kern_rangelock.c

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    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 
  252 #ifdef INVARIANT_SUPPORT
  253 void
  254 _rangelock_cookie_assert(void *cookie, int what, const char *file, int line)
  255 {
  256         struct rl_q_entry *entry;
  257         int flags;
  258 
  259         MPASS(cookie != NULL);
  260         entry = cookie;
  261         flags = entry->rl_q_flags;
  262         switch (what) {
  263         case RCA_LOCKED:
  264                 if ((flags & RL_LOCK_GRANTED) == 0)
  265                         panic("rangelock not held @ %s:%d\n", file, line);
  266                 break;
  267         case RCA_RLOCKED:
  268                 if ((flags & (RL_LOCK_GRANTED | RL_LOCK_READ)) !=
  269                     (RL_LOCK_GRANTED | RL_LOCK_READ))
  270                         panic("rangelock not rlocked @ %s:%d\n", file, line);
  271                 break;
  272         case RCA_WLOCKED:
  273                 if ((flags & (RL_LOCK_GRANTED | RL_LOCK_WRITE)) !=
  274                     (RL_LOCK_GRANTED | RL_LOCK_WRITE))
  275                         panic("rangelock not wlocked @ %s:%d\n", file, line);
  276                 break;
  277         default:
  278                 panic("Unknown rangelock assertion: %d @ %s:%d", what, file,
  279                     line);
  280         }
  281 }
  282 #endif  /* INVARIANT_SUPPORT */

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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_rangelock.c

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_rangelock.c