kern_rangelock.c revision 236317
1/*- 2 * Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org> 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice unmodified, this list of conditions, and the following 10 * disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27#include <sys/cdefs.h> 28__FBSDID("$FreeBSD: head/sys/kern/kern_rangelock.c 236317 2012-05-30 16:06:38Z kib $"); 29 30#include <sys/param.h> 31#include <sys/kernel.h> 32#include <sys/lock.h> 33#include <sys/mutex.h> 34#include <sys/proc.h> 35#include <sys/rangelock.h> 36#include <sys/systm.h> 37 38#include <vm/uma.h> 39 40struct rl_q_entry { 41 TAILQ_ENTRY(rl_q_entry) rl_q_link; 42 off_t rl_q_start, rl_q_end; 43 int rl_q_flags; 44}; 45 46static uma_zone_t rl_entry_zone; 47 48static void 49rangelock_sys_init(void) 50{ 51 52 rl_entry_zone = uma_zcreate("rl_entry", sizeof(struct rl_q_entry), 53 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 54} 55SYSINIT(vfs, SI_SUB_LOCK, SI_ORDER_ANY, rangelock_sys_init, NULL); 56 57static struct rl_q_entry * 58rlqentry_alloc(void) 59{ 60 61 return (uma_zalloc(rl_entry_zone, M_WAITOK)); 62} 63 64void 65rlqentry_free(struct rl_q_entry *rleq) 66{ 67 68 uma_zfree(rl_entry_zone, rleq); 69} 70 71void 72rangelock_init(struct rangelock *lock) 73{ 74 75 TAILQ_INIT(&lock->rl_waiters); 76 lock->rl_currdep = NULL; 77} 78 79void 80rangelock_destroy(struct rangelock *lock) 81{ 82 83 KASSERT(TAILQ_EMPTY(&lock->rl_waiters), ("Dangling waiters")); 84} 85 86/* 87 * Verifies the supplied rl_q_entries for compatibility. Returns true 88 * if the rangelock queue entries are not compatible, false if they are. 89 * 90 * Two entries are compatible if their ranges do not overlap, or both 91 * entries are for read. 92 */ 93static int 94rangelock_incompatible(const struct rl_q_entry *e1, 95 const struct rl_q_entry *e2) 96{ 97 98 if ((e1->rl_q_flags & RL_LOCK_TYPE_MASK) == RL_LOCK_READ && 99 (e2->rl_q_flags & RL_LOCK_TYPE_MASK) == RL_LOCK_READ) 100 return (0); 101 if (e1->rl_q_start < e2->rl_q_end && e1->rl_q_end > e2->rl_q_start) 102 return (1); 103 return (0); 104} 105 106/* 107 * Recalculate the lock->rl_currdep after an unlock. 108 */ 109static void 110rangelock_calc_block(struct rangelock *lock) 111{ 112 struct rl_q_entry *entry, *entry1, *whead; 113 114 if (lock->rl_currdep == TAILQ_FIRST(&lock->rl_waiters) && 115 lock->rl_currdep != NULL) 116 lock->rl_currdep = TAILQ_NEXT(lock->rl_currdep, rl_q_link); 117 for (entry = lock->rl_currdep; entry != NULL; 118 entry = TAILQ_NEXT(entry, rl_q_link)) { 119 TAILQ_FOREACH(entry1, &lock->rl_waiters, rl_q_link) { 120 if (rangelock_incompatible(entry, entry1)) 121 goto out; 122 if (entry1 == entry) 123 break; 124 } 125 } 126out: 127 lock->rl_currdep = entry; 128 TAILQ_FOREACH(whead, &lock->rl_waiters, rl_q_link) { 129 if (whead == lock->rl_currdep) 130 break; 131 if (!(whead->rl_q_flags & RL_LOCK_GRANTED)) { 132 whead->rl_q_flags |= RL_LOCK_GRANTED; 133 wakeup(whead); 134 } 135 } 136} 137 138static void 139rangelock_unlock_locked(struct rangelock *lock, struct rl_q_entry *entry, 140 struct mtx *ilk) 141{ 142 143 MPASS(lock != NULL && entry != NULL && ilk != NULL); 144 mtx_assert(ilk, MA_OWNED); 145 KASSERT(entry != lock->rl_currdep, ("stuck currdep")); 146 147 TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link); 148 rangelock_calc_block(lock); 149 mtx_unlock(ilk); 150 if (curthread->td_rlqe == NULL) 151 curthread->td_rlqe = entry; 152 else 153 rlqentry_free(entry); 154} 155 156void 157rangelock_unlock(struct rangelock *lock, void *cookie, struct mtx *ilk) 158{ 159 160 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 161 162 mtx_lock(ilk); 163 rangelock_unlock_locked(lock, cookie, ilk); 164} 165 166/* 167 * Unlock the sub-range of granted lock. 168 */ 169void * 170rangelock_unlock_range(struct rangelock *lock, void *cookie, off_t start, 171 off_t end, struct mtx *ilk) 172{ 173 struct rl_q_entry *entry; 174 175 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 176 entry = cookie; 177 KASSERT(entry->rl_q_flags & RL_LOCK_GRANTED, 178 ("Unlocking non-granted lock")); 179 KASSERT(entry->rl_q_start == start, ("wrong start")); 180 KASSERT(entry->rl_q_end >= end, ("wrong end")); 181 182 mtx_lock(ilk); 183 if (entry->rl_q_end == end) { 184 rangelock_unlock_locked(lock, cookie, ilk); 185 return (NULL); 186 } 187 entry->rl_q_end = end; 188 rangelock_calc_block(lock); 189 mtx_unlock(ilk); 190 return (cookie); 191} 192 193/* 194 * Add the lock request to the queue of the pending requests for 195 * rangelock. Sleep until the request can be granted. 196 */ 197static void * 198rangelock_enqueue(struct rangelock *lock, off_t start, off_t end, int mode, 199 struct mtx *ilk) 200{ 201 struct rl_q_entry *entry; 202 struct thread *td; 203 204 MPASS(lock != NULL && ilk != NULL); 205 206 td = curthread; 207 if (td->td_rlqe != NULL) { 208 entry = td->td_rlqe; 209 td->td_rlqe = NULL; 210 } else 211 entry = rlqentry_alloc(); 212 MPASS(entry != NULL); 213 entry->rl_q_flags = mode; 214 entry->rl_q_start = start; 215 entry->rl_q_end = end; 216 217 mtx_lock(ilk); 218 /* 219 * XXXKIB TODO. Check that a thread does not try to enqueue a 220 * lock that is incompatible with another request from the same 221 * thread. 222 */ 223 224 TAILQ_INSERT_TAIL(&lock->rl_waiters, entry, rl_q_link); 225 if (lock->rl_currdep == NULL) 226 lock->rl_currdep = entry; 227 rangelock_calc_block(lock); 228 while (!(entry->rl_q_flags & RL_LOCK_GRANTED)) 229 msleep(entry, ilk, 0, "range", 0); 230 mtx_unlock(ilk); 231 return (entry); 232} 233 234void * 235rangelock_rlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 236{ 237 238 return (rangelock_enqueue(lock, start, end, RL_LOCK_READ, ilk)); 239} 240 241void * 242rangelock_wlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 243{ 244 245 return (rangelock_enqueue(lock, start, end, RL_LOCK_WRITE, ilk)); 246} 247