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114 lines
3.4 KiB
114 lines
3.4 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_brlock 3
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.Sh NAME
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.Nm ck_brlock
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.Nd big-reader 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_brlock.h
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.Pp
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.Dv ck_brlock_t brlock = CK_BRLOCK_INITIALIZER;
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.Pp
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.Dv ck_brlock_reader_t reader = CK_BRLOCK_READER_INITIALIZER;
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.Pp
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.Ft void
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.Fn ck_brlock_init "ck_brlock_t *br"
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.Ft void
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.Fn ck_brlock_write_lock "ck_brlock_t *br"
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.Ft void
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.Fn ck_brlock_write_unlock "ck_brlock_t *br"
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.Ft bool
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.Fn ck_brlock_write_trylock "ck_brlock_t *br" "unsigned int factor"
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.Ft void
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.Fn ck_brlock_read_register "ck_brlock_t *br" "ck_brlock_reader_t *reader"
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.Ft void
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.Fn ck_brlock_read_unregister "ck_brlock_t *br" "ck_brlock_reader_t *reader"
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.Ft void
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.Fn ck_brlock_read_lock "ck_brlock_t *br" "ck_brlock_reader_t *reader"
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.Ft bool
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.Fn ck_brlock_read_trylock "ck_brlock_t *br" "ck_brlock_reader_t *reader" \
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"unsigned int factor"
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.Ft void
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.Fn ck_brlock_read_unlock "ck_brlock_reader_t *reader"
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.Sh DESCRIPTION
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Big reader locks are distributed reader-writer locks with low latency constant time
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reader acquisition (with respect to number of concurrent readers). On the other
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hand, writer acquisitions are a relatively expensive O(n) operation. This is a write-biased
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lock.
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.Sh EXAMPLE
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.Bd -literal -offset indent
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static ck_brlock_t lock = CK_BRLOCK_INITIALIZER;
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static __thread ck_brlock_reader_t reader;
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static void
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reader(void)
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{
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/* Add our thread as a lock participant. */
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ck_brlock_read_register(&lock, &reader);
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for (;;) {
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ck_brlock_read_lock(&lock, &reader);
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/* Read-side critical section. */
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ck_brlock_read_unlock(&reader);
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if (ck_brlock_read_trylock(&lock, &reader, 1) == true) {
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/* Read-side critical section. */
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ck_brlock_read_unlock(&reader);
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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_brlock_write_lock(&lock);
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/* Write-side critical section. */
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ck_brlock_write_unlock(&lock);
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if (ck_brlock_write_trylock(&lock, 1) == true) {
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/* Write-side critical section. */
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ck_brlock_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_bytelock 3 ,
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.Xr ck_rwlock 3
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.Pp
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Additional information available at http://concurrencykit.org/
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