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129 lines
3.8 KiB
129 lines
3.8 KiB
11 years ago
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.\"
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.\" Copyright 2013 Samy Al Bahra.
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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, this list of conditions and the following 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 REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\"
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.Dd July 26, 2013.
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.Dt ck_rwlock 3
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.Sh NAME
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.Nm ck_rwlock
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.Nd centralized write-biased reader-writer locks
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.Sh LIBRARY
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Concurrency Kit (libck, \-lck)
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.Sh SYNOPSIS
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.In ck_rwlock.h
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.Pp
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.Dv ck_rwlock_t lock = CK_RWLOCK_INITIALIZER;
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.Pp
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.Ft void
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.Fn ck_rwlock_init "ck_rwlock_t *lock"
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.Ft void
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.Fn ck_rwlock_write_lock "ck_rwlock_t *lock"
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.Ft void
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.Fn ck_rwlock_write_unlock "ck_rwlock_t *lock"
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.Ft bool
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.Fn ck_rwlock_write_trylock "ck_rwlock_t *lock"
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.Ft bool
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.Fn ck_rwlock_write_downgrade "ck_rwlock_t *lock"
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.Ft bool
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.Fn ck_rwlock_locked_writer "ck_rwlock_t *lock"
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.Ft void
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.Fn ck_rwlock_read_lock "ck_rwlock_t *lock"
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.Ft bool
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.Fn ck_rwlock_read_trylock "ck_rwlock_t *lock"
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.Ft void
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.Fn ck_rwlock_read_unlock "ck_rwlock_t *lock"
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.Ft bool
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.Fn ck_rwlock_locked_reader "ck_rwlock_t *lock"
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.Pp
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.Dv ck_rwlock_recursive_t lock = CK_RWLOCK_RECURSIVE_INITIALIZER;
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.Pp
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.Ft void
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.Fn ck_rwlock_recursive_write_lock "ck_rwlock_recursive_t *lock" "unsigned int tid"
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.Ft bool
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.Fn ck_rwlock_recursive_write_trylock "ck_rwlock_recursive_t *lock" "unsigned int tid"
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.Ft void
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.Fn ck_rwlock_recurisve_write_unlock "ck_rwlock_recursive_t *lock"
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.Ft void
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.Fn ck_rwlock_recursive_read_lock "ck_rwlock_recursive_t *lock"
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.Ft bool
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.Fn ck_rwlock_recursive_read_trylock "ck_rwlock_recursive_t *lock"
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.Ft void
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.Fn ck_rwlock_recursive_read_unlock "ck_rwlock_recursive_t *lock"
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.Sh DESCRIPTION
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This is a centralized write-biased reader-writer lock. It
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requires very little space overhead and has a low latency
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fast path. Write-side recursion requires usage of ck_rwlock_recursive.
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Read-side recursion is disallowed. The
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.Fn ck_rwlock_write_downgrade
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function degrades the caller's write-side acquisition to a read-side
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acquisition without forfeit of current critical section.
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.Sh EXAMPLE
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.Bd -literal -offset indent
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#include <ck_rwlock.h>
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static ck_rwlock_t lock = CK_RWLOCK_INITIALIZER;
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static void
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reader(void)
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{
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for (;;) {
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ck_rwlock_read_lock(&lock);
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/* Read-side critical section. */
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ck_rwlock_read_unlock(&lock);
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if (ck_rwlock_read_trylock(&lock) == true) {
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/* Read-side critical section. */
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ck_rwlock_read_unlock(&lock);
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}
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}
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return;
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}
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static void
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writer(void)
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{
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for (;;) {
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ck_rwlock_write_lock(&lock);
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/* Write-side critical section. */
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ck_rwlock_write_unlock(&lock);
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if (ck_rwlock_write_trylock(&lock, 1) == true) {
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/* Write-side critical section. */
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ck_rwlock_write_unlock(&lock);
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}
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}
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return;
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}
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.Ed
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.Sh SEE ALSO
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.Xr ck_brlock 3 ,
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.Xr ck_elide 3
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.Pp
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Additional information available at http://concurrencykit.org/
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