249 lines
6.2 KiB
C
249 lines
6.2 KiB
C
/*-
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* Copyright (c) 2009 Konstantin Belousov <kib@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/rangelock.h>
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#include <sys/systm.h>
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#include <vm/uma.h>
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struct rl_q_entry {
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TAILQ_ENTRY(rl_q_entry) rl_q_link;
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off_t rl_q_start, rl_q_end;
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int rl_q_flags;
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};
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static uma_zone_t rl_entry_zone;
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static void
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rangelock_sys_init(void)
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{
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rl_entry_zone = uma_zcreate("rl_entry", sizeof(struct rl_q_entry),
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NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
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}
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SYSINIT(vfs, SI_SUB_LOCK, SI_ORDER_ANY, rangelock_sys_init, NULL);
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static struct rl_q_entry *
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rlqentry_alloc(void)
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{
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return (uma_zalloc(rl_entry_zone, M_WAITOK));
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}
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void
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rlqentry_free(struct rl_q_entry *rleq)
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{
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uma_zfree(rl_entry_zone, rleq);
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}
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void
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rangelock_init(struct rangelock *lock)
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{
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TAILQ_INIT(&lock->rl_waiters);
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lock->rl_currdep = NULL;
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}
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void
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rangelock_destroy(struct rangelock *lock)
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{
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KASSERT(TAILQ_EMPTY(&lock->rl_waiters), ("Dangling waiters"));
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}
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/*
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* Two entries are compatible if their ranges do not overlap, or both
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* entries are for read.
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*/
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static int
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ranges_overlap(const struct rl_q_entry *e1,
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const struct rl_q_entry *e2)
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{
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if (e1->rl_q_start < e2->rl_q_end && e1->rl_q_end > e2->rl_q_start)
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return (1);
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return (0);
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}
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/*
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* Recalculate the lock->rl_currdep after an unlock.
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*/
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static void
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rangelock_calc_block(struct rangelock *lock)
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{
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struct rl_q_entry *entry, *nextentry, *entry1;
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for (entry = lock->rl_currdep; entry != NULL; entry = nextentry) {
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nextentry = TAILQ_NEXT(entry, rl_q_link);
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if (entry->rl_q_flags & RL_LOCK_READ) {
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/* Reads must not overlap with granted writes. */
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for (entry1 = TAILQ_FIRST(&lock->rl_waiters);
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!(entry1->rl_q_flags & RL_LOCK_READ);
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entry1 = TAILQ_NEXT(entry1, rl_q_link)) {
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if (ranges_overlap(entry, entry1))
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goto out;
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}
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} else {
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/* Write must not overlap with any granted locks. */
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for (entry1 = TAILQ_FIRST(&lock->rl_waiters);
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entry1 != entry;
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entry1 = TAILQ_NEXT(entry1, rl_q_link)) {
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if (ranges_overlap(entry, entry1))
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goto out;
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}
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/* Move grantable write locks to the front. */
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TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link);
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TAILQ_INSERT_HEAD(&lock->rl_waiters, entry, rl_q_link);
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}
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/* Grant this lock. */
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entry->rl_q_flags |= RL_LOCK_GRANTED;
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wakeup(entry);
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}
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out:
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lock->rl_currdep = entry;
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}
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static void
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rangelock_unlock_locked(struct rangelock *lock, struct rl_q_entry *entry,
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struct mtx *ilk)
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{
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MPASS(lock != NULL && entry != NULL && ilk != NULL);
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mtx_assert(ilk, MA_OWNED);
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KASSERT(entry != lock->rl_currdep, ("stuck currdep"));
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TAILQ_REMOVE(&lock->rl_waiters, entry, rl_q_link);
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rangelock_calc_block(lock);
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mtx_unlock(ilk);
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if (curthread->td_rlqe == NULL)
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curthread->td_rlqe = entry;
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else
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rlqentry_free(entry);
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}
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void
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rangelock_unlock(struct rangelock *lock, void *cookie, struct mtx *ilk)
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{
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MPASS(lock != NULL && cookie != NULL && ilk != NULL);
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mtx_lock(ilk);
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rangelock_unlock_locked(lock, cookie, ilk);
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}
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/*
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* Unlock the sub-range of granted lock.
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*/
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void *
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rangelock_unlock_range(struct rangelock *lock, void *cookie, off_t start,
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off_t end, struct mtx *ilk)
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{
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struct rl_q_entry *entry;
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MPASS(lock != NULL && cookie != NULL && ilk != NULL);
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entry = cookie;
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KASSERT(entry->rl_q_flags & RL_LOCK_GRANTED,
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("Unlocking non-granted lock"));
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KASSERT(entry->rl_q_start == start, ("wrong start"));
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KASSERT(entry->rl_q_end >= end, ("wrong end"));
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mtx_lock(ilk);
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if (entry->rl_q_end == end) {
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rangelock_unlock_locked(lock, cookie, ilk);
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return (NULL);
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}
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entry->rl_q_end = end;
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rangelock_calc_block(lock);
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mtx_unlock(ilk);
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return (cookie);
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}
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/*
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* Add the lock request to the queue of the pending requests for
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* rangelock. Sleep until the request can be granted.
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*/
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static void *
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rangelock_enqueue(struct rangelock *lock, off_t start, off_t end, int mode,
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struct mtx *ilk)
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{
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struct rl_q_entry *entry;
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struct thread *td;
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MPASS(lock != NULL && ilk != NULL);
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td = curthread;
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if (td->td_rlqe != NULL) {
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entry = td->td_rlqe;
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td->td_rlqe = NULL;
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} else
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entry = rlqentry_alloc();
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MPASS(entry != NULL);
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entry->rl_q_flags = mode;
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entry->rl_q_start = start;
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entry->rl_q_end = end;
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mtx_lock(ilk);
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/*
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* XXXKIB TODO. Check that a thread does not try to enqueue a
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* lock that is incompatible with another request from the same
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* thread.
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*/
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TAILQ_INSERT_TAIL(&lock->rl_waiters, entry, rl_q_link);
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if (lock->rl_currdep == NULL)
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lock->rl_currdep = entry;
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rangelock_calc_block(lock);
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while (!(entry->rl_q_flags & RL_LOCK_GRANTED))
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msleep(entry, ilk, 0, "range", 0);
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mtx_unlock(ilk);
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return (entry);
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}
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void *
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rangelock_rlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk)
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{
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return (rangelock_enqueue(lock, start, end, RL_LOCK_READ, ilk));
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}
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void *
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rangelock_wlock(struct rangelock *lock, off_t start, off_t end, struct mtx *ilk)
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{
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return (rangelock_enqueue(lock, start, end, RL_LOCK_WRITE, ilk));
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}
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