 490154941Sjhb if (RW_READERS(x) > 1) { 491154941Sjhb if (atomic_cmpset_ptr(&rw->rw_lock, x, 492154941Sjhb x - RW_ONE_READER)) { 493167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 494154941Sjhb CTR4(KTR_LOCK, 495154941Sjhb "%s: %p succeeded %p -> %p", 496154941Sjhb __func__, rw, (void *)x, 497154941Sjhb (void *)(x - RW_ONE_READER)); 498154941Sjhb break; 499154941Sjhb } 500154941Sjhb continue; 501167307Sjhb } 502154941Sjhb /* 503154941Sjhb * If there aren't any waiters for a write lock, then try 504154941Sjhb * to drop it quickly. 505154941Sjhb */ 506176017Sjeff if (!(x & RW_LOCK_WAITERS)) { 507176017Sjeff MPASS((x & ~RW_LOCK_WRITE_SPINNER) == 508176017Sjeff RW_READERS_LOCK(1)); 509176017Sjeff if (atomic_cmpset_ptr(&rw->rw_lock, x, RW_UNLOCKED)) { 510167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 511154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded", 512154941Sjhb __func__, rw); 513154941Sjhb break; 514154941Sjhb } 515154941Sjhb continue; 516154941Sjhb } 517154941Sjhb /* 518176017Sjeff * Ok, we know we have waiters and we think we are the 519176017Sjeff * last reader, so grab the turnstile lock. 520154941Sjhb */ 521170295Sjeff turnstile_chain_lock(&rw->lock_object); 522176017Sjeff v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 523176017Sjeff MPASS(v & RW_LOCK_WAITERS); 524154941Sjhb 525154941Sjhb /* 526154941Sjhb * Try to drop our lock leaving the lock in a unlocked 527154941Sjhb * state. 528154941Sjhb * 529154941Sjhb * If you wanted to do explicit lock handoff you'd have to 530154941Sjhb * do it here. You'd also want to use turnstile_signal() 531154941Sjhb * and you'd have to handle the race where a higher 532154941Sjhb * priority thread blocks on the write lock before the 533154941Sjhb * thread you wakeup actually runs and have the new thread 534154941Sjhb * "steal" the lock. For now it's a lot simpler to just 535154941Sjhb * wakeup all of the waiters. 536154941Sjhb * 537154941Sjhb * As above, if we fail, then another thread might have 538154941Sjhb * acquired a read lock, so drop the turnstile lock and 539154941Sjhb * restart. 540154941Sjhb */ 541176017Sjeff x = RW_UNLOCKED; 542176017Sjeff if (v & RW_LOCK_WRITE_WAITERS) { 543176017Sjeff queue = TS_EXCLUSIVE_QUEUE; 544176017Sjeff x |= (v & RW_LOCK_READ_WAITERS); 545176017Sjeff } else 546176017Sjeff queue = TS_SHARED_QUEUE; 547176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, 548176017Sjeff x)) { 549170295Sjeff turnstile_chain_unlock(&rw->lock_object); 550154941Sjhb continue; 551154941Sjhb } 552167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 553154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", 554154941Sjhb __func__, rw); 555154941Sjhb 556154941Sjhb /* 557154941Sjhb * Ok. The lock is released and all that's left is to 558154941Sjhb * wake up the waiters. Note that the lock might not be 559154941Sjhb * free anymore, but in that case the writers will just 560154941Sjhb * block again if they run before the new lock holder(s) 561154941Sjhb * release the lock. 562154941Sjhb */ 563167787Sjhb ts = turnstile_lookup(&rw->lock_object); 564157846Sjhb MPASS(ts != NULL); 565176017Sjeff turnstile_broadcast(ts, queue); 566154941Sjhb turnstile_unpend(ts, TS_SHARED_LOCK); 567170295Sjeff turnstile_chain_unlock(&rw->lock_object); 568154941Sjhb break; 569154941Sjhb } 570174629Sjeff lock_profile_release_lock(&rw->lock_object); 571154941Sjhb} 572154941Sjhb 573154941Sjhb/* 574154941Sjhb * This function is called when we are unable to obtain a write lock on the 575154941Sjhb * first try. This means that at least one other thread holds either a 576154941Sjhb * read or write lock. 577154941Sjhb */ 578154941Sjhbvoid 579154941Sjhb_rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 580154941Sjhb{ 581170295Sjeff struct turnstile *ts; 582167801Sjhb#ifdef ADAPTIVE_RWLOCKS 583157846Sjhb volatile struct thread *owner; 584176017Sjeff int spintries = 0; 585176017Sjeff int i; 586157851Swkoszek#endif 587171516Sattilio uint64_t waittime = 0; 588176017Sjeff uintptr_t v, x; 589171516Sattilio int contested = 0; 590154941Sjhb 591171052Sattilio if (rw_wlocked(rw)) { 592171052Sattilio KASSERT(rw->lock_object.lo_flags & RW_RECURSE, 593171052Sattilio ("%s: recursing but non-recursive rw %s @ %s:%d\n", 594171052Sattilio __func__, rw->lock_object.lo_name, file, line)); 595171052Sattilio rw->rw_recurse++; 596171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 597171052Sattilio CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); 598171052Sattilio return; 599171052Sattilio } 600171052Sattilio 601167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 602154941Sjhb CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 603167787Sjhb rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); 604154941Sjhb 605154941Sjhb while (!_rw_write_lock(rw, tid)) { 606174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 607174629Sjeff &contested, &waittime); 608173960Sattilio#ifdef ADAPTIVE_RWLOCKS 609173960Sattilio /* 610173960Sattilio * If the lock is write locked and the owner is 611173960Sattilio * running on another CPU, spin until the owner stops 612173960Sattilio * running or the state of the lock changes. 613173960Sattilio */ 614173960Sattilio v = rw->rw_lock; 615173960Sattilio owner = (struct thread *)RW_OWNER(v); 616173960Sattilio if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { 617173960Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 618173960Sattilio CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 619173960Sattilio __func__, rw, owner); 620173960Sattilio while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && 621173960Sattilio TD_IS_RUNNING(owner)) 622173960Sattilio cpu_spinwait(); 623173960Sattilio continue; 624173960Sattilio } 625177912Sjeff if ((v & RW_LOCK_READ) && RW_READERS(v) && 626177912Sjeff spintries < rowner_retries) { 627176017Sjeff if (!(v & RW_LOCK_WRITE_SPINNER)) { 628176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 629176017Sjeff v | RW_LOCK_WRITE_SPINNER)) { 630176017Sjeff cpu_spinwait(); 631176017Sjeff continue; 632176017Sjeff } 633176017Sjeff } 634176017Sjeff spintries++; 635177912Sjeff for (i = 0; i < rowner_loops; i++) { 636176017Sjeff if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) 637176017Sjeff break; 638176017Sjeff cpu_spinwait(); 639176017Sjeff } 640177912Sjeff if (i != rowner_loops) 641176017Sjeff continue; 642176017Sjeff } 643173960Sattilio#endif 644170295Sjeff ts = turnstile_trywait(&rw->lock_object); 645154941Sjhb v = rw->rw_lock; 646154941Sjhb 647173960Sattilio#ifdef ADAPTIVE_RWLOCKS 648154941Sjhb /* 649173960Sattilio * If the current owner of the lock is executing on another 650173960Sattilio * CPU quit the hard path and try to spin. 651173960Sattilio */ 652173960Sattilio if (!(v & RW_LOCK_READ)) { 653173960Sattilio owner = (struct thread *)RW_OWNER(v); 654173960Sattilio if (TD_IS_RUNNING(owner)) { 655173960Sattilio turnstile_cancel(ts); 656173960Sattilio cpu_spinwait(); 657173960Sattilio continue; 658173960Sattilio } 659173960Sattilio } 660173960Sattilio#endif 661173960Sattilio /* 662179334Sattilio * Check for the waiters flags about this rwlock. 663179334Sattilio * If the lock was released, without maintain any pending 664179334Sattilio * waiters queue, simply try to acquire it. 665179334Sattilio * If a pending waiters queue is present, claim the lock 666179334Sattilio * ownership and maintain the pending queue. 667154941Sjhb */ 668176017Sjeff x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 669176017Sjeff if ((v & ~x) == RW_UNLOCKED) { 670176017Sjeff x &= ~RW_LOCK_WRITE_SPINNER; 671176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) { 672176017Sjeff if (x) 673176017Sjeff turnstile_claim(ts); 674176017Sjeff else 675176017Sjeff turnstile_cancel(ts); 676154941Sjhb break; 677154941Sjhb } 678170295Sjeff turnstile_cancel(ts); 679154941Sjhb cpu_spinwait(); 680154941Sjhb continue; 681154941Sjhb } 682154941Sjhb /* 683154941Sjhb * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to 684154941Sjhb * set it. If we fail to set it, then loop back and try 685154941Sjhb * again. 686154941Sjhb */ 687157826Sjhb if (!(v & RW_LOCK_WRITE_WAITERS)) { 688157826Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, v, 689157826Sjhb v | RW_LOCK_WRITE_WAITERS)) { 690170295Sjeff turnstile_cancel(ts); 691157826Sjhb cpu_spinwait(); 692157826Sjhb continue; 693157826Sjhb } 694167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 695157826Sjhb CTR2(KTR_LOCK, "%s: %p set write waiters flag", 696157826Sjhb __func__, rw); 697154941Sjhb } 698157846Sjhb /* 699154941Sjhb * We were unable to acquire the lock and the write waiters 700154941Sjhb * flag is set, so we must block on the turnstile. 701154941Sjhb */ 702167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 703154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 704154941Sjhb rw); 705170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); 706167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 707154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 708154941Sjhb __func__, rw); 709176017Sjeff#ifdef ADAPTIVE_RWLOCKS 710176017Sjeff spintries = 0; 711176017Sjeff#endif 712154941Sjhb } 713171516Sattilio lock_profile_obtain_lock_success(&rw->lock_object, contested, waittime, 714171516Sattilio file, line); 715154941Sjhb} 716154941Sjhb 717154941Sjhb/* 718154941Sjhb * This function is called if the first try at releasing a write lock failed. 719154941Sjhb * This means that one of the 2 waiter bits must be set indicating that at 720154941Sjhb * least one thread is waiting on this lock. 721154941Sjhb */ 722154941Sjhbvoid 723154941Sjhb_rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 724154941Sjhb{ 725154941Sjhb struct turnstile *ts; 726154941Sjhb uintptr_t v; 727154941Sjhb int queue; 728154941Sjhb 729171052Sattilio if (rw_wlocked(rw) && rw_recursed(rw)) { 730176017Sjeff rw->rw_recurse--; 731171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 732171052Sattilio CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); 733171052Sattilio return; 734171052Sattilio } 735176017Sjeff v = rw->rw_lock; 736171052Sattilio 737154941Sjhb KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), 738154941Sjhb ("%s: neither of the waiter flags are set", __func__)); 739154941Sjhb 740167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 741154941Sjhb CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); 742154941Sjhb 743170295Sjeff turnstile_chain_lock(&rw->lock_object); 744167787Sjhb ts = turnstile_lookup(&rw->lock_object); 745154941Sjhb MPASS(ts != NULL); 746154941Sjhb 747154941Sjhb /* 748154941Sjhb * Use the same algo as sx locks for now. Prefer waking up shared 749154941Sjhb * waiters if we have any over writers. This is probably not ideal. 750154941Sjhb * 751154941Sjhb * 'v' is the value we are going to write back to rw_lock. If we 752154941Sjhb * have waiters on both queues, we need to preserve the state of 753154941Sjhb * the waiter flag for the queue we don't wake up. For now this is 754154941Sjhb * hardcoded for the algorithm mentioned above. 755154941Sjhb * 756154941Sjhb * In the case of both readers and writers waiting we wakeup the 757154941Sjhb * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a 758154941Sjhb * new writer comes in before a reader it will claim the lock up 759154941Sjhb * above. There is probably a potential priority inversion in 760154941Sjhb * there that could be worked around either by waking both queues 761154941Sjhb * of waiters or doing some complicated lock handoff gymnastics. 762154941Sjhb */ 763157846Sjhb v = RW_UNLOCKED; 764176076Sjeff if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) { 765176076Sjeff queue = TS_EXCLUSIVE_QUEUE; 766176076Sjeff v |= (rw->rw_lock & RW_LOCK_READ_WAITERS); 767176076Sjeff } else 768154941Sjhb queue = TS_SHARED_QUEUE; 769157846Sjhb 770157846Sjhb /* Wake up all waiters for the specific queue. */ 771167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 772154941Sjhb CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, 773154941Sjhb queue == TS_SHARED_QUEUE ? "read" : "write"); 774154941Sjhb turnstile_broadcast(ts, queue); 775154941Sjhb atomic_store_rel_ptr(&rw->rw_lock, v); 776154941Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 777170295Sjeff turnstile_chain_unlock(&rw->lock_object); 778154941Sjhb} 779154941Sjhb 780157882Sjhb/* 781157882Sjhb * Attempt to do a non-blocking upgrade from a read lock to a write 782157882Sjhb * lock. This will only succeed if this thread holds a single read 783157882Sjhb * lock. Returns true if the upgrade succeeded and false otherwise. 784157882Sjhb */ 785157882Sjhbint 786157882Sjhb_rw_try_upgrade(struct rwlock *rw, const char *file, int line) 787157882Sjhb{ 788176017Sjeff uintptr_t v, x, tid; 789170295Sjeff struct turnstile *ts; 790157882Sjhb int success; 791157882Sjhb 792169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 793169394Sjhb ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); 794157882Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 795157882Sjhb 796157882Sjhb /* 797157882Sjhb * Attempt to switch from one reader to a writer. If there 798157882Sjhb * are any write waiters, then we will have to lock the 799157882Sjhb * turnstile first to prevent races with another writer 800157882Sjhb * calling turnstile_wait() before we have claimed this 801157882Sjhb * turnstile. So, do the simple case of no waiters first. 802157882Sjhb */ 803157882Sjhb tid = (uintptr_t)curthread; 804176017Sjeff success = 0; 805176017Sjeff for (;;) { 806176017Sjeff v = rw->rw_lock; 807176017Sjeff if (RW_READERS(v) > 1) 808176017Sjeff break; 809176017Sjeff if (!(v & RW_LOCK_WAITERS)) { 810176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid); 811176017Sjeff if (!success) 812176017Sjeff continue; 813176017Sjeff break; 814176017Sjeff } 815157882Sjhb 816176017Sjeff /* 817176017Sjeff * Ok, we think we have waiters, so lock the turnstile. 818176017Sjeff */ 819176017Sjeff ts = turnstile_trywait(&rw->lock_object); 820176017Sjeff v = rw->rw_lock; 821176017Sjeff if (RW_READERS(v) > 1) { 822176017Sjeff turnstile_cancel(ts); 823176017Sjeff break; 824176017Sjeff } 825176017Sjeff /* 826176017Sjeff * Try to switch from one reader to a writer again. This time 827176017Sjeff * we honor the current state of the waiters flags. 828176017Sjeff * If we obtain the lock with the flags set, then claim 829176017Sjeff * ownership of the turnstile. 830176017Sjeff */ 831176017Sjeff x = rw->rw_lock & RW_LOCK_WAITERS; 832176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x); 833176017Sjeff if (success) { 834176017Sjeff if (x) 835176017Sjeff turnstile_claim(ts); 836176017Sjeff else 837176017Sjeff turnstile_cancel(ts); 838176017Sjeff break; 839176017Sjeff } 840170295Sjeff turnstile_cancel(ts); 841176017Sjeff } 842167787Sjhb LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); 843176017Sjeff if (success) { 844176017Sjeff curthread->td_rw_rlocks--; 845167787Sjhb WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 846157882Sjhb file, line); 847176017Sjeff } 848157882Sjhb return (success); 849157882Sjhb} 850157882Sjhb 851157882Sjhb/* 852157882Sjhb * Downgrade a write lock into a single read lock. 853157882Sjhb */ 854157882Sjhbvoid 855157882Sjhb_rw_downgrade(struct rwlock *rw, const char *file, int line) 856157882Sjhb{ 857157882Sjhb struct turnstile *ts; 858157882Sjhb uintptr_t tid, v; 859176017Sjeff int rwait, wwait; 860157882Sjhb 861169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 862169394Sjhb ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); 863171052Sattilio _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); 864171052Sattilio#ifndef INVARIANTS 865171052Sattilio if (rw_recursed(rw)) 866171052Sattilio panic("downgrade of a recursed lock"); 867171052Sattilio#endif 868157882Sjhb 869167787Sjhb WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); 870157882Sjhb 871157882Sjhb /* 872157882Sjhb * Convert from a writer to a single reader. First we handle 873157882Sjhb * the easy case with no waiters. If there are any waiters, we 874176017Sjeff * lock the turnstile and "disown" the lock. 875157882Sjhb */ 876157882Sjhb tid = (uintptr_t)curthread; 877157882Sjhb if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) 878157882Sjhb goto out; 879157882Sjhb 880157882Sjhb /* 881157882Sjhb * Ok, we think we have waiters, so lock the turnstile so we can 882157882Sjhb * read the waiter flags without any races. 883157882Sjhb */ 884170295Sjeff turnstile_chain_lock(&rw->lock_object); 885176017Sjeff v = rw->rw_lock & RW_LOCK_WAITERS; 886176017Sjeff rwait = v & RW_LOCK_READ_WAITERS; 887176017Sjeff wwait = v & RW_LOCK_WRITE_WAITERS; 888176017Sjeff MPASS(rwait | wwait); 889157882Sjhb 890157882Sjhb /* 891176017Sjeff * Downgrade from a write lock while preserving waiters flag 892176017Sjeff * and give up ownership of the turnstile. 893157882Sjhb */ 894167787Sjhb ts = turnstile_lookup(&rw->lock_object); 895157882Sjhb MPASS(ts != NULL); 896176017Sjeff if (!wwait) 897176017Sjeff v &= ~RW_LOCK_READ_WAITERS; 898176017Sjeff atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v); 899176017Sjeff /* 900176017Sjeff * Wake other readers if there are no writers pending. Otherwise they 901176017Sjeff * won't be able to acquire the lock anyway. 902176017Sjeff */ 903176017Sjeff if (rwait && !wwait) { 904157882Sjhb turnstile_broadcast(ts, TS_SHARED_QUEUE); 905157882Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 906176017Sjeff } else 907157882Sjhb turnstile_disown(ts); 908170295Sjeff turnstile_chain_unlock(&rw->lock_object); 909157882Sjhbout: 910176017Sjeff curthread->td_rw_rlocks++; 911167787Sjhb LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); 912157882Sjhb} 913157882Sjhb 914154941Sjhb#ifdef INVARIANT_SUPPORT 915155162Sscottl#ifndef INVARIANTS 916154941Sjhb#undef _rw_assert 917154941Sjhb#endif 918154941Sjhb 919154941Sjhb/* 920154941Sjhb * In the non-WITNESS case, rw_assert() can only detect that at least 921154941Sjhb * *some* thread owns an rlock, but it cannot guarantee that *this* 922154941Sjhb * thread owns an rlock. 923154941Sjhb */ 924154941Sjhbvoid 925154941Sjhb_rw_assert(struct rwlock *rw, int what, const char *file, int line) 926154941Sjhb{ 927154941Sjhb 928154941Sjhb if (panicstr != NULL) 929154941Sjhb return; 930154941Sjhb switch (what) { 931154941Sjhb case RA_LOCKED: 932171052Sattilio case RA_LOCKED | RA_RECURSED: 933171052Sattilio case RA_LOCKED | RA_NOTRECURSED: 934154941Sjhb case RA_RLOCKED: 935154941Sjhb#ifdef WITNESS 936167787Sjhb witness_assert(&rw->lock_object, what, file, line); 937154941Sjhb#else 938154941Sjhb /* 939154941Sjhb * If some other thread has a write lock or we have one 940154941Sjhb * and are asserting a read lock, fail. Also, if no one 941154941Sjhb * has a lock at all, fail. 942154941Sjhb */ 943155061Sscottl if (rw->rw_lock == RW_UNLOCKED || 944155061Sscottl (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || 945157826Sjhb rw_wowner(rw) != curthread))) 946154941Sjhb panic("Lock %s not %slocked @ %s:%d\n", 947167787Sjhb rw->lock_object.lo_name, (what == RA_RLOCKED) ? 948154941Sjhb "read " : "", file, line); 949171052Sattilio 950171052Sattilio if (!(rw->rw_lock & RW_LOCK_READ)) { 951171052Sattilio if (rw_recursed(rw)) { 952171052Sattilio if (what & RA_NOTRECURSED) 953171052Sattilio panic("Lock %s recursed @ %s:%d\n", 954171052Sattilio rw->lock_object.lo_name, file, 955171052Sattilio line); 956171052Sattilio } else if (what & RA_RECURSED) 957171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 958171052Sattilio rw->lock_object.lo_name, file, line); 959171052Sattilio } 960154941Sjhb#endif 961154941Sjhb break; 962154941Sjhb case RA_WLOCKED: 963171052Sattilio case RA_WLOCKED | RA_RECURSED: 964171052Sattilio case RA_WLOCKED | RA_NOTRECURSED: 965157826Sjhb if (rw_wowner(rw) != curthread) 966154941Sjhb panic("Lock %s not exclusively locked @ %s:%d\n", 967167787Sjhb rw->lock_object.lo_name, file, line); 968171052Sattilio if (rw_recursed(rw)) { 969171052Sattilio if (what & RA_NOTRECURSED) 970171052Sattilio panic("Lock %s recursed @ %s:%d\n", 971171052Sattilio rw->lock_object.lo_name, file, line); 972171052Sattilio } else if (what & RA_RECURSED) 973171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 974171052Sattilio rw->lock_object.lo_name, file, line); 975154941Sjhb break; 976154941Sjhb case RA_UNLOCKED: 977154941Sjhb#ifdef WITNESS 978167787Sjhb witness_assert(&rw->lock_object, what, file, line); 979154941Sjhb#else 980154941Sjhb /* 981154941Sjhb * If we hold a write lock fail. We can't reliably check 982154941Sjhb * to see if we hold a read lock or not. 983154941Sjhb */ 984157826Sjhb if (rw_wowner(rw) == curthread) 985154941Sjhb panic("Lock %s exclusively locked @ %s:%d\n", 986167787Sjhb rw->lock_object.lo_name, file, line); 987154941Sjhb#endif 988154941Sjhb break; 989154941Sjhb default: 990154941Sjhb panic("Unknown rw lock assertion: %d @ %s:%d", what, file, 991154941Sjhb line); 992154941Sjhb } 993154941Sjhb} 994154941Sjhb#endif /* INVARIANT_SUPPORT */ 995154941Sjhb 996154941Sjhb#ifdef DDB 997154941Sjhbvoid 998154941Sjhbdb_show_rwlock(struct lock_object *lock) 999154941Sjhb{ 1000154941Sjhb struct rwlock *rw; 1001154941Sjhb struct thread *td; 1002154941Sjhb 1003154941Sjhb rw = (struct rwlock *)lock; 1004154941Sjhb 1005154941Sjhb db_printf(" state: "); 1006154941Sjhb if (rw->rw_lock == RW_UNLOCKED) 1007154941Sjhb db_printf("UNLOCKED\n"); 1008169394Sjhb else if (rw->rw_lock == RW_DESTROYED) { 1009169394Sjhb db_printf("DESTROYED\n"); 1010169394Sjhb return; 1011169394Sjhb } else if (rw->rw_lock & RW_LOCK_READ) 1012167504Sjhb db_printf("RLOCK: %ju locks\n", 1013167504Sjhb (uintmax_t)(RW_READERS(rw->rw_lock))); 1014154941Sjhb else { 1015157826Sjhb td = rw_wowner(rw); 1016154941Sjhb db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1017173600Sjulian td->td_tid, td->td_proc->p_pid, td->td_name); 1018171052Sattilio if (rw_recursed(rw)) 1019171052Sattilio db_printf(" recursed: %u\n", rw->rw_recurse); 1020154941Sjhb } 1021154941Sjhb db_printf(" waiters: "); 1022154941Sjhb switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { 1023154941Sjhb case RW_LOCK_READ_WAITERS: 1024154941Sjhb db_printf("readers\n"); 1025154941Sjhb break; 1026154941Sjhb case RW_LOCK_WRITE_WAITERS: 1027154941Sjhb db_printf("writers\n"); 1028154941Sjhb break; 1029154941Sjhb case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: 1030167492Sjhb db_printf("readers and writers\n"); 1031154941Sjhb break; 1032154941Sjhb default: 1033154941Sjhb db_printf("none\n"); 1034154941Sjhb break; 1035154941Sjhb } 1036154941Sjhb} 1037154941Sjhb 1038154941Sjhb#endif 1039