Adding upstream version 0.6.0.
Signed-off-by: Daniel Baumann <daniel@debian.org>
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doc/ck_spinlock
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doc/ck_spinlock
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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_spinlock 3
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.Sh NAME
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.Nm ck_spinlock_init ,
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.Nm ck_spinlock_lock ,
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.Nm ck_spinlock_unlock ,
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.Nm ck_spinlock_locked ,
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.Nm ck_spinlock_trylock ,
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.Nm ck_spinlock_anderson_init ,
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.Nm ck_spinlock_anderson_locked ,
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.Nm ck_spinlock_anderson_lock ,
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.Nm ck_spinlock_anderson_unlock ,
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.Nm ck_spinlock_cas_init ,
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.Nm ck_spinlock_cas_locked ,
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.Nm ck_spinlock_cas_lock ,
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.Nm ck_spinlock_cas_lock_eb ,
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.Nm ck_spinlock_cas_trylock ,
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.Nm ck_spinlock_cas_unlock ,
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.Nm ck_spinlock_clh_init ,
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.Nm ck_spinlock_clh_locked ,
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.Nm ck_spinlock_clh_lock ,
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.Nm ck_spinlock_clh_unlock ,
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.Nm ck_spinlock_dec_init ,
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.Nm ck_spinlock_dec_locked ,
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.Nm ck_spinlock_dec_lock ,
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.Nm ck_spinlock_dec_lock_eb ,
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.Nm ck_spinlock_dec_trylock ,
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.Nm ck_spinlock_dec_unlock ,
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.Nm ck_spinlock_fas_init ,
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.Nm ck_spinlock_fas_lock ,
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.Nm ck_spinlock_fas_lock_eb ,
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.Nm ck_spinlock_fas_locked ,
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.Nm ck_spinlock_fas_trylock ,
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.Nm ck_spinlock_fas_unlock ,
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.Nm ck_spinlock_hclh_init ,
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.Nm ck_spinlock_hclh_locked ,
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.Nm ck_spinlock_hclh_lock ,
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.Nm ck_spinlock_hclh_unlock ,
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.Nm ck_spinlock_mcs_init ,
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.Nm ck_spinlock_mcs_locked ,
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.Nm ck_spinlock_mcs_lock ,
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.Nm ck_spinlock_mcs_trylock ,
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.Nm ck_spinlock_mcs_unlock ,
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.Nm ck_spinlock_ticket_init ,
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.Nm ck_spinlock_ticket_locked ,
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.Nm ck_spinlock_ticket_lock ,
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.Nm ck_spinlock_ticket_lock_pb ,
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.Nm ck_spinlock_ticket_trylock ,
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.Nm ck_spinlock_ticket_unlock
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.Nd spinlock implementations
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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_spinlock.h
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.Pp
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.Dv ck_spinlock_t spinlock = CK_SPINLOCK_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_init "ck_spinlock_t *lock"
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.Ft void
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.Fn ck_spinlock_lock "ck_spinlock_t *lock"
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.Ft void
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.Fn ck_spinlock_unlock "ck_spinlock_t *lock"
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.Ft bool
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.Fn ck_spinlock_locked "ck_spinlock_t *lock"
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.Ft bool
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.Fn ck_spinlock_trylock "ck_spinlock_t *lock"
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.Ft void
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.Fn ck_spinlock_anderson_init "ck_spinlock_anderson_t *lock" "ck_spinlock_anderson_thread_t *slots" "unsigned int count"
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.Ft bool
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.Fn ck_spinlock_anderson_locked "ck_spinlock_anderson_t *lock"
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.Ft void
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.Fn ck_spinlock_anderson_lock "ck_spinlock_anderson_t *lock" "ck_spinlock_anderson_thread_t **slot"
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.Ft void
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.Fn ck_spinlock_anderson_unlock "ck_spinlock_anderson_t *lock" "ck_spinlock_anderson_thread_t *slot"
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.Pp
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.Dv ck_spinlock_cas_t spinlock = CK_SPINLOCK_CAS_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_cas_init "ck_spinlock_cas_t *lock"
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.Ft bool
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.Fn ck_spinlock_cas_locked "ck_spinlock_cas_t *lock"
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.Ft void
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.Fn ck_spinlock_cas_lock "ck_spinlock_cas_t *lock"
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.Ft void
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.Fn ck_spinlock_cas_lock_eb "ck_spinlock_cas_t *lock"
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.Ft bool
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.Fn ck_spinlock_cas_trylock "ck_spinlock_cas_t *lock"
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.Ft void
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.Fn ck_spinlock_cas_unlock "ck_spinlock_cas_t *lock"
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.Ft void
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.Fn ck_spinlock_clh_init "ck_spinlock_clh_t **lock" "ck_spinlock_clh_t *unowned"
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.Ft bool
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.Fn ck_spinlock_clh_locked "ck_spinlock_clh_t **lock"
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.Ft void
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.Fn ck_spinlock_clh_lock "ck_spinlock_clh_t **lock" "ck_spinlock_clh_t *node"
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.Ft void
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.Fn ck_spinlock_clh_unlock "ck_spinlock_clh_t **node"
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.Pp
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.Dv ck_spinlock_dec_t spinlock = CK_SPINLOCK_DEC_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_dec_init "ck_spinlock_dec_t *lock"
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.Ft bool
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.Fn ck_spinlock_dec_locked "ck_spinlock_dec_t *lock"
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.Ft void
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.Fn ck_spinlock_dec_lock "ck_spinlock_dec_t *lock"
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.Ft void
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.Fn ck_spinlock_dec_lock_eb "ck_spinlock_dec_t *lock"
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.Ft bool
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.Fn ck_spinlock_dec_trylock "ck_spinlock_dec_t *lock"
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.Ft void
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.Fn ck_spinlock_dec_unlock "ck_spinlock_dec_t *lock"
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.Pp
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.Dv ck_spinlock_fas_t spinlock = CK_SPINLOCK_FAS_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_fas_init "ck_spinlock_fas_t *lock"
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.Ft void
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.Fn ck_spinlock_fas_lock "ck_spinlock_fas_t *lock"
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.Ft void
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.Fn ck_spinlock_fas_lock_eb "ck_spinlock_fas_t *lock"
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.Ft bool
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.Fn ck_spinlock_fas_locked "ck_spinlock_fas_t *lock"
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.Ft bool
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.Fn ck_spinlock_fas_trylock "ck_spinlock_fas_t *lock"
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.Ft void
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.Fn ck_spinlock_fas_unlock "ck_spinlock_fas_t *lock"
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.Pp
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.Ft void
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.Fn ck_spinlock_hclh_init "ck_spinlock_hclh_t **lock" "ck_spinlock_hclh_t *unowned"
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.Ft bool
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.Fn ck_spinlock_hclh_locked "ck_spinlock_hclh_t **lock"
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.Ft void
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.Fn ck_spinlock_hclh_lock "ck_spinlock_hclh_t **lock" "ck_spinlock_hclh_t *node"
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.Ft void
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.Fn ck_spinlock_hclh_unlock "ck_spinlock_hclh_t **node"
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.Pp
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.Dv ck_spinlock_mcs_t spinlock = CK_SPINLOCK_MCS_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_mcs_init "ck_spinlock_mcs_t **lock"
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.Ft bool
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.Fn ck_spinlock_mcs_locked "ck_spinlock_mcs_t **lock"
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.Ft void
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.Fn ck_spinlock_mcs_lock "ck_spinlock_mcs_t **lock" "ck_spinlock_mcs_t *node"
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.Ft bool
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.Fn ck_spinlock_mcs_trylock "ck_spinlock_mcs_t **lock" "ck_spinlock_mcs_t *node"
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.Ft void
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.Fn ck_spinlock_mcs_unlock "ck_spinlock_mcs_t **lock" "ck_spinlock_mcs_t *node"
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.Pp
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.Dv ck_spinlock_ticket_t spinlock = CK_SPINLOCK_TICKET_INITIALIZER;
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.Ft void
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.Fn ck_spinlock_ticket_init "ck_spinlock_ticket_t *lock"
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.Ft bool
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.Fn ck_spinlock_ticket_locked "ck_spinlock_ticket_t *lock"
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.Ft void
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.Fn ck_spinlock_ticket_lock "ck_spinlock_ticket_t *lock"
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.Ft void
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.Fn ck_spinlock_ticket_lock_pb "ck_spinlock_ticket_t *lock" "unsigned int period"
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.Ft bool
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.Fn ck_spinlock_ticket_trylock "ck_spinlock_ticket_t *lock"
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.Ft void
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.Fn ck_spinlock_ticket_unlock "ck_spinlock_ticket_t *lock"
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.Sh DESCRIPTION
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A family of busy-wait spinlock implementations. The ck_spinlock_t implementation is simply
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a wrapper around the fetch-and-swap (ck_spinlock_fas_t) implementation. The table below
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provides a summary of the current implementations.
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.Bd -literal
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| Namespace | Algorithm | Type | Restrictions | Fair |
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\'----------------------|-----------------------------|---------------|-------------------------|--------'
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ck_spinlock_anderson Anderson Array Fixed number of threads Yes
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ck_spinlock_cas Compare-and-Swap Centralized None No
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ck_spinlock_clh Craig, Landin and Hagersten Queue Lifetime requirements Yes
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ck_spinlock_dec Decrement (Linux kernel) Centralized UINT_MAX concurrency No
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ck_spinlock_fas Fetch-and-store Centralized None No
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ck_spinlock_hclh Hierarchical CLH Queue Lifetime requirements Yes *
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ck_spinlock_mcs Mellor-Crummey and Scott Queue None Yes
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ck_spinlock_ticket Ticket Centralized None Yes
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.Ed
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.Pp
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* Hierarchical CLH only offers weak fairness for threads accross cluster
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nodes.
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.Pp
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If contention is low and there is no hard requirement for starvation-freedom
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then a centralized greedy (unfair) spinlock is recommended. If contention is
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high and there is no requirement for starvation-freedom then a centralized
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greedy spinlock is recommended to be used with an exponential backoff
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mechanism. If contention is generally low and there is a hard requirement for
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starvation-freedom then the ticket lock is recommended. If contention is high
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and there is a hard requirement for starvation-freedom then the Craig and
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Landin and Hagersten queue spinlock is recommended unless stack allocation is
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necessary or NUMA factor is high, in which case the Mellor-Crummey and Scott
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spinlock is recommended. If you cannot afford O(n) space-usage from array
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or queue spinlocks but still require fairness under high contention then
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the ticket lock with proportional back-off is recommended.
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If NUMA factor is high but prefer a greedy lock, then please see
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.Xr ck_cohort 3 .
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.Sh EXAMPLE
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.Bd -literal -offset indent
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#include <ck_spinlock.h>
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#include <stdbool.h>
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/*
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* Alternatively, the mutex may be initialized at run-time with
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* ck_spinlock_init(&mutex).
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*/
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ck_spinlock_t mutex = CK_SPINLOCK_INITIALIZER;
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void
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example(void)
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{
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ck_spinlock_lock(&mutex);
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/*
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* Critical section.
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*/
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ck_spinlock_unlock(&mutex);
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ck_spinlock_lock_eb(&mutex);
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/*
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* Critical section.
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*/
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ck_spinlock_unlock(&mutex);
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if (ck_spinlock_trylock(&mutex) == true) {
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/*
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* Critical section.
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*/
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ck_spinlock_unlock(&mutex);
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}
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}
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.Ed
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.Sh SEE ALSO
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.Xr ck_cohort 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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