sys/kern/kern_rangelock.c

   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 }