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("$FreeBSD$"); 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 40 struct 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 46 static uma_zone_t rl_entry_zone; 47 48 static void 49 rangelock_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 } 55 SYSINIT(vfs, SI_SUB_LOCK, SI_ORDER_ANY, rangelock_sys_init, NULL); 56 57 static struct rl_q_entry * 58 rlqentry_alloc(void) 59 { 60 61 return (uma_zalloc(rl_entry_zone, M_WAITOK)); 62 } 63 64 void 65 rlqentry_free(struct rl_q_entry *rleq) 66 { 67 68 uma_zfree(rl_entry_zone, rleq); 69 } 70 71 void 72 rangelock_init(struct rangelock *lock) 73 { 74 75 TAILQ_INIT(&lock->rl_waiters); 76 lock->rl_currdep = NULL; 77 } 78 79 void 80 rangelock_destroy(struct rangelock *lock) 81 { 82 83 KASSERT(TAILQ_EMPTY(&lock->rl_waiters), ("Dangling waiters")); 84 } 85 86 /* 87 * Two entries are compatible if their ranges do not overlap, or both 88 * entries are for read. 89 */ 90 static int 91 ranges_overlap(const struct rl_q_entry *e1, 92 const struct rl_q_entry *e2) 93 { 94 95 if (e1->rl_q_start < e2->rl_q_end && e1->rl_q_end > e2->rl_q_start) 96 return (1); 97 return (0); 98 } 99 100 /* 101 * Recalculate the lock->rl_currdep after an unlock. 102 */ 103 static void 104 rangelock_calc_block(struct rangelock *lock) 105 { 106 struct rl_q_entry *entry, *nextentry, *entry1; 107 108 for (entry = lock->rl_currdep; entry != NULL; entry = nextentry) { 109 nextentry = TAILQ_NEXT(entry, rl_q_link); 110 if (entry->rl_q_flags & RL_LOCK_READ) { 111 /* Reads must not overlap with granted writes. */ 112 for (entry1 = TAILQ_FIRST(&lock->rl_waiters); 113 !(entry1->rl_q_flags & RL_LOCK_READ); 114 entry1 = TAILQ_NEXT(entry1, rl_q_link)) { 115 if (ranges_overlap(entry, entry1)) 116 goto out; 117 } 118 } else { 119 /* Write must not overlap with any granted locks. */ 120 for (entry1 = TAILQ_FIRST(&lock->rl_waiters); 121 entry1 != entry; 122 entry1 = TAILQ_NEXT(entry1, rl_q_link)) { 123 if (ranges_overlap(entry, entry1)) 124 goto out; 125 } 126 127 /* Move grantable write locks to the front. */ 128 TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link); 129 TAILQ_INSERT_HEAD(&lock->rl_waiters, entry, rl_q_link); 130 } 131 132 /* Grant this lock. */ 133 entry->rl_q_flags |= RL_LOCK_GRANTED; 134 wakeup(entry); 135 } 136 out: 137 lock->rl_currdep = entry; 138 } 139 140 static void 141 rangelock_unlock_locked(struct rangelock *lock, struct rl_q_entry *entry, 142 struct mtx *ilk) 143 { 144 145 MPASS(lock != NULL && entry != NULL && ilk != NULL); 146 mtx_assert(ilk, MA_OWNED); 147 KASSERT(entry != lock->rl_currdep, ("stuck currdep")); 148 149 TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link); 150 rangelock_calc_block(lock); 151 mtx_unlock(ilk); 152 if (curthread->td_rlqe == NULL) 153 curthread->td_rlqe = entry; 154 else 155 rlqentry_free(entry); 156 } 157 158 void 159 rangelock_unlock(struct rangelock *lock, void *cookie, struct mtx *ilk) 160 { 161 162 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 163 164 mtx_lock(ilk); 165 rangelock_unlock_locked(lock, cookie, ilk); 166 } 167 168 /* 169 * Unlock the sub-range of granted lock. 170 */ 171 void * 172 rangelock_unlock_range(struct rangelock *lock, void *cookie, off_t start, 173 off_t end, struct mtx *ilk) 174 { 175 struct rl_q_entry *entry; 176 177 MPASS(lock != NULL && cookie != NULL && ilk != NULL); 178 entry = cookie; 179 KASSERT(entry->rl_q_flags & RL_LOCK_GRANTED, 180 ("Unlocking non-granted lock")); 181 KASSERT(entry->rl_q_start == start, ("wrong start")); 182 KASSERT(entry->rl_q_end >= end, ("wrong end")); 183 184 mtx_lock(ilk); 185 if (entry->rl_q_end == end) { 186 rangelock_unlock_locked(lock, cookie, ilk); 187 return (NULL); 188 } 189 entry->rl_q_end = end; 190 rangelock_calc_block(lock); 191 mtx_unlock(ilk); 192 return (cookie); 193 } 194 195 /* 196 * Add the lock request to the queue of the pending requests for 197 * rangelock. Sleep until the request can be granted. 198 */ 199 static void * 200 rangelock_enqueue(struct rangelock *lock, off_t start, off_t end, int mode, 201 struct mtx *ilk) 202 { 203 struct rl_q_entry *entry; 204 struct thread *td; 205 206 MPASS(lock != NULL && ilk != NULL); 207 208 td = curthread; 209 if (td->td_rlqe != NULL) { 210 entry = td->td_rlqe; 211 td->td_rlqe = NULL; 212 } else 213 entry = rlqentry_alloc(); 214 MPASS(entry != NULL); 215 entry->rl_q_flags = mode; 216 entry->rl_q_start = start; 217 entry->rl_q_end = end; 218 219 mtx_lock(ilk); 220 /* 221 * XXXKIB TODO. Check that a thread does not try to enqueue a 222 * lock that is incompatible with another request from the same 223 * thread. 224 */ 225 226 TAILQ_INSERT_TAIL(&lock->rl_waiters, entry, rl_q_link); 227 if (lock->rl_currdep == NULL) 228 lock->rl_currdep = entry; 229 rangelock_calc_block(lock); 230 while (!(entry->rl_q_flags & RL_LOCK_GRANTED)) 231 msleep(entry, ilk, 0, "range", 0); 232 mtx_unlock(ilk); 233 return (entry); 234 } 235 236 void * 237 rangelock_rlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 238 { 239 240 return (rangelock_enqueue(lock, start, end, RL_LOCK_READ, ilk)); 241 } 242 243 void * 244 rangelock_wlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk) 245 { 246 247 return (rangelock_enqueue(lock, start, end, RL_LOCK_WRITE, ilk)); 248 } 249