kern_rwlock.c revision 189846
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 189846 2009-03-15 08:03:54Z jeff $"); 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 285189846Sjeff#ifdef LOCK_PROFILING 286167307Sjhb uint64_t waittime = 0; 287167054Skmacy int contested = 0; 288189846Sjeff#endif 289176017Sjeff uintptr_t v; 290154941Sjhb 291169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 292169394Sjhb ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); 293157826Sjhb KASSERT(rw_wowner(rw) != curthread, 294154941Sjhb ("%s (%s): wlock already held @ %s:%d", __func__, 295167787Sjhb rw->lock_object.lo_name, file, line)); 296182914Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); 297154941Sjhb 298154941Sjhb for (;;) { 299154941Sjhb /* 300154941Sjhb * Handle the easy case. If no other thread has a write 301154941Sjhb * lock, then try to bump up the count of read locks. Note 302154941Sjhb * that we have to preserve the current state of the 303154941Sjhb * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a 304154941Sjhb * read lock, then rw_lock must have changed, so restart 305154941Sjhb * the loop. Note that this handles the case of a 306154941Sjhb * completely unlocked rwlock since such a lock is encoded 307154941Sjhb * as a read lock with no waiters. 308154941Sjhb */ 309176017Sjeff v = rw->rw_lock; 310176017Sjeff if (RW_CAN_READ(v)) { 311154941Sjhb /* 312154941Sjhb * The RW_LOCK_READ_WAITERS flag should only be set 313176017Sjeff * if the lock has been unlocked and write waiters 314176017Sjeff * were present. 315154941Sjhb */ 316176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, 317176017Sjeff v + RW_ONE_READER)) { 318167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 319154941Sjhb CTR4(KTR_LOCK, 320154941Sjhb "%s: %p succeed %p -> %p", __func__, 321176017Sjeff rw, (void *)v, 322176017Sjeff (void *)(v + RW_ONE_READER)); 323154941Sjhb break; 324154941Sjhb } 325157846Sjhb cpu_spinwait(); 326154941Sjhb continue; 327154941Sjhb } 328174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 329174629Sjeff &contested, &waittime); 330154941Sjhb 331173960Sattilio#ifdef ADAPTIVE_RWLOCKS 332154941Sjhb /* 333173960Sattilio * If the owner is running on another CPU, spin until 334173960Sattilio * the owner stops running or the state of the lock 335173960Sattilio * changes. 336173960Sattilio */ 337176017Sjeff if ((v & RW_LOCK_READ) == 0) { 338176017Sjeff owner = (struct thread *)RW_OWNER(v); 339176017Sjeff if (TD_IS_RUNNING(owner)) { 340176017Sjeff if (LOCK_LOG_TEST(&rw->lock_object, 0)) 341176017Sjeff CTR3(KTR_LOCK, 342176017Sjeff "%s: spinning on %p held by %p", 343176017Sjeff __func__, rw, owner); 344176017Sjeff while ((struct thread*)RW_OWNER(rw->rw_lock) == 345176017Sjeff owner && TD_IS_RUNNING(owner)) 346176017Sjeff cpu_spinwait(); 347176017Sjeff continue; 348176017Sjeff } 349177912Sjeff } else if (spintries < rowner_retries) { 350177912Sjeff spintries++; 351177912Sjeff for (i = 0; i < rowner_loops; i++) { 352177912Sjeff v = rw->rw_lock; 353177912Sjeff if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) 354177912Sjeff break; 355177912Sjeff cpu_spinwait(); 356177912Sjeff } 357177912Sjeff if (i != rowner_loops) 358177912Sjeff continue; 359173960Sattilio } 360173960Sattilio#endif 361173960Sattilio 362173960Sattilio /* 363154941Sjhb * Okay, now it's the hard case. Some other thread already 364176017Sjeff * has a write lock or there are write waiters present, 365176017Sjeff * acquire the turnstile lock so we can begin the process 366176017Sjeff * of blocking. 367154941Sjhb */ 368170295Sjeff ts = turnstile_trywait(&rw->lock_object); 369154941Sjhb 370154941Sjhb /* 371154941Sjhb * The lock might have been released while we spun, so 372176017Sjeff * recheck its state and restart the loop if needed. 373154941Sjhb */ 374176017Sjeff v = rw->rw_lock; 375176017Sjeff if (RW_CAN_READ(v)) { 376170295Sjeff turnstile_cancel(ts); 377157846Sjhb cpu_spinwait(); 378154941Sjhb continue; 379154941Sjhb } 380154941Sjhb 381173960Sattilio#ifdef ADAPTIVE_RWLOCKS 382154941Sjhb /* 383173960Sattilio * If the current owner of the lock is executing on another 384173960Sattilio * CPU quit the hard path and try to spin. 385173960Sattilio */ 386176017Sjeff if ((v & RW_LOCK_READ) == 0) { 387176017Sjeff owner = (struct thread *)RW_OWNER(v); 388176017Sjeff if (TD_IS_RUNNING(owner)) { 389176017Sjeff turnstile_cancel(ts); 390176017Sjeff cpu_spinwait(); 391176017Sjeff continue; 392176017Sjeff } 393173960Sattilio } 394173960Sattilio#endif 395173960Sattilio 396173960Sattilio /* 397176017Sjeff * The lock is held in write mode or it already has waiters. 398154941Sjhb */ 399176017Sjeff MPASS(!RW_CAN_READ(v)); 400176017Sjeff 401176017Sjeff /* 402176017Sjeff * If the RW_LOCK_READ_WAITERS flag is already set, then 403176017Sjeff * we can go ahead and block. If it is not set then try 404176017Sjeff * to set it. If we fail to set it drop the turnstile 405176017Sjeff * lock and restart the loop. 406176017Sjeff */ 407176017Sjeff if (!(v & RW_LOCK_READ_WAITERS)) { 408176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 409176017Sjeff v | RW_LOCK_READ_WAITERS)) { 410170295Sjeff turnstile_cancel(ts); 411157826Sjhb cpu_spinwait(); 412157826Sjhb continue; 413157826Sjhb } 414167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 415157826Sjhb CTR2(KTR_LOCK, "%s: %p set read waiters flag", 416157826Sjhb __func__, rw); 417154941Sjhb } 418154941Sjhb 419154941Sjhb /* 420154941Sjhb * We were unable to acquire the lock and the read waiters 421154941Sjhb * flag is set, so we must block on the turnstile. 422154941Sjhb */ 423167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 424154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 425154941Sjhb rw); 426170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); 427167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 428154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 429154941Sjhb __func__, rw); 430154941Sjhb } 431154941Sjhb 432154941Sjhb /* 433154941Sjhb * TODO: acquire "owner of record" here. Here be turnstile dragons 434154941Sjhb * however. turnstiles don't like owners changing between calls to 435154941Sjhb * turnstile_wait() currently. 436154941Sjhb */ 437174629Sjeff lock_profile_obtain_lock_success( &rw->lock_object, contested, 438174629Sjeff waittime, file, line); 439167787Sjhb LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); 440167787Sjhb WITNESS_LOCK(&rw->lock_object, 0, file, line); 441160771Sjhb curthread->td_locks++; 442176017Sjeff curthread->td_rw_rlocks++; 443154941Sjhb} 444154941Sjhb 445177843Sattilioint 446177843Sattilio_rw_try_rlock(struct rwlock *rw, const char *file, int line) 447177843Sattilio{ 448177843Sattilio uintptr_t x; 449177843Sattilio 450177843Sattilio for (;;) { 451177843Sattilio x = rw->rw_lock; 452177843Sattilio KASSERT(rw->rw_lock != RW_DESTROYED, 453177843Sattilio ("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line)); 454177843Sattilio if (!(x & RW_LOCK_READ)) 455177843Sattilio break; 456177843Sattilio if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) { 457177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file, 458177843Sattilio line); 459177843Sattilio WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line); 460177843Sattilio curthread->td_locks++; 461177843Sattilio curthread->td_rw_rlocks++; 462177843Sattilio return (1); 463177843Sattilio } 464177843Sattilio } 465177843Sattilio 466177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line); 467177843Sattilio return (0); 468177843Sattilio} 469177843Sattilio 470154941Sjhbvoid 471154941Sjhb_rw_runlock(struct rwlock *rw, const char *file, int line) 472154941Sjhb{ 473154941Sjhb struct turnstile *ts; 474176017Sjeff uintptr_t x, v, queue; 475154941Sjhb 476169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 477169394Sjhb ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); 478154941Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 479160771Sjhb curthread->td_locks--; 480176017Sjeff curthread->td_rw_rlocks--; 481167787Sjhb WITNESS_UNLOCK(&rw->lock_object, 0, file, line); 482167787Sjhb LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); 483154941Sjhb 484154941Sjhb /* TODO: drop "owner of record" here. */ 485154941Sjhb 486154941Sjhb for (;;) { 487154941Sjhb /* 488154941Sjhb * See if there is more than one read lock held. If so, 489154941Sjhb * just drop one and return. 490154941Sjhb */ 491154941Sjhb x = rw->rw_lock; 492154941Sjhb if (RW_READERS(x) > 1) { 493154941Sjhb if (atomic_cmpset_ptr(&rw->rw_lock, x, 494154941Sjhb x - RW_ONE_READER)) { 495167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 496154941Sjhb CTR4(KTR_LOCK, 497154941Sjhb "%s: %p succeeded %p -> %p", 498154941Sjhb __func__, rw, (void *)x, 499154941Sjhb (void *)(x - RW_ONE_READER)); 500154941Sjhb break; 501154941Sjhb } 502154941Sjhb continue; 503167307Sjhb } 504154941Sjhb /* 505154941Sjhb * If there aren't any waiters for a write lock, then try 506154941Sjhb * to drop it quickly. 507154941Sjhb */ 508176017Sjeff if (!(x & RW_LOCK_WAITERS)) { 509176017Sjeff MPASS((x & ~RW_LOCK_WRITE_SPINNER) == 510176017Sjeff RW_READERS_LOCK(1)); 511176017Sjeff if (atomic_cmpset_ptr(&rw->rw_lock, x, RW_UNLOCKED)) { 512167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 513154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded", 514154941Sjhb __func__, rw); 515154941Sjhb break; 516154941Sjhb } 517154941Sjhb continue; 518154941Sjhb } 519154941Sjhb /* 520176017Sjeff * Ok, we know we have waiters and we think we are the 521176017Sjeff * last reader, so grab the turnstile lock. 522154941Sjhb */ 523170295Sjeff turnstile_chain_lock(&rw->lock_object); 524176017Sjeff v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 525176017Sjeff MPASS(v & RW_LOCK_WAITERS); 526154941Sjhb 527154941Sjhb /* 528154941Sjhb * Try to drop our lock leaving the lock in a unlocked 529154941Sjhb * state. 530154941Sjhb * 531154941Sjhb * If you wanted to do explicit lock handoff you'd have to 532154941Sjhb * do it here. You'd also want to use turnstile_signal() 533154941Sjhb * and you'd have to handle the race where a higher 534154941Sjhb * priority thread blocks on the write lock before the 535154941Sjhb * thread you wakeup actually runs and have the new thread 536154941Sjhb * "steal" the lock. For now it's a lot simpler to just 537154941Sjhb * wakeup all of the waiters. 538154941Sjhb * 539154941Sjhb * As above, if we fail, then another thread might have 540154941Sjhb * acquired a read lock, so drop the turnstile lock and 541154941Sjhb * restart. 542154941Sjhb */ 543176017Sjeff x = RW_UNLOCKED; 544176017Sjeff if (v & RW_LOCK_WRITE_WAITERS) { 545176017Sjeff queue = TS_EXCLUSIVE_QUEUE; 546176017Sjeff x |= (v & RW_LOCK_READ_WAITERS); 547176017Sjeff } else 548176017Sjeff queue = TS_SHARED_QUEUE; 549176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, 550176017Sjeff x)) { 551170295Sjeff turnstile_chain_unlock(&rw->lock_object); 552154941Sjhb continue; 553154941Sjhb } 554167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 555154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", 556154941Sjhb __func__, rw); 557154941Sjhb 558154941Sjhb /* 559154941Sjhb * Ok. The lock is released and all that's left is to 560154941Sjhb * wake up the waiters. Note that the lock might not be 561154941Sjhb * free anymore, but in that case the writers will just 562154941Sjhb * block again if they run before the new lock holder(s) 563154941Sjhb * release the lock. 564154941Sjhb */ 565167787Sjhb ts = turnstile_lookup(&rw->lock_object); 566157846Sjhb MPASS(ts != NULL); 567176017Sjeff turnstile_broadcast(ts, queue); 568154941Sjhb turnstile_unpend(ts, TS_SHARED_LOCK); 569170295Sjeff turnstile_chain_unlock(&rw->lock_object); 570154941Sjhb break; 571154941Sjhb } 572174629Sjeff lock_profile_release_lock(&rw->lock_object); 573154941Sjhb} 574154941Sjhb 575154941Sjhb/* 576154941Sjhb * This function is called when we are unable to obtain a write lock on the 577154941Sjhb * first try. This means that at least one other thread holds either a 578154941Sjhb * read or write lock. 579154941Sjhb */ 580154941Sjhbvoid 581154941Sjhb_rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 582154941Sjhb{ 583170295Sjeff struct turnstile *ts; 584167801Sjhb#ifdef ADAPTIVE_RWLOCKS 585157846Sjhb volatile struct thread *owner; 586176017Sjeff int spintries = 0; 587176017Sjeff int i; 588157851Swkoszek#endif 589189846Sjeff uintptr_t v, x; 590189846Sjeff#ifdef LOCK_PROFILING 591171516Sattilio uint64_t waittime = 0; 592171516Sattilio int contested = 0; 593189846Sjeff#endif 594154941Sjhb 595171052Sattilio if (rw_wlocked(rw)) { 596171052Sattilio KASSERT(rw->lock_object.lo_flags & RW_RECURSE, 597171052Sattilio ("%s: recursing but non-recursive rw %s @ %s:%d\n", 598171052Sattilio __func__, rw->lock_object.lo_name, file, line)); 599171052Sattilio rw->rw_recurse++; 600171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 601171052Sattilio CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); 602171052Sattilio return; 603171052Sattilio } 604171052Sattilio 605167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 606154941Sjhb CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 607167787Sjhb rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); 608154941Sjhb 609154941Sjhb while (!_rw_write_lock(rw, tid)) { 610174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 611174629Sjeff &contested, &waittime); 612173960Sattilio#ifdef ADAPTIVE_RWLOCKS 613173960Sattilio /* 614173960Sattilio * If the lock is write locked and the owner is 615173960Sattilio * running on another CPU, spin until the owner stops 616173960Sattilio * running or the state of the lock changes. 617173960Sattilio */ 618173960Sattilio v = rw->rw_lock; 619173960Sattilio owner = (struct thread *)RW_OWNER(v); 620173960Sattilio if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { 621173960Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 622173960Sattilio CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 623173960Sattilio __func__, rw, owner); 624173960Sattilio while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && 625173960Sattilio TD_IS_RUNNING(owner)) 626173960Sattilio cpu_spinwait(); 627173960Sattilio continue; 628173960Sattilio } 629177912Sjeff if ((v & RW_LOCK_READ) && RW_READERS(v) && 630177912Sjeff spintries < rowner_retries) { 631176017Sjeff if (!(v & RW_LOCK_WRITE_SPINNER)) { 632176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 633176017Sjeff v | RW_LOCK_WRITE_SPINNER)) { 634176017Sjeff cpu_spinwait(); 635176017Sjeff continue; 636176017Sjeff } 637176017Sjeff } 638176017Sjeff spintries++; 639177912Sjeff for (i = 0; i < rowner_loops; i++) { 640176017Sjeff if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) 641176017Sjeff break; 642176017Sjeff cpu_spinwait(); 643176017Sjeff } 644177912Sjeff if (i != rowner_loops) 645176017Sjeff continue; 646176017Sjeff } 647173960Sattilio#endif 648170295Sjeff ts = turnstile_trywait(&rw->lock_object); 649154941Sjhb v = rw->rw_lock; 650154941Sjhb 651173960Sattilio#ifdef ADAPTIVE_RWLOCKS 652154941Sjhb /* 653173960Sattilio * If the current owner of the lock is executing on another 654173960Sattilio * CPU quit the hard path and try to spin. 655173960Sattilio */ 656173960Sattilio if (!(v & RW_LOCK_READ)) { 657173960Sattilio owner = (struct thread *)RW_OWNER(v); 658173960Sattilio if (TD_IS_RUNNING(owner)) { 659173960Sattilio turnstile_cancel(ts); 660173960Sattilio cpu_spinwait(); 661173960Sattilio continue; 662173960Sattilio } 663173960Sattilio } 664173960Sattilio#endif 665173960Sattilio /* 666179334Sattilio * Check for the waiters flags about this rwlock. 667179334Sattilio * If the lock was released, without maintain any pending 668179334Sattilio * waiters queue, simply try to acquire it. 669179334Sattilio * If a pending waiters queue is present, claim the lock 670179334Sattilio * ownership and maintain the pending queue. 671154941Sjhb */ 672176017Sjeff x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 673176017Sjeff if ((v & ~x) == RW_UNLOCKED) { 674176017Sjeff x &= ~RW_LOCK_WRITE_SPINNER; 675176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) { 676176017Sjeff if (x) 677176017Sjeff turnstile_claim(ts); 678176017Sjeff else 679176017Sjeff turnstile_cancel(ts); 680154941Sjhb break; 681154941Sjhb } 682170295Sjeff turnstile_cancel(ts); 683154941Sjhb cpu_spinwait(); 684154941Sjhb continue; 685154941Sjhb } 686154941Sjhb /* 687154941Sjhb * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to 688154941Sjhb * set it. If we fail to set it, then loop back and try 689154941Sjhb * again. 690154941Sjhb */ 691157826Sjhb if (!(v & RW_LOCK_WRITE_WAITERS)) { 692157826Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, v, 693157826Sjhb v | RW_LOCK_WRITE_WAITERS)) { 694170295Sjeff turnstile_cancel(ts); 695157826Sjhb cpu_spinwait(); 696157826Sjhb continue; 697157826Sjhb } 698167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 699157826Sjhb CTR2(KTR_LOCK, "%s: %p set write waiters flag", 700157826Sjhb __func__, rw); 701154941Sjhb } 702157846Sjhb /* 703154941Sjhb * We were unable to acquire the lock and the write waiters 704154941Sjhb * flag is set, so we must block on the turnstile. 705154941Sjhb */ 706167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 707154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 708154941Sjhb rw); 709170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); 710167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 711154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 712154941Sjhb __func__, rw); 713176017Sjeff#ifdef ADAPTIVE_RWLOCKS 714176017Sjeff spintries = 0; 715176017Sjeff#endif 716154941Sjhb } 717171516Sattilio lock_profile_obtain_lock_success(&rw->lock_object, contested, waittime, 718171516Sattilio file, line); 719154941Sjhb} 720154941Sjhb 721154941Sjhb/* 722154941Sjhb * This function is called if the first try at releasing a write lock failed. 723154941Sjhb * This means that one of the 2 waiter bits must be set indicating that at 724154941Sjhb * least one thread is waiting on this lock. 725154941Sjhb */ 726154941Sjhbvoid 727154941Sjhb_rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 728154941Sjhb{ 729154941Sjhb struct turnstile *ts; 730154941Sjhb uintptr_t v; 731154941Sjhb int queue; 732154941Sjhb 733171052Sattilio if (rw_wlocked(rw) && rw_recursed(rw)) { 734176017Sjeff rw->rw_recurse--; 735171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 736171052Sattilio CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); 737171052Sattilio return; 738171052Sattilio } 739171052Sattilio 740154941Sjhb KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), 741154941Sjhb ("%s: neither of the waiter flags are set", __func__)); 742154941Sjhb 743167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 744154941Sjhb CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); 745154941Sjhb 746170295Sjeff turnstile_chain_lock(&rw->lock_object); 747167787Sjhb ts = turnstile_lookup(&rw->lock_object); 748154941Sjhb MPASS(ts != NULL); 749154941Sjhb 750154941Sjhb /* 751154941Sjhb * Use the same algo as sx locks for now. Prefer waking up shared 752154941Sjhb * waiters if we have any over writers. This is probably not ideal. 753154941Sjhb * 754154941Sjhb * 'v' is the value we are going to write back to rw_lock. If we 755154941Sjhb * have waiters on both queues, we need to preserve the state of 756154941Sjhb * the waiter flag for the queue we don't wake up. For now this is 757154941Sjhb * hardcoded for the algorithm mentioned above. 758154941Sjhb * 759154941Sjhb * In the case of both readers and writers waiting we wakeup the 760154941Sjhb * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a 761154941Sjhb * new writer comes in before a reader it will claim the lock up 762154941Sjhb * above. There is probably a potential priority inversion in 763154941Sjhb * there that could be worked around either by waking both queues 764154941Sjhb * of waiters or doing some complicated lock handoff gymnastics. 765154941Sjhb */ 766157846Sjhb v = RW_UNLOCKED; 767176076Sjeff if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) { 768176076Sjeff queue = TS_EXCLUSIVE_QUEUE; 769176076Sjeff v |= (rw->rw_lock & RW_LOCK_READ_WAITERS); 770176076Sjeff } else 771154941Sjhb queue = TS_SHARED_QUEUE; 772157846Sjhb 773157846Sjhb /* Wake up all waiters for the specific queue. */ 774167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 775154941Sjhb CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, 776154941Sjhb queue == TS_SHARED_QUEUE ? "read" : "write"); 777154941Sjhb turnstile_broadcast(ts, queue); 778154941Sjhb atomic_store_rel_ptr(&rw->rw_lock, v); 779154941Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 780170295Sjeff turnstile_chain_unlock(&rw->lock_object); 781154941Sjhb} 782154941Sjhb 783157882Sjhb/* 784157882Sjhb * Attempt to do a non-blocking upgrade from a read lock to a write 785157882Sjhb * lock. This will only succeed if this thread holds a single read 786157882Sjhb * lock. Returns true if the upgrade succeeded and false otherwise. 787157882Sjhb */ 788157882Sjhbint 789157882Sjhb_rw_try_upgrade(struct rwlock *rw, const char *file, int line) 790157882Sjhb{ 791176017Sjeff uintptr_t v, x, tid; 792170295Sjeff struct turnstile *ts; 793157882Sjhb int success; 794157882Sjhb 795169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 796169394Sjhb ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); 797157882Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 798157882Sjhb 799157882Sjhb /* 800157882Sjhb * Attempt to switch from one reader to a writer. If there 801157882Sjhb * are any write waiters, then we will have to lock the 802157882Sjhb * turnstile first to prevent races with another writer 803157882Sjhb * calling turnstile_wait() before we have claimed this 804157882Sjhb * turnstile. So, do the simple case of no waiters first. 805157882Sjhb */ 806157882Sjhb tid = (uintptr_t)curthread; 807176017Sjeff success = 0; 808176017Sjeff for (;;) { 809176017Sjeff v = rw->rw_lock; 810176017Sjeff if (RW_READERS(v) > 1) 811176017Sjeff break; 812176017Sjeff if (!(v & RW_LOCK_WAITERS)) { 813176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid); 814176017Sjeff if (!success) 815176017Sjeff continue; 816176017Sjeff break; 817176017Sjeff } 818157882Sjhb 819176017Sjeff /* 820176017Sjeff * Ok, we think we have waiters, so lock the turnstile. 821176017Sjeff */ 822176017Sjeff ts = turnstile_trywait(&rw->lock_object); 823176017Sjeff v = rw->rw_lock; 824176017Sjeff if (RW_READERS(v) > 1) { 825176017Sjeff turnstile_cancel(ts); 826176017Sjeff break; 827176017Sjeff } 828176017Sjeff /* 829176017Sjeff * Try to switch from one reader to a writer again. This time 830176017Sjeff * we honor the current state of the waiters flags. 831176017Sjeff * If we obtain the lock with the flags set, then claim 832176017Sjeff * ownership of the turnstile. 833176017Sjeff */ 834176017Sjeff x = rw->rw_lock & RW_LOCK_WAITERS; 835176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x); 836176017Sjeff if (success) { 837176017Sjeff if (x) 838176017Sjeff turnstile_claim(ts); 839176017Sjeff else 840176017Sjeff turnstile_cancel(ts); 841176017Sjeff break; 842176017Sjeff } 843170295Sjeff turnstile_cancel(ts); 844176017Sjeff } 845167787Sjhb LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); 846176017Sjeff if (success) { 847176017Sjeff curthread->td_rw_rlocks--; 848167787Sjhb WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 849157882Sjhb file, line); 850176017Sjeff } 851157882Sjhb return (success); 852157882Sjhb} 853157882Sjhb 854157882Sjhb/* 855157882Sjhb * Downgrade a write lock into a single read lock. 856157882Sjhb */ 857157882Sjhbvoid 858157882Sjhb_rw_downgrade(struct rwlock *rw, const char *file, int line) 859157882Sjhb{ 860157882Sjhb struct turnstile *ts; 861157882Sjhb uintptr_t tid, v; 862176017Sjeff int rwait, wwait; 863157882Sjhb 864169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 865169394Sjhb ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); 866171052Sattilio _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); 867171052Sattilio#ifndef INVARIANTS 868171052Sattilio if (rw_recursed(rw)) 869171052Sattilio panic("downgrade of a recursed lock"); 870171052Sattilio#endif 871157882Sjhb 872167787Sjhb WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); 873157882Sjhb 874157882Sjhb /* 875157882Sjhb * Convert from a writer to a single reader. First we handle 876157882Sjhb * the easy case with no waiters. If there are any waiters, we 877176017Sjeff * lock the turnstile and "disown" the lock. 878157882Sjhb */ 879157882Sjhb tid = (uintptr_t)curthread; 880157882Sjhb if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) 881157882Sjhb goto out; 882157882Sjhb 883157882Sjhb /* 884157882Sjhb * Ok, we think we have waiters, so lock the turnstile so we can 885157882Sjhb * read the waiter flags without any races. 886157882Sjhb */ 887170295Sjeff turnstile_chain_lock(&rw->lock_object); 888176017Sjeff v = rw->rw_lock & RW_LOCK_WAITERS; 889176017Sjeff rwait = v & RW_LOCK_READ_WAITERS; 890176017Sjeff wwait = v & RW_LOCK_WRITE_WAITERS; 891176017Sjeff MPASS(rwait | wwait); 892157882Sjhb 893157882Sjhb /* 894176017Sjeff * Downgrade from a write lock while preserving waiters flag 895176017Sjeff * and give up ownership of the turnstile. 896157882Sjhb */ 897167787Sjhb ts = turnstile_lookup(&rw->lock_object); 898157882Sjhb MPASS(ts != NULL); 899176017Sjeff if (!wwait) 900176017Sjeff v &= ~RW_LOCK_READ_WAITERS; 901176017Sjeff atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v); 902176017Sjeff /* 903176017Sjeff * Wake other readers if there are no writers pending. Otherwise they 904176017Sjeff * won't be able to acquire the lock anyway. 905176017Sjeff */ 906176017Sjeff if (rwait && !wwait) { 907157882Sjhb turnstile_broadcast(ts, TS_SHARED_QUEUE); 908157882Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 909176017Sjeff } else 910157882Sjhb turnstile_disown(ts); 911170295Sjeff turnstile_chain_unlock(&rw->lock_object); 912157882Sjhbout: 913176017Sjeff curthread->td_rw_rlocks++; 914167787Sjhb LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); 915157882Sjhb} 916157882Sjhb 917154941Sjhb#ifdef INVARIANT_SUPPORT 918155162Sscottl#ifndef INVARIANTS 919154941Sjhb#undef _rw_assert 920154941Sjhb#endif 921154941Sjhb 922154941Sjhb/* 923154941Sjhb * In the non-WITNESS case, rw_assert() can only detect that at least 924154941Sjhb * *some* thread owns an rlock, but it cannot guarantee that *this* 925154941Sjhb * thread owns an rlock. 926154941Sjhb */ 927154941Sjhbvoid 928154941Sjhb_rw_assert(struct rwlock *rw, int what, const char *file, int line) 929154941Sjhb{ 930154941Sjhb 931154941Sjhb if (panicstr != NULL) 932154941Sjhb return; 933154941Sjhb switch (what) { 934154941Sjhb case RA_LOCKED: 935171052Sattilio case RA_LOCKED | RA_RECURSED: 936171052Sattilio case RA_LOCKED | RA_NOTRECURSED: 937154941Sjhb case RA_RLOCKED: 938154941Sjhb#ifdef WITNESS 939167787Sjhb witness_assert(&rw->lock_object, what, file, line); 940154941Sjhb#else 941154941Sjhb /* 942154941Sjhb * If some other thread has a write lock or we have one 943154941Sjhb * and are asserting a read lock, fail. Also, if no one 944154941Sjhb * has a lock at all, fail. 945154941Sjhb */ 946155061Sscottl if (rw->rw_lock == RW_UNLOCKED || 947155061Sscottl (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || 948157826Sjhb rw_wowner(rw) != curthread))) 949154941Sjhb panic("Lock %s not %slocked @ %s:%d\n", 950167787Sjhb rw->lock_object.lo_name, (what == RA_RLOCKED) ? 951154941Sjhb "read " : "", file, line); 952171052Sattilio 953171052Sattilio if (!(rw->rw_lock & RW_LOCK_READ)) { 954171052Sattilio if (rw_recursed(rw)) { 955171052Sattilio if (what & RA_NOTRECURSED) 956171052Sattilio panic("Lock %s recursed @ %s:%d\n", 957171052Sattilio rw->lock_object.lo_name, file, 958171052Sattilio line); 959171052Sattilio } else if (what & RA_RECURSED) 960171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 961171052Sattilio rw->lock_object.lo_name, file, line); 962171052Sattilio } 963154941Sjhb#endif 964154941Sjhb break; 965154941Sjhb case RA_WLOCKED: 966171052Sattilio case RA_WLOCKED | RA_RECURSED: 967171052Sattilio case RA_WLOCKED | RA_NOTRECURSED: 968157826Sjhb if (rw_wowner(rw) != curthread) 969154941Sjhb panic("Lock %s not exclusively locked @ %s:%d\n", 970167787Sjhb rw->lock_object.lo_name, file, line); 971171052Sattilio if (rw_recursed(rw)) { 972171052Sattilio if (what & RA_NOTRECURSED) 973171052Sattilio panic("Lock %s recursed @ %s:%d\n", 974171052Sattilio rw->lock_object.lo_name, file, line); 975171052Sattilio } else if (what & RA_RECURSED) 976171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 977171052Sattilio rw->lock_object.lo_name, file, line); 978154941Sjhb break; 979154941Sjhb case RA_UNLOCKED: 980154941Sjhb#ifdef WITNESS 981167787Sjhb witness_assert(&rw->lock_object, what, file, line); 982154941Sjhb#else 983154941Sjhb /* 984154941Sjhb * If we hold a write lock fail. We can't reliably check 985154941Sjhb * to see if we hold a read lock or not. 986154941Sjhb */ 987157826Sjhb if (rw_wowner(rw) == curthread) 988154941Sjhb panic("Lock %s exclusively locked @ %s:%d\n", 989167787Sjhb rw->lock_object.lo_name, file, line); 990154941Sjhb#endif 991154941Sjhb break; 992154941Sjhb default: 993154941Sjhb panic("Unknown rw lock assertion: %d @ %s:%d", what, file, 994154941Sjhb line); 995154941Sjhb } 996154941Sjhb} 997154941Sjhb#endif /* INVARIANT_SUPPORT */ 998154941Sjhb 999154941Sjhb#ifdef DDB 1000154941Sjhbvoid 1001154941Sjhbdb_show_rwlock(struct lock_object *lock) 1002154941Sjhb{ 1003154941Sjhb struct rwlock *rw; 1004154941Sjhb struct thread *td; 1005154941Sjhb 1006154941Sjhb rw = (struct rwlock *)lock; 1007154941Sjhb 1008154941Sjhb db_printf(" state: "); 1009154941Sjhb if (rw->rw_lock == RW_UNLOCKED) 1010154941Sjhb db_printf("UNLOCKED\n"); 1011169394Sjhb else if (rw->rw_lock == RW_DESTROYED) { 1012169394Sjhb db_printf("DESTROYED\n"); 1013169394Sjhb return; 1014169394Sjhb } else if (rw->rw_lock & RW_LOCK_READ) 1015167504Sjhb db_printf("RLOCK: %ju locks\n", 1016167504Sjhb (uintmax_t)(RW_READERS(rw->rw_lock))); 1017154941Sjhb else { 1018157826Sjhb td = rw_wowner(rw); 1019154941Sjhb db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1020173600Sjulian td->td_tid, td->td_proc->p_pid, td->td_name); 1021171052Sattilio if (rw_recursed(rw)) 1022171052Sattilio db_printf(" recursed: %u\n", rw->rw_recurse); 1023154941Sjhb } 1024154941Sjhb db_printf(" waiters: "); 1025154941Sjhb switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { 1026154941Sjhb case RW_LOCK_READ_WAITERS: 1027154941Sjhb db_printf("readers\n"); 1028154941Sjhb break; 1029154941Sjhb case RW_LOCK_WRITE_WAITERS: 1030154941Sjhb db_printf("writers\n"); 1031154941Sjhb break; 1032154941Sjhb case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: 1033167492Sjhb db_printf("readers and writers\n"); 1034154941Sjhb break; 1035154941Sjhb default: 1036154941Sjhb db_printf("none\n"); 1037154941Sjhb break; 1038154941Sjhb } 1039154941Sjhb} 1040154941Sjhb 1041154941Sjhb#endif 1042