1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice unmodified, this list of conditions, and the following 12 * disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <sys/param.h> 33 #include <sys/kernel.h> 34 #include <sys/lock.h> 35 #include <sys/mutex.h> 36 #include <sys/proc.h> 37 #include <sys/rangelock.h> 38 #include <sys/systm.h> 39 40 #include <vm/uma.h> 41 42 struct rl_q_entry { 43 TAILQ_ENTRY(rl_q_entry) rl_q_link; 44 off_t rl_q_start, rl_q_end; 45 int rl_q_flags; 46 }; 47 48 static uma_zone_t rl_entry_zone; 49 50 static void 51 rangelock_sys_init(void) 52 { 53 54 rl_entry_zone = uma_zcreate("rl_entry", sizeof(struct rl_q_entry), 55 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 56 } 57 SYSINIT(vfs, SI_SUB_LOCK, SI_ORDER_ANY, rangelock_sys_init, NULL); 58 59 static struct rl_q_entry * 60 rlqentry_alloc(void) 61 { 62 63 return (uma_zalloc(rl_entry_zone, M_WAITOK)); 64 } 65 66 void 67 rlqentry_free(struct rl_q_entry *rleq) 68 { 69 70 uma_zfree(rl_entry_zone, rleq); 71 } 72 73 void 74 rangelock_init(struct rangelock *lock) 75 { 76 77 TAILQ_INIT(&lock->rl_waiters); 78 lock->rl_currdep = NULL; 79 } 80 81 void 82 rangelock_destroy(struct rangelock *lock) 83 { 84 85 KASSERT(TAILQ_EMPTY(&lock->rl_waiters), ("Dangling waiters")); 86 } 87 88 /* 89 * Two entries are compatible if their ranges do not overlap, or both 90 * entries are for read. 91 */ 92 static int 93 ranges_overlap(const struct rl_q_entry *e1, 94 const struct rl_q_entry *e2) 95 { 96 97 if (e1->rl_q_start < e2->rl_q_end && e1->rl_q_end > e2->rl_q_start) 98 return (1); 99 return (0); 100 } 101 102 /* 103 * Recalculate the lock->rl_currdep after an unlock. 104 */ 105 static void 106 rangelock_calc_block(struct rangelock *lock) 107 { 108 struct rl_q_entry *entry, *nextentry, *entry1; 109 110 for (entry = lock->rl_currdep; entry != NULL; entry = nextentry) { 111 nextentry = TAILQ_NEXT(entry, rl_q_link); 112 if (entry->rl_q_flags & RL_LOCK_READ) { 113 /* Reads must not overlap with granted writes. */ 114 for (entry1 = TAILQ_FIRST(&lock->rl_waiters); 115 !(entry1->rl_q_flags & RL_LOCK_READ); 116 entry1 = TAILQ_NEXT(entry1, rl_q_link)) { 117 if (ranges_overlap(entry, entry1)) 118 goto out; 119 } 120 } else { 121 /* Write must not overlap with any granted locks. */ 122 for (entry1 = TAILQ_FIRST(&lock->rl_waiters); 123 entry1 != entry; 124 entry1 = TAILQ_NEXT(entry1, rl_q_link)) { 125 if (ranges_overlap(entry, entry1)) 126 goto out; 127 } 128 129 /* Move grantable write locks to the front. */ 130 TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link); 131 TAILQ_INSERT_HEAD(&lock->rl_waiters, entry, rl_q_link); 132 } 133 134 /* Grant this lock. */ 135 entry->rl_q_flags |= RL_LOCK_GRANTED; 136 wakeup(entry); 137 } 138 out: 139 lock->rl_currdep = entry; 140 } 141 142 static void 143 rangelock_unlock_locked(struct rangelock *lock, struct rl_q_entry *entry, 144 struct mtx *ilk) 145 { 146 147 MPASS(lock != NULL && entry != NULL && ilk != NULL); 148 mtx_assert(ilk, MA_OWNED); 149 KASSERT(entry != lock->rl_currdep, ("stuck currdep")); 150 151 TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link); 152 rangelock_calc_block(lock); 153 mtx_unlock(ilk); 154 if (curthread->td_rlqe == NULL) 155 curthread->td_rlqe = entry; 156 else 157 rlqentry_free(entry); 158 } 159 160 void 161 rangelock_unlock(struct rangelock *lock, void *cookie, struct mtx *ilk) 162 { 163 164 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 165 166 mtx_lock(ilk); 167 rangelock_unlock_locked(lock, cookie, ilk); 168 } 169 170 /* 171 * Unlock the sub-range of granted lock. 172 */ 173 void * 174 rangelock_unlock_range(struct rangelock *lock, void *cookie, off_t start, 175 off_t end, struct mtx *ilk) 176 { 177 struct rl_q_entry *entry; 178 179 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 180 entry = cookie; 181 KASSERT(entry->rl_q_flags & RL_LOCK_GRANTED, 182 ("Unlocking non-granted lock")); 183 KASSERT(entry->rl_q_start == start, ("wrong start")); 184 KASSERT(entry->rl_q_end >= end, ("wrong end")); 185 186 mtx_lock(ilk); 187 if (entry->rl_q_end == end) { 188 rangelock_unlock_locked(lock, cookie, ilk); 189 return (NULL); 190 } 191 entry->rl_q_end = end; 192 rangelock_calc_block(lock); 193 mtx_unlock(ilk); 194 return (cookie); 195 } 196 197 /* 198 * Add the lock request to the queue of the pending requests for 199 * rangelock. Sleep until the request can be granted. 200 */ 201 static void * 202 rangelock_enqueue(struct rangelock *lock, off_t start, off_t end, int mode, 203 struct mtx *ilk) 204 { 205 struct rl_q_entry *entry; 206 struct thread *td; 207 208 MPASS(lock != NULL && ilk != NULL); 209 210 td = curthread; 211 if (td->td_rlqe != NULL) { 212 entry = td->td_rlqe; 213 td->td_rlqe = NULL; 214 } else 215 entry = rlqentry_alloc(); 216 MPASS(entry != NULL); 217 entry->rl_q_flags = mode; 218 entry->rl_q_start = start; 219 entry->rl_q_end = end; 220 221 mtx_lock(ilk); 222 /* 223 * XXXKIB TODO. Check that a thread does not try to enqueue a 224 * lock that is incompatible with another request from the same 225 * thread. 226 */ 227 228 TAILQ_INSERT_TAIL(&lock->rl_waiters, entry, rl_q_link); 229 if (lock->rl_currdep == NULL) 230 lock->rl_currdep = entry; 231 rangelock_calc_block(lock); 232 while (!(entry->rl_q_flags & RL_LOCK_GRANTED)) 233 msleep(entry, ilk, 0, "range", 0); 234 mtx_unlock(ilk); 235 return (entry); 236 } 237 238 void * 239 rangelock_rlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 240 { 241 242 return (rangelock_enqueue(lock, start, end, RL_LOCK_READ, ilk)); 243 } 244 245 void * 246 rangelock_wlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 247 { 248 249 return (rangelock_enqueue(lock, start, end, RL_LOCK_WRITE, ilk)); 250 } 251