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diff --git a/doc/ck_swlock b/doc/ck_swlock new file mode 100644 index 0000000..e101334 --- /dev/null +++ b/doc/ck_swlock @@ -0,0 +1,138 @@ +.\" +.\" Copyright 2014 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 April 22, 2014. +.Dt ck_swlock 3 +.Sh NAME +.Nm ck_swlock_init , +.Nm ck_swlock_write_latch , +.Nm ck_swlock_write_unlatch , +.Nm ck_swlock_write_lock , +.Nm ck_swlock_write_unlock , +.Nm ck_swlock_write_trylock , +.Nm ck_swlock_write_downgrade , +.Nm ck_swlock_locked_writer , +.Nm ck_swlock_read_lock , +.Nm ck_swlock_read_trylock , +.Nm ck_swlock_read_unlock , +.Nm ck_swlock_locked_reader +.Nd centralized copy-safe write-biased single-writer read-write locks +.Sh LIBRARY +Concurrency Kit (libck, \-lck) +.Sh SYNOPSIS +.In ck_swlock.h +.Pp +.Dv ck_swlock_t lock = CK_SWLOCK_INITIALIZER; +.Pp +.Ft void +.Fn ck_swlock_init "ck_swlock_t *lock" +.Ft void +.Fn ck_swlock_write_lock "ck_swlock_t *lock" +.Ft void +.Fn ck_swlock_write_unlock "ck_swlock_t *lock" +.Ft void +.Fn ck_swlatch_write_latch "ck_swlatch_t *latch" +.Ft void +.Fn ck_swlatch_write_unlatch "ck_swlatch_t *latch" +.Ft bool +.Fn ck_swlock_write_trylock "ck_swlock_t *lock" +.Ft bool +.Fn ck_swlock_write_downgrade "ck_swlock_t *lock" +.Ft bool +.Fn ck_swlock_locked_writer "ck_swlock_t *lock" +.Ft void +.Fn ck_swlock_read_lock "ck_swlock_t *lock" +.Ft bool +.Fn ck_swlock_read_trylock "ck_swlock_t *lock" +.Ft void +.Fn ck_swlock_read_unlock "ck_swlock_t *lock" +.Ft bool +.Fn ck_swlock_locked_reader "ck_swlock_t *lock" +.Sh DESCRIPTION +This is a centralized write-biased single-writer reader-writer lock. It +requires half the space that ck_rwlock does and has a low latency +fast path. The lock supports latch and unlatch operations that +allow it to be used in a copy-safe manner (reader-bits may be +over-written safely). +.Sh EXAMPLE +.Bd -literal -offset indent +#include <ck_swlock.h> + +static ck_swlock_t lock = CK_SWLOCK_INITIALIZER; + +static void +reader(void) +{ + + for (;;) { + ck_swlock_read_lock(&lock); + /* Read-side critical section. */ + ck_swlock_read_unlock(&lock); + + if (ck_swlock_read_trylock(&lock) == true) { + /* Read-side critical section. */ + ck_swlock_read_unlock(&lock); + } + } + + return; +} + +static void +writer(void) +{ + ck_swlock_t contrived; + + for (;;) { + ck_swlock_write_lock(&lock); + /* Write-side critical section. */ + ck_swlock_write_unlock(&lock); + + if (ck_swlock_write_trylock(&lock) == true) { + /* Write-side critical section. */ + ck_swlock_write_unlock(&lock); + } + + ck_swlock_write_latch(&lock); + /* Write-side critical section. */ + + /* This is safe to do with-in a latch. */ + contrived = lock; + lock = contrived; + ck_swlock_write_unlatch(&lock); + } + + return; +} +.Ed +.Sh SEE ALSO +.Xr ck_brlock 3 , +.Xr ck_elide 3 , +.Xr ck_pflock 3 , +.Xr ck_rwlock 3 , +.Xr ck_tflock 3 +.Pp +Additional information available at http://concurrencykit.org/ |