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diff --git a/doc/ck_brlock b/doc/ck_brlock new file mode 100644 index 0000000..7972ee4 --- /dev/null +++ b/doc/ck_brlock @@ -0,0 +1,121 @@ +.\" +.\" Copyright 2013 Samy Al Bahra. +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" +.Dd July 26, 2013. +.Dt ck_brlock 3 +.Sh NAME +.Nm ck_brlock_init , +.Nm ck_brlock_write_lock , +.Nm ck_brlock_write_unlock , +.Nm ck_brlock_write_trylock , +.Nm ck_brlock_read_register , +.Nm ck_brlock_read_unregister , +.Nm ck_brlock_read_lock , +.Nm ck_brlock_read_trylock , +.Nm ck_brlock_read_unlock +.Nd big-reader locks +.Sh LIBRARY +Concurrency Kit (libck, \-lck) +.Sh SYNOPSIS +.In ck_brlock.h +.Pp +.Dv ck_brlock_t brlock = CK_BRLOCK_INITIALIZER; +.Pp +.Dv ck_brlock_reader_t reader = CK_BRLOCK_READER_INITIALIZER; +.Pp +.Ft void +.Fn ck_brlock_init "ck_brlock_t *br" +.Ft void +.Fn ck_brlock_write_lock "ck_brlock_t *br" +.Ft void +.Fn ck_brlock_write_unlock "ck_brlock_t *br" +.Ft bool +.Fn ck_brlock_write_trylock "ck_brlock_t *br" "unsigned int factor" +.Ft void +.Fn ck_brlock_read_register "ck_brlock_t *br" "ck_brlock_reader_t *reader" +.Ft void +.Fn ck_brlock_read_unregister "ck_brlock_t *br" "ck_brlock_reader_t *reader" +.Ft void +.Fn ck_brlock_read_lock "ck_brlock_t *br" "ck_brlock_reader_t *reader" +.Ft bool +.Fn ck_brlock_read_trylock "ck_brlock_t *br" "ck_brlock_reader_t *reader" \ +"unsigned int factor" +.Ft void +.Fn ck_brlock_read_unlock "ck_brlock_reader_t *reader" +.Sh DESCRIPTION +Big reader locks are distributed reader-writer locks with low latency constant time +reader acquisition (with respect to number of concurrent readers). On the other +hand, writer acquisitions are a relatively expensive O(n) operation. This is a write-biased +lock. +.Sh EXAMPLE +.Bd -literal -offset indent +static ck_brlock_t lock = CK_BRLOCK_INITIALIZER; +static __thread ck_brlock_reader_t reader; + +static void +reader(void) +{ + + /* Add our thread as a lock participant. */ + ck_brlock_read_register(&lock, &reader); + + for (;;) { + ck_brlock_read_lock(&lock, &reader); + /* Read-side critical section. */ + ck_brlock_read_unlock(&reader); + + if (ck_brlock_read_trylock(&lock, &reader, 1) == true) { + /* Read-side critical section. */ + ck_brlock_read_unlock(&reader); + } + } + + return; +} + +static void +writer(void) +{ + + for (;;) { + ck_brlock_write_lock(&lock); + /* Write-side critical section. */ + ck_brlock_write_unlock(&lock); + + if (ck_brlock_write_trylock(&lock, 1) == true) { + /* Write-side critical section. */ + ck_brlock_write_unlock(&lock); + } + } + + return; +} +.Ed +.Sh SEE ALSO +.Xr ck_bytelock 3 , +.Xr ck_rwlock 3 +.Pp +Additional information available at http://concurrencykit.org/ |