kern_rwlock.c revision 182914
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 182914 2008-09-10 19:13:30Z jhb $"); 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 194167024Srwatsonint 195167024Srwatsonrw_wowned(struct rwlock *rw) 196167024Srwatson{ 197167024Srwatson 198167024Srwatson return (rw_wowner(rw) == curthread); 199167024Srwatson} 200167024Srwatson 201154941Sjhbvoid 202154941Sjhb_rw_wlock(struct rwlock *rw, const char *file, int line) 203154941Sjhb{ 204154941Sjhb 205154941Sjhb MPASS(curthread != NULL); 206169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 207169394Sjhb ("rw_wlock() of destroyed rwlock @ %s:%d", file, line)); 208167787Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file, 209182914Sjhb line, NULL); 210154941Sjhb __rw_wlock(rw, curthread, file, line); 211171052Sattilio LOCK_LOG_LOCK("WLOCK", &rw->lock_object, 0, rw->rw_recurse, file, line); 212167787Sjhb WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 213160771Sjhb curthread->td_locks++; 214154941Sjhb} 215154941Sjhb 216177843Sattilioint 217177843Sattilio_rw_try_wlock(struct rwlock *rw, const char *file, int line) 218177843Sattilio{ 219177843Sattilio int rval; 220177843Sattilio 221177843Sattilio KASSERT(rw->rw_lock != RW_DESTROYED, 222177843Sattilio ("rw_try_wlock() of destroyed rwlock @ %s:%d", file, line)); 223177843Sattilio 224177843Sattilio if (rw_wlocked(rw) && (rw->lock_object.lo_flags & RW_RECURSE) != 0) { 225177843Sattilio rw->rw_recurse++; 226177843Sattilio rval = 1; 227177843Sattilio } else 228177843Sattilio rval = atomic_cmpset_acq_ptr(&rw->rw_lock, RW_UNLOCKED, 229177843Sattilio (uintptr_t)curthread); 230177843Sattilio 231177843Sattilio LOCK_LOG_TRY("WLOCK", &rw->lock_object, 0, rval, file, line); 232177843Sattilio if (rval) { 233177843Sattilio WITNESS_LOCK(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 234177843Sattilio file, line); 235177843Sattilio curthread->td_locks++; 236177843Sattilio } 237177843Sattilio return (rval); 238177843Sattilio} 239177843Sattilio 240154941Sjhbvoid 241154941Sjhb_rw_wunlock(struct rwlock *rw, const char *file, int line) 242154941Sjhb{ 243154941Sjhb 244154941Sjhb MPASS(curthread != NULL); 245169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 246169394Sjhb ("rw_wunlock() of destroyed rwlock @ %s:%d", file, line)); 247154941Sjhb _rw_assert(rw, RA_WLOCKED, file, line); 248160771Sjhb curthread->td_locks--; 249167787Sjhb WITNESS_UNLOCK(&rw->lock_object, LOP_EXCLUSIVE, file, line); 250171052Sattilio LOCK_LOG_LOCK("WUNLOCK", &rw->lock_object, 0, rw->rw_recurse, file, 251171052Sattilio line); 252171052Sattilio if (!rw_recursed(rw)) 253171052Sattilio lock_profile_release_lock(&rw->lock_object); 254154941Sjhb __rw_wunlock(rw, curthread, file, line); 255154941Sjhb} 256176017Sjeff/* 257176017Sjeff * Determines whether a new reader can acquire a lock. Succeeds if the 258176017Sjeff * reader already owns a read lock and the lock is locked for read to 259176017Sjeff * prevent deadlock from reader recursion. Also succeeds if the lock 260176017Sjeff * is unlocked and has no writer waiters or spinners. Failing otherwise 261176017Sjeff * prioritizes writers before readers. 262176017Sjeff */ 263176017Sjeff#define RW_CAN_READ(_rw) \ 264176017Sjeff ((curthread->td_rw_rlocks && (_rw) & RW_LOCK_READ) || ((_rw) & \ 265176017Sjeff (RW_LOCK_READ | RW_LOCK_WRITE_WAITERS | RW_LOCK_WRITE_SPINNER)) == \ 266176017Sjeff RW_LOCK_READ) 267154941Sjhb 268154941Sjhbvoid 269154941Sjhb_rw_rlock(struct rwlock *rw, const char *file, int line) 270154941Sjhb{ 271170295Sjeff struct turnstile *ts; 272167801Sjhb#ifdef ADAPTIVE_RWLOCKS 273157846Sjhb volatile struct thread *owner; 274177912Sjeff int spintries = 0; 275177912Sjeff int i; 276157851Swkoszek#endif 277167307Sjhb uint64_t waittime = 0; 278167054Skmacy int contested = 0; 279176017Sjeff uintptr_t v; 280154941Sjhb 281169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 282169394Sjhb ("rw_rlock() of destroyed rwlock @ %s:%d", file, line)); 283157826Sjhb KASSERT(rw_wowner(rw) != curthread, 284154941Sjhb ("%s (%s): wlock already held @ %s:%d", __func__, 285167787Sjhb rw->lock_object.lo_name, file, line)); 286182914Sjhb WITNESS_CHECKORDER(&rw->lock_object, LOP_NEWORDER, file, line, NULL); 287154941Sjhb 288154941Sjhb for (;;) { 289154941Sjhb /* 290154941Sjhb * Handle the easy case. If no other thread has a write 291154941Sjhb * lock, then try to bump up the count of read locks. Note 292154941Sjhb * that we have to preserve the current state of the 293154941Sjhb * RW_LOCK_WRITE_WAITERS flag. If we fail to acquire a 294154941Sjhb * read lock, then rw_lock must have changed, so restart 295154941Sjhb * the loop. Note that this handles the case of a 296154941Sjhb * completely unlocked rwlock since such a lock is encoded 297154941Sjhb * as a read lock with no waiters. 298154941Sjhb */ 299176017Sjeff v = rw->rw_lock; 300176017Sjeff if (RW_CAN_READ(v)) { 301154941Sjhb /* 302154941Sjhb * The RW_LOCK_READ_WAITERS flag should only be set 303176017Sjeff * if the lock has been unlocked and write waiters 304176017Sjeff * were present. 305154941Sjhb */ 306176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, 307176017Sjeff v + RW_ONE_READER)) { 308167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 309154941Sjhb CTR4(KTR_LOCK, 310154941Sjhb "%s: %p succeed %p -> %p", __func__, 311176017Sjeff rw, (void *)v, 312176017Sjeff (void *)(v + RW_ONE_READER)); 313154941Sjhb break; 314154941Sjhb } 315157846Sjhb cpu_spinwait(); 316154941Sjhb continue; 317154941Sjhb } 318174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 319174629Sjeff &contested, &waittime); 320154941Sjhb 321173960Sattilio#ifdef ADAPTIVE_RWLOCKS 322154941Sjhb /* 323173960Sattilio * If the owner is running on another CPU, spin until 324173960Sattilio * the owner stops running or the state of the lock 325173960Sattilio * changes. 326173960Sattilio */ 327176017Sjeff if ((v & RW_LOCK_READ) == 0) { 328176017Sjeff owner = (struct thread *)RW_OWNER(v); 329176017Sjeff if (TD_IS_RUNNING(owner)) { 330176017Sjeff if (LOCK_LOG_TEST(&rw->lock_object, 0)) 331176017Sjeff CTR3(KTR_LOCK, 332176017Sjeff "%s: spinning on %p held by %p", 333176017Sjeff __func__, rw, owner); 334176017Sjeff while ((struct thread*)RW_OWNER(rw->rw_lock) == 335176017Sjeff owner && TD_IS_RUNNING(owner)) 336176017Sjeff cpu_spinwait(); 337176017Sjeff continue; 338176017Sjeff } 339177912Sjeff } else if (spintries < rowner_retries) { 340177912Sjeff spintries++; 341177912Sjeff for (i = 0; i < rowner_loops; i++) { 342177912Sjeff v = rw->rw_lock; 343177912Sjeff if ((v & RW_LOCK_READ) == 0 || RW_CAN_READ(v)) 344177912Sjeff break; 345177912Sjeff cpu_spinwait(); 346177912Sjeff } 347177912Sjeff if (i != rowner_loops) 348177912Sjeff continue; 349173960Sattilio } 350173960Sattilio#endif 351173960Sattilio 352173960Sattilio /* 353154941Sjhb * Okay, now it's the hard case. Some other thread already 354176017Sjeff * has a write lock or there are write waiters present, 355176017Sjeff * acquire the turnstile lock so we can begin the process 356176017Sjeff * of blocking. 357154941Sjhb */ 358170295Sjeff ts = turnstile_trywait(&rw->lock_object); 359154941Sjhb 360154941Sjhb /* 361154941Sjhb * The lock might have been released while we spun, so 362176017Sjeff * recheck its state and restart the loop if needed. 363154941Sjhb */ 364176017Sjeff v = rw->rw_lock; 365176017Sjeff if (RW_CAN_READ(v)) { 366170295Sjeff turnstile_cancel(ts); 367157846Sjhb cpu_spinwait(); 368154941Sjhb continue; 369154941Sjhb } 370154941Sjhb 371173960Sattilio#ifdef ADAPTIVE_RWLOCKS 372154941Sjhb /* 373173960Sattilio * If the current owner of the lock is executing on another 374173960Sattilio * CPU quit the hard path and try to spin. 375173960Sattilio */ 376176017Sjeff if ((v & RW_LOCK_READ) == 0) { 377176017Sjeff owner = (struct thread *)RW_OWNER(v); 378176017Sjeff if (TD_IS_RUNNING(owner)) { 379176017Sjeff turnstile_cancel(ts); 380176017Sjeff cpu_spinwait(); 381176017Sjeff continue; 382176017Sjeff } 383173960Sattilio } 384173960Sattilio#endif 385173960Sattilio 386173960Sattilio /* 387176017Sjeff * The lock is held in write mode or it already has waiters. 388154941Sjhb */ 389176017Sjeff MPASS(!RW_CAN_READ(v)); 390176017Sjeff 391176017Sjeff /* 392176017Sjeff * If the RW_LOCK_READ_WAITERS flag is already set, then 393176017Sjeff * we can go ahead and block. If it is not set then try 394176017Sjeff * to set it. If we fail to set it drop the turnstile 395176017Sjeff * lock and restart the loop. 396176017Sjeff */ 397176017Sjeff if (!(v & RW_LOCK_READ_WAITERS)) { 398176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 399176017Sjeff v | RW_LOCK_READ_WAITERS)) { 400170295Sjeff turnstile_cancel(ts); 401157826Sjhb cpu_spinwait(); 402157826Sjhb continue; 403157826Sjhb } 404167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 405157826Sjhb CTR2(KTR_LOCK, "%s: %p set read waiters flag", 406157826Sjhb __func__, rw); 407154941Sjhb } 408154941Sjhb 409154941Sjhb /* 410154941Sjhb * We were unable to acquire the lock and the read waiters 411154941Sjhb * flag is set, so we must block on the turnstile. 412154941Sjhb */ 413167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 414154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 415154941Sjhb rw); 416170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_SHARED_QUEUE); 417167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 418154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 419154941Sjhb __func__, rw); 420154941Sjhb } 421154941Sjhb 422154941Sjhb /* 423154941Sjhb * TODO: acquire "owner of record" here. Here be turnstile dragons 424154941Sjhb * however. turnstiles don't like owners changing between calls to 425154941Sjhb * turnstile_wait() currently. 426154941Sjhb */ 427174629Sjeff lock_profile_obtain_lock_success( &rw->lock_object, contested, 428174629Sjeff waittime, file, line); 429167787Sjhb LOCK_LOG_LOCK("RLOCK", &rw->lock_object, 0, 0, file, line); 430167787Sjhb WITNESS_LOCK(&rw->lock_object, 0, file, line); 431160771Sjhb curthread->td_locks++; 432176017Sjeff curthread->td_rw_rlocks++; 433154941Sjhb} 434154941Sjhb 435177843Sattilioint 436177843Sattilio_rw_try_rlock(struct rwlock *rw, const char *file, int line) 437177843Sattilio{ 438177843Sattilio uintptr_t x; 439177843Sattilio 440177843Sattilio for (;;) { 441177843Sattilio x = rw->rw_lock; 442177843Sattilio KASSERT(rw->rw_lock != RW_DESTROYED, 443177843Sattilio ("rw_try_rlock() of destroyed rwlock @ %s:%d", file, line)); 444177843Sattilio if (!(x & RW_LOCK_READ)) 445177843Sattilio break; 446177843Sattilio if (atomic_cmpset_acq_ptr(&rw->rw_lock, x, x + RW_ONE_READER)) { 447177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 1, file, 448177843Sattilio line); 449177843Sattilio WITNESS_LOCK(&rw->lock_object, LOP_TRYLOCK, file, line); 450177843Sattilio curthread->td_locks++; 451177843Sattilio curthread->td_rw_rlocks++; 452177843Sattilio return (1); 453177843Sattilio } 454177843Sattilio } 455177843Sattilio 456177843Sattilio LOCK_LOG_TRY("RLOCK", &rw->lock_object, 0, 0, file, line); 457177843Sattilio return (0); 458177843Sattilio} 459177843Sattilio 460154941Sjhbvoid 461154941Sjhb_rw_runlock(struct rwlock *rw, const char *file, int line) 462154941Sjhb{ 463154941Sjhb struct turnstile *ts; 464176017Sjeff uintptr_t x, v, queue; 465154941Sjhb 466169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 467169394Sjhb ("rw_runlock() of destroyed rwlock @ %s:%d", file, line)); 468154941Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 469160771Sjhb curthread->td_locks--; 470176017Sjeff curthread->td_rw_rlocks--; 471167787Sjhb WITNESS_UNLOCK(&rw->lock_object, 0, file, line); 472167787Sjhb LOCK_LOG_LOCK("RUNLOCK", &rw->lock_object, 0, 0, file, line); 473154941Sjhb 474154941Sjhb /* TODO: drop "owner of record" here. */ 475154941Sjhb 476154941Sjhb for (;;) { 477154941Sjhb /* 478154941Sjhb * See if there is more than one read lock held. If so, 479154941Sjhb * just drop one and return. 480154941Sjhb */ 481154941Sjhb x = rw->rw_lock; 482154941Sjhb if (RW_READERS(x) > 1) { 483154941Sjhb if (atomic_cmpset_ptr(&rw->rw_lock, x, 484154941Sjhb x - RW_ONE_READER)) { 485167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 486154941Sjhb CTR4(KTR_LOCK, 487154941Sjhb "%s: %p succeeded %p -> %p", 488154941Sjhb __func__, rw, (void *)x, 489154941Sjhb (void *)(x - RW_ONE_READER)); 490154941Sjhb break; 491154941Sjhb } 492154941Sjhb continue; 493167307Sjhb } 494154941Sjhb /* 495154941Sjhb * If there aren't any waiters for a write lock, then try 496154941Sjhb * to drop it quickly. 497154941Sjhb */ 498176017Sjeff if (!(x & RW_LOCK_WAITERS)) { 499176017Sjeff MPASS((x & ~RW_LOCK_WRITE_SPINNER) == 500176017Sjeff RW_READERS_LOCK(1)); 501176017Sjeff if (atomic_cmpset_ptr(&rw->rw_lock, x, RW_UNLOCKED)) { 502167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 503154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded", 504154941Sjhb __func__, rw); 505154941Sjhb break; 506154941Sjhb } 507154941Sjhb continue; 508154941Sjhb } 509154941Sjhb /* 510176017Sjeff * Ok, we know we have waiters and we think we are the 511176017Sjeff * last reader, so grab the turnstile lock. 512154941Sjhb */ 513170295Sjeff turnstile_chain_lock(&rw->lock_object); 514176017Sjeff v = rw->rw_lock & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 515176017Sjeff MPASS(v & RW_LOCK_WAITERS); 516154941Sjhb 517154941Sjhb /* 518154941Sjhb * Try to drop our lock leaving the lock in a unlocked 519154941Sjhb * state. 520154941Sjhb * 521154941Sjhb * If you wanted to do explicit lock handoff you'd have to 522154941Sjhb * do it here. You'd also want to use turnstile_signal() 523154941Sjhb * and you'd have to handle the race where a higher 524154941Sjhb * priority thread blocks on the write lock before the 525154941Sjhb * thread you wakeup actually runs and have the new thread 526154941Sjhb * "steal" the lock. For now it's a lot simpler to just 527154941Sjhb * wakeup all of the waiters. 528154941Sjhb * 529154941Sjhb * As above, if we fail, then another thread might have 530154941Sjhb * acquired a read lock, so drop the turnstile lock and 531154941Sjhb * restart. 532154941Sjhb */ 533176017Sjeff x = RW_UNLOCKED; 534176017Sjeff if (v & RW_LOCK_WRITE_WAITERS) { 535176017Sjeff queue = TS_EXCLUSIVE_QUEUE; 536176017Sjeff x |= (v & RW_LOCK_READ_WAITERS); 537176017Sjeff } else 538176017Sjeff queue = TS_SHARED_QUEUE; 539176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v, 540176017Sjeff x)) { 541170295Sjeff turnstile_chain_unlock(&rw->lock_object); 542154941Sjhb continue; 543154941Sjhb } 544167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 545154941Sjhb CTR2(KTR_LOCK, "%s: %p last succeeded with waiters", 546154941Sjhb __func__, rw); 547154941Sjhb 548154941Sjhb /* 549154941Sjhb * Ok. The lock is released and all that's left is to 550154941Sjhb * wake up the waiters. Note that the lock might not be 551154941Sjhb * free anymore, but in that case the writers will just 552154941Sjhb * block again if they run before the new lock holder(s) 553154941Sjhb * release the lock. 554154941Sjhb */ 555167787Sjhb ts = turnstile_lookup(&rw->lock_object); 556157846Sjhb MPASS(ts != NULL); 557176017Sjeff turnstile_broadcast(ts, queue); 558154941Sjhb turnstile_unpend(ts, TS_SHARED_LOCK); 559170295Sjeff turnstile_chain_unlock(&rw->lock_object); 560154941Sjhb break; 561154941Sjhb } 562174629Sjeff lock_profile_release_lock(&rw->lock_object); 563154941Sjhb} 564154941Sjhb 565154941Sjhb/* 566154941Sjhb * This function is called when we are unable to obtain a write lock on the 567154941Sjhb * first try. This means that at least one other thread holds either a 568154941Sjhb * read or write lock. 569154941Sjhb */ 570154941Sjhbvoid 571154941Sjhb_rw_wlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 572154941Sjhb{ 573170295Sjeff struct turnstile *ts; 574167801Sjhb#ifdef ADAPTIVE_RWLOCKS 575157846Sjhb volatile struct thread *owner; 576176017Sjeff int spintries = 0; 577176017Sjeff int i; 578157851Swkoszek#endif 579171516Sattilio uint64_t waittime = 0; 580176017Sjeff uintptr_t v, x; 581171516Sattilio int contested = 0; 582154941Sjhb 583171052Sattilio if (rw_wlocked(rw)) { 584171052Sattilio KASSERT(rw->lock_object.lo_flags & RW_RECURSE, 585171052Sattilio ("%s: recursing but non-recursive rw %s @ %s:%d\n", 586171052Sattilio __func__, rw->lock_object.lo_name, file, line)); 587171052Sattilio rw->rw_recurse++; 588171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 589171052Sattilio CTR2(KTR_LOCK, "%s: %p recursing", __func__, rw); 590171052Sattilio return; 591171052Sattilio } 592171052Sattilio 593167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 594154941Sjhb CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__, 595167787Sjhb rw->lock_object.lo_name, (void *)rw->rw_lock, file, line); 596154941Sjhb 597154941Sjhb while (!_rw_write_lock(rw, tid)) { 598174629Sjeff lock_profile_obtain_lock_failed(&rw->lock_object, 599174629Sjeff &contested, &waittime); 600173960Sattilio#ifdef ADAPTIVE_RWLOCKS 601173960Sattilio /* 602173960Sattilio * If the lock is write locked and the owner is 603173960Sattilio * running on another CPU, spin until the owner stops 604173960Sattilio * running or the state of the lock changes. 605173960Sattilio */ 606173960Sattilio v = rw->rw_lock; 607173960Sattilio owner = (struct thread *)RW_OWNER(v); 608173960Sattilio if (!(v & RW_LOCK_READ) && TD_IS_RUNNING(owner)) { 609173960Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 610173960Sattilio CTR3(KTR_LOCK, "%s: spinning on %p held by %p", 611173960Sattilio __func__, rw, owner); 612173960Sattilio while ((struct thread*)RW_OWNER(rw->rw_lock) == owner && 613173960Sattilio TD_IS_RUNNING(owner)) 614173960Sattilio cpu_spinwait(); 615173960Sattilio continue; 616173960Sattilio } 617177912Sjeff if ((v & RW_LOCK_READ) && RW_READERS(v) && 618177912Sjeff spintries < rowner_retries) { 619176017Sjeff if (!(v & RW_LOCK_WRITE_SPINNER)) { 620176017Sjeff if (!atomic_cmpset_ptr(&rw->rw_lock, v, 621176017Sjeff v | RW_LOCK_WRITE_SPINNER)) { 622176017Sjeff cpu_spinwait(); 623176017Sjeff continue; 624176017Sjeff } 625176017Sjeff } 626176017Sjeff spintries++; 627177912Sjeff for (i = 0; i < rowner_loops; i++) { 628176017Sjeff if ((rw->rw_lock & RW_LOCK_WRITE_SPINNER) == 0) 629176017Sjeff break; 630176017Sjeff cpu_spinwait(); 631176017Sjeff } 632177912Sjeff if (i != rowner_loops) 633176017Sjeff continue; 634176017Sjeff } 635173960Sattilio#endif 636170295Sjeff ts = turnstile_trywait(&rw->lock_object); 637154941Sjhb v = rw->rw_lock; 638154941Sjhb 639173960Sattilio#ifdef ADAPTIVE_RWLOCKS 640154941Sjhb /* 641173960Sattilio * If the current owner of the lock is executing on another 642173960Sattilio * CPU quit the hard path and try to spin. 643173960Sattilio */ 644173960Sattilio if (!(v & RW_LOCK_READ)) { 645173960Sattilio owner = (struct thread *)RW_OWNER(v); 646173960Sattilio if (TD_IS_RUNNING(owner)) { 647173960Sattilio turnstile_cancel(ts); 648173960Sattilio cpu_spinwait(); 649173960Sattilio continue; 650173960Sattilio } 651173960Sattilio } 652173960Sattilio#endif 653173960Sattilio /* 654179334Sattilio * Check for the waiters flags about this rwlock. 655179334Sattilio * If the lock was released, without maintain any pending 656179334Sattilio * waiters queue, simply try to acquire it. 657179334Sattilio * If a pending waiters queue is present, claim the lock 658179334Sattilio * ownership and maintain the pending queue. 659154941Sjhb */ 660176017Sjeff x = v & (RW_LOCK_WAITERS | RW_LOCK_WRITE_SPINNER); 661176017Sjeff if ((v & ~x) == RW_UNLOCKED) { 662176017Sjeff x &= ~RW_LOCK_WRITE_SPINNER; 663176017Sjeff if (atomic_cmpset_acq_ptr(&rw->rw_lock, v, tid | x)) { 664176017Sjeff if (x) 665176017Sjeff turnstile_claim(ts); 666176017Sjeff else 667176017Sjeff turnstile_cancel(ts); 668154941Sjhb break; 669154941Sjhb } 670170295Sjeff turnstile_cancel(ts); 671154941Sjhb cpu_spinwait(); 672154941Sjhb continue; 673154941Sjhb } 674154941Sjhb /* 675154941Sjhb * If the RW_LOCK_WRITE_WAITERS flag isn't set, then try to 676154941Sjhb * set it. If we fail to set it, then loop back and try 677154941Sjhb * again. 678154941Sjhb */ 679157826Sjhb if (!(v & RW_LOCK_WRITE_WAITERS)) { 680157826Sjhb if (!atomic_cmpset_ptr(&rw->rw_lock, v, 681157826Sjhb v | RW_LOCK_WRITE_WAITERS)) { 682170295Sjeff turnstile_cancel(ts); 683157826Sjhb cpu_spinwait(); 684157826Sjhb continue; 685157826Sjhb } 686167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 687157826Sjhb CTR2(KTR_LOCK, "%s: %p set write waiters flag", 688157826Sjhb __func__, rw); 689154941Sjhb } 690157846Sjhb /* 691154941Sjhb * We were unable to acquire the lock and the write waiters 692154941Sjhb * flag is set, so we must block on the turnstile. 693154941Sjhb */ 694167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 695154941Sjhb CTR2(KTR_LOCK, "%s: %p blocking on turnstile", __func__, 696154941Sjhb rw); 697170295Sjeff turnstile_wait(ts, rw_owner(rw), TS_EXCLUSIVE_QUEUE); 698167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 699154941Sjhb CTR2(KTR_LOCK, "%s: %p resuming from turnstile", 700154941Sjhb __func__, rw); 701176017Sjeff#ifdef ADAPTIVE_RWLOCKS 702176017Sjeff spintries = 0; 703176017Sjeff#endif 704154941Sjhb } 705171516Sattilio lock_profile_obtain_lock_success(&rw->lock_object, contested, waittime, 706171516Sattilio file, line); 707154941Sjhb} 708154941Sjhb 709154941Sjhb/* 710154941Sjhb * This function is called if the first try at releasing a write lock failed. 711154941Sjhb * This means that one of the 2 waiter bits must be set indicating that at 712154941Sjhb * least one thread is waiting on this lock. 713154941Sjhb */ 714154941Sjhbvoid 715154941Sjhb_rw_wunlock_hard(struct rwlock *rw, uintptr_t tid, const char *file, int line) 716154941Sjhb{ 717154941Sjhb struct turnstile *ts; 718154941Sjhb uintptr_t v; 719154941Sjhb int queue; 720154941Sjhb 721171052Sattilio if (rw_wlocked(rw) && rw_recursed(rw)) { 722176017Sjeff rw->rw_recurse--; 723171052Sattilio if (LOCK_LOG_TEST(&rw->lock_object, 0)) 724171052Sattilio CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, rw); 725171052Sattilio return; 726171052Sattilio } 727176017Sjeff v = rw->rw_lock; 728171052Sattilio 729154941Sjhb KASSERT(rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS), 730154941Sjhb ("%s: neither of the waiter flags are set", __func__)); 731154941Sjhb 732167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 733154941Sjhb CTR2(KTR_LOCK, "%s: %p contested", __func__, rw); 734154941Sjhb 735170295Sjeff turnstile_chain_lock(&rw->lock_object); 736167787Sjhb ts = turnstile_lookup(&rw->lock_object); 737154941Sjhb MPASS(ts != NULL); 738154941Sjhb 739154941Sjhb /* 740154941Sjhb * Use the same algo as sx locks for now. Prefer waking up shared 741154941Sjhb * waiters if we have any over writers. This is probably not ideal. 742154941Sjhb * 743154941Sjhb * 'v' is the value we are going to write back to rw_lock. If we 744154941Sjhb * have waiters on both queues, we need to preserve the state of 745154941Sjhb * the waiter flag for the queue we don't wake up. For now this is 746154941Sjhb * hardcoded for the algorithm mentioned above. 747154941Sjhb * 748154941Sjhb * In the case of both readers and writers waiting we wakeup the 749154941Sjhb * readers but leave the RW_LOCK_WRITE_WAITERS flag set. If a 750154941Sjhb * new writer comes in before a reader it will claim the lock up 751154941Sjhb * above. There is probably a potential priority inversion in 752154941Sjhb * there that could be worked around either by waking both queues 753154941Sjhb * of waiters or doing some complicated lock handoff gymnastics. 754154941Sjhb */ 755157846Sjhb v = RW_UNLOCKED; 756176076Sjeff if (rw->rw_lock & RW_LOCK_WRITE_WAITERS) { 757176076Sjeff queue = TS_EXCLUSIVE_QUEUE; 758176076Sjeff v |= (rw->rw_lock & RW_LOCK_READ_WAITERS); 759176076Sjeff } else 760154941Sjhb queue = TS_SHARED_QUEUE; 761157846Sjhb 762157846Sjhb /* Wake up all waiters for the specific queue. */ 763167787Sjhb if (LOCK_LOG_TEST(&rw->lock_object, 0)) 764154941Sjhb CTR3(KTR_LOCK, "%s: %p waking up %s waiters", __func__, rw, 765154941Sjhb queue == TS_SHARED_QUEUE ? "read" : "write"); 766154941Sjhb turnstile_broadcast(ts, queue); 767154941Sjhb atomic_store_rel_ptr(&rw->rw_lock, v); 768154941Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 769170295Sjeff turnstile_chain_unlock(&rw->lock_object); 770154941Sjhb} 771154941Sjhb 772157882Sjhb/* 773157882Sjhb * Attempt to do a non-blocking upgrade from a read lock to a write 774157882Sjhb * lock. This will only succeed if this thread holds a single read 775157882Sjhb * lock. Returns true if the upgrade succeeded and false otherwise. 776157882Sjhb */ 777157882Sjhbint 778157882Sjhb_rw_try_upgrade(struct rwlock *rw, const char *file, int line) 779157882Sjhb{ 780176017Sjeff uintptr_t v, x, tid; 781170295Sjeff struct turnstile *ts; 782157882Sjhb int success; 783157882Sjhb 784169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 785169394Sjhb ("rw_try_upgrade() of destroyed rwlock @ %s:%d", file, line)); 786157882Sjhb _rw_assert(rw, RA_RLOCKED, file, line); 787157882Sjhb 788157882Sjhb /* 789157882Sjhb * Attempt to switch from one reader to a writer. If there 790157882Sjhb * are any write waiters, then we will have to lock the 791157882Sjhb * turnstile first to prevent races with another writer 792157882Sjhb * calling turnstile_wait() before we have claimed this 793157882Sjhb * turnstile. So, do the simple case of no waiters first. 794157882Sjhb */ 795157882Sjhb tid = (uintptr_t)curthread; 796176017Sjeff success = 0; 797176017Sjeff for (;;) { 798176017Sjeff v = rw->rw_lock; 799176017Sjeff if (RW_READERS(v) > 1) 800176017Sjeff break; 801176017Sjeff if (!(v & RW_LOCK_WAITERS)) { 802176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid); 803176017Sjeff if (!success) 804176017Sjeff continue; 805176017Sjeff break; 806176017Sjeff } 807157882Sjhb 808176017Sjeff /* 809176017Sjeff * Ok, we think we have waiters, so lock the turnstile. 810176017Sjeff */ 811176017Sjeff ts = turnstile_trywait(&rw->lock_object); 812176017Sjeff v = rw->rw_lock; 813176017Sjeff if (RW_READERS(v) > 1) { 814176017Sjeff turnstile_cancel(ts); 815176017Sjeff break; 816176017Sjeff } 817176017Sjeff /* 818176017Sjeff * Try to switch from one reader to a writer again. This time 819176017Sjeff * we honor the current state of the waiters flags. 820176017Sjeff * If we obtain the lock with the flags set, then claim 821176017Sjeff * ownership of the turnstile. 822176017Sjeff */ 823176017Sjeff x = rw->rw_lock & RW_LOCK_WAITERS; 824176017Sjeff success = atomic_cmpset_ptr(&rw->rw_lock, v, tid | x); 825176017Sjeff if (success) { 826176017Sjeff if (x) 827176017Sjeff turnstile_claim(ts); 828176017Sjeff else 829176017Sjeff turnstile_cancel(ts); 830176017Sjeff break; 831176017Sjeff } 832170295Sjeff turnstile_cancel(ts); 833176017Sjeff } 834167787Sjhb LOCK_LOG_TRY("WUPGRADE", &rw->lock_object, 0, success, file, line); 835176017Sjeff if (success) { 836176017Sjeff curthread->td_rw_rlocks--; 837167787Sjhb WITNESS_UPGRADE(&rw->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK, 838157882Sjhb file, line); 839176017Sjeff } 840157882Sjhb return (success); 841157882Sjhb} 842157882Sjhb 843157882Sjhb/* 844157882Sjhb * Downgrade a write lock into a single read lock. 845157882Sjhb */ 846157882Sjhbvoid 847157882Sjhb_rw_downgrade(struct rwlock *rw, const char *file, int line) 848157882Sjhb{ 849157882Sjhb struct turnstile *ts; 850157882Sjhb uintptr_t tid, v; 851176017Sjeff int rwait, wwait; 852157882Sjhb 853169394Sjhb KASSERT(rw->rw_lock != RW_DESTROYED, 854169394Sjhb ("rw_downgrade() of destroyed rwlock @ %s:%d", file, line)); 855171052Sattilio _rw_assert(rw, RA_WLOCKED | RA_NOTRECURSED, file, line); 856171052Sattilio#ifndef INVARIANTS 857171052Sattilio if (rw_recursed(rw)) 858171052Sattilio panic("downgrade of a recursed lock"); 859171052Sattilio#endif 860157882Sjhb 861167787Sjhb WITNESS_DOWNGRADE(&rw->lock_object, 0, file, line); 862157882Sjhb 863157882Sjhb /* 864157882Sjhb * Convert from a writer to a single reader. First we handle 865157882Sjhb * the easy case with no waiters. If there are any waiters, we 866176017Sjeff * lock the turnstile and "disown" the lock. 867157882Sjhb */ 868157882Sjhb tid = (uintptr_t)curthread; 869157882Sjhb if (atomic_cmpset_rel_ptr(&rw->rw_lock, tid, RW_READERS_LOCK(1))) 870157882Sjhb goto out; 871157882Sjhb 872157882Sjhb /* 873157882Sjhb * Ok, we think we have waiters, so lock the turnstile so we can 874157882Sjhb * read the waiter flags without any races. 875157882Sjhb */ 876170295Sjeff turnstile_chain_lock(&rw->lock_object); 877176017Sjeff v = rw->rw_lock & RW_LOCK_WAITERS; 878176017Sjeff rwait = v & RW_LOCK_READ_WAITERS; 879176017Sjeff wwait = v & RW_LOCK_WRITE_WAITERS; 880176017Sjeff MPASS(rwait | wwait); 881157882Sjhb 882157882Sjhb /* 883176017Sjeff * Downgrade from a write lock while preserving waiters flag 884176017Sjeff * and give up ownership of the turnstile. 885157882Sjhb */ 886167787Sjhb ts = turnstile_lookup(&rw->lock_object); 887157882Sjhb MPASS(ts != NULL); 888176017Sjeff if (!wwait) 889176017Sjeff v &= ~RW_LOCK_READ_WAITERS; 890176017Sjeff atomic_store_rel_ptr(&rw->rw_lock, RW_READERS_LOCK(1) | v); 891176017Sjeff /* 892176017Sjeff * Wake other readers if there are no writers pending. Otherwise they 893176017Sjeff * won't be able to acquire the lock anyway. 894176017Sjeff */ 895176017Sjeff if (rwait && !wwait) { 896157882Sjhb turnstile_broadcast(ts, TS_SHARED_QUEUE); 897157882Sjhb turnstile_unpend(ts, TS_EXCLUSIVE_LOCK); 898176017Sjeff } else 899157882Sjhb turnstile_disown(ts); 900170295Sjeff turnstile_chain_unlock(&rw->lock_object); 901157882Sjhbout: 902176017Sjeff curthread->td_rw_rlocks++; 903167787Sjhb LOCK_LOG_LOCK("WDOWNGRADE", &rw->lock_object, 0, 0, file, line); 904157882Sjhb} 905157882Sjhb 906154941Sjhb#ifdef INVARIANT_SUPPORT 907155162Sscottl#ifndef INVARIANTS 908154941Sjhb#undef _rw_assert 909154941Sjhb#endif 910154941Sjhb 911154941Sjhb/* 912154941Sjhb * In the non-WITNESS case, rw_assert() can only detect that at least 913154941Sjhb * *some* thread owns an rlock, but it cannot guarantee that *this* 914154941Sjhb * thread owns an rlock. 915154941Sjhb */ 916154941Sjhbvoid 917154941Sjhb_rw_assert(struct rwlock *rw, int what, const char *file, int line) 918154941Sjhb{ 919154941Sjhb 920154941Sjhb if (panicstr != NULL) 921154941Sjhb return; 922154941Sjhb switch (what) { 923154941Sjhb case RA_LOCKED: 924171052Sattilio case RA_LOCKED | RA_RECURSED: 925171052Sattilio case RA_LOCKED | RA_NOTRECURSED: 926154941Sjhb case RA_RLOCKED: 927154941Sjhb#ifdef WITNESS 928167787Sjhb witness_assert(&rw->lock_object, what, file, line); 929154941Sjhb#else 930154941Sjhb /* 931154941Sjhb * If some other thread has a write lock or we have one 932154941Sjhb * and are asserting a read lock, fail. Also, if no one 933154941Sjhb * has a lock at all, fail. 934154941Sjhb */ 935155061Sscottl if (rw->rw_lock == RW_UNLOCKED || 936155061Sscottl (!(rw->rw_lock & RW_LOCK_READ) && (what == RA_RLOCKED || 937157826Sjhb rw_wowner(rw) != curthread))) 938154941Sjhb panic("Lock %s not %slocked @ %s:%d\n", 939167787Sjhb rw->lock_object.lo_name, (what == RA_RLOCKED) ? 940154941Sjhb "read " : "", file, line); 941171052Sattilio 942171052Sattilio if (!(rw->rw_lock & RW_LOCK_READ)) { 943171052Sattilio if (rw_recursed(rw)) { 944171052Sattilio if (what & RA_NOTRECURSED) 945171052Sattilio panic("Lock %s recursed @ %s:%d\n", 946171052Sattilio rw->lock_object.lo_name, file, 947171052Sattilio line); 948171052Sattilio } else if (what & RA_RECURSED) 949171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 950171052Sattilio rw->lock_object.lo_name, file, line); 951171052Sattilio } 952154941Sjhb#endif 953154941Sjhb break; 954154941Sjhb case RA_WLOCKED: 955171052Sattilio case RA_WLOCKED | RA_RECURSED: 956171052Sattilio case RA_WLOCKED | RA_NOTRECURSED: 957157826Sjhb if (rw_wowner(rw) != curthread) 958154941Sjhb panic("Lock %s not exclusively locked @ %s:%d\n", 959167787Sjhb rw->lock_object.lo_name, file, line); 960171052Sattilio if (rw_recursed(rw)) { 961171052Sattilio if (what & RA_NOTRECURSED) 962171052Sattilio panic("Lock %s recursed @ %s:%d\n", 963171052Sattilio rw->lock_object.lo_name, file, line); 964171052Sattilio } else if (what & RA_RECURSED) 965171052Sattilio panic("Lock %s not recursed @ %s:%d\n", 966171052Sattilio rw->lock_object.lo_name, file, line); 967154941Sjhb break; 968154941Sjhb case RA_UNLOCKED: 969154941Sjhb#ifdef WITNESS 970167787Sjhb witness_assert(&rw->lock_object, what, file, line); 971154941Sjhb#else 972154941Sjhb /* 973154941Sjhb * If we hold a write lock fail. We can't reliably check 974154941Sjhb * to see if we hold a read lock or not. 975154941Sjhb */ 976157826Sjhb if (rw_wowner(rw) == curthread) 977154941Sjhb panic("Lock %s exclusively locked @ %s:%d\n", 978167787Sjhb rw->lock_object.lo_name, file, line); 979154941Sjhb#endif 980154941Sjhb break; 981154941Sjhb default: 982154941Sjhb panic("Unknown rw lock assertion: %d @ %s:%d", what, file, 983154941Sjhb line); 984154941Sjhb } 985154941Sjhb} 986154941Sjhb#endif /* INVARIANT_SUPPORT */ 987154941Sjhb 988154941Sjhb#ifdef DDB 989154941Sjhbvoid 990154941Sjhbdb_show_rwlock(struct lock_object *lock) 991154941Sjhb{ 992154941Sjhb struct rwlock *rw; 993154941Sjhb struct thread *td; 994154941Sjhb 995154941Sjhb rw = (struct rwlock *)lock; 996154941Sjhb 997154941Sjhb db_printf(" state: "); 998154941Sjhb if (rw->rw_lock == RW_UNLOCKED) 999154941Sjhb db_printf("UNLOCKED\n"); 1000169394Sjhb else if (rw->rw_lock == RW_DESTROYED) { 1001169394Sjhb db_printf("DESTROYED\n"); 1002169394Sjhb return; 1003169394Sjhb } else if (rw->rw_lock & RW_LOCK_READ) 1004167504Sjhb db_printf("RLOCK: %ju locks\n", 1005167504Sjhb (uintmax_t)(RW_READERS(rw->rw_lock))); 1006154941Sjhb else { 1007157826Sjhb td = rw_wowner(rw); 1008154941Sjhb db_printf("WLOCK: %p (tid %d, pid %d, \"%s\")\n", td, 1009173600Sjulian td->td_tid, td->td_proc->p_pid, td->td_name); 1010171052Sattilio if (rw_recursed(rw)) 1011171052Sattilio db_printf(" recursed: %u\n", rw->rw_recurse); 1012154941Sjhb } 1013154941Sjhb db_printf(" waiters: "); 1014154941Sjhb switch (rw->rw_lock & (RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS)) { 1015154941Sjhb case RW_LOCK_READ_WAITERS: 1016154941Sjhb db_printf("readers\n"); 1017154941Sjhb break; 1018154941Sjhb case RW_LOCK_WRITE_WAITERS: 1019154941Sjhb db_printf("writers\n"); 1020154941Sjhb break; 1021154941Sjhb case RW_LOCK_READ_WAITERS | RW_LOCK_WRITE_WAITERS: 1022167492Sjhb db_printf("readers and writers\n"); 1023154941Sjhb break; 1024154941Sjhb default: 1025154941Sjhb db_printf("none\n"); 1026154941Sjhb break; 1027154941Sjhb } 1028154941Sjhb} 1029154941Sjhb 1030154941Sjhb#endif 1031