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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 13, 2013.
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.Dt ck_elide 3
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.Sh NAME
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.Nm CK_ELIDE_PROTOTYPE CK_ELIDE_LOCK_ADAPTIVE CK_ELIDE_UNLOCK_ADAPTIVE CK_ELIDE_LOCK CK_ELIDE_UNLOCK CK_ELIDE_TRYLOCK_PROTOTYPE CK_ELIDE_TRYLOCK
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.Nd lock elision wrappers
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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_elide.h
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.Pp
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.Dv ck_elide_stat_t stat = CK_ELIDE_STAT_INITIALIZER;
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.Pp
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.Ft void
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.Fn ck_elide_stat_init "ck_elide_stat_t *"
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.Pp
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.Dv struct ck_elide_config config = CK_ELIDE_CONFIG_DEFAULT_INITIALIZER;
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.Pp
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.Bd -literal -offset
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struct ck_elide_config {
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unsigned short skip_busy;
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short retry_busy;
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unsigned short skip_other;
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short retry_other;
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unsigned short skip_conflict;
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short retry_conflict;
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};
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.Ed
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.Pp
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.Fn CK_ELIDE_PROTOTYPE "NAME" "TYPE" "LOCK_PREDICATE" "LOCK_FUNCTION" "UNLOCK_PREDICATE" "UNLOCK_FUNCTION"
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.Fn CK_ELIDE_LOCK_ADAPTIVE "NAME" "ck_elide_stat_t *" "struct ck_elide_config *" "TYPE *"
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.Fn CK_ELIDE_UNLOCK_ADAPTIVE "NAME" "ck_elide_stat_t *" "TYPE *"
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.Fn CK_ELIDE_LOCK "NAME" "TYPE *"
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.Fn CK_ELIDE_UNLOCK "NAME" "TYPE *"
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.Fn CK_ELIDE_TRYLOCK_PROTOTYPE "NAME" "TYPE" "LOCK_PREDICATE" "TRYLOCK_FUNCTION"
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.Sh DESCRIPTION
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These macros implement lock elision wrappers for a user-specified single-argument
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lock interface. The wrappers will attempt to elide lock acquisition, allowing
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concurrent execution of critical sections that do not issue conflicting memory
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operations. If any threads have successfully elided a lock acquisition,
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conflicting memory operations will roll-back any side-effects of the critical
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section and force every thread to retry the lock acquisition regularly.
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.Fn CK_ELIDE_LOCK ,
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.Fn CK_ELIDE_UNLOCK ,
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.Fn CK_ELIDE_LOCK_ADAPTIVE ,
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and
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.Fn CK_ELIDE_UNLOCK_ADAPTIVE
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macros require
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a previous
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.Fn CK_ELIDE_PROTOTYPE
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with the same
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.Fa NAME .
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Elision is attempted if the
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.Fa LOCK_PREDICATE
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function returns false. If
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.Fa LOCK_PREDICATE
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returns true then elision is aborted and
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.Fa LOCK_FUNCTION
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is executed instead. If any threads are in an elided critical section,
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.Fa LOCK_FUNCTION
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must force them to rollback through a conflicting memory operation.
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The
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.Fa UNLOCK_PREDICATE
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function must return true if the lock is acquired by the caller, meaning
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that the lock was not successfully elided. If
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.Fa UNLOCK_PREDICATE
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returns true, then the
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.Fa UNLOCK_FUNCTION
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is executed. If RTM is unsupported (no CK_F_PR_RTM macro) then
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.Fn CK_ELIDE_LOCK
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and
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.Fn CK_ELIDE_LOCK_ADAPTIVE
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will immediately call
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.Fn LOCK_FUNCTION .
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.Fn CK_ELIDE_UNLOCK
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and
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.Fn CK_ELIDE_UNLOCK_ADAPTIVE
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will immediately call
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.Fn UNLOCK_FUNCTION .
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.Fn CK_ELIDE_TRYLOCK
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requires a previous
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.Fn CK_ELIDE_TRYLOCK_PROTOTYPE
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with the same name.
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Elision is attempted if the
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.Fa LOCK_PREDICATE
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function returns false. If
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.Fa LOCK_PREDICATE
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returns true or if elision fails then the
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operation is aborted. If RTM is unsupported
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(no CK_F_PR_RTM macro) then
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.Fn CK_ELIDE_TRYLOCK
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will immediately call
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.Fn TRYLOCK_FUNCTION .
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.Fn CK_ELIDE_LOCK_ADAPTIVE
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and
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.Fn CK_ELIDE_UNLOCK_ADAPTIVE
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will adapt the elision behavior associated with lock operations
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according to the run-time behavior of the program. This behavior
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is defined by the ck_elide_config structure pointer passed to
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.Fn CK_ELIDE_LOCK_ADAPTIVE .
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A thread-local ck_elide_stat structure must be passed to both
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.Fn CK_ELIDE_LOCK_ADAPTIVE
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and
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.Fn CK_ELIDE_UNLOCK_ADAPTIVE .
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This structure is expected to be unique for different workloads,
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may not be re-used in recursive acquisitions and must match the
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lifetime of the lock it is associated with.
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Both ck_spinlock.h and ck_rwlock.h define ck_elide wrappers under
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the ck_spinlock and ck_rwlock namespace, respectively.
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.Sh SEE ALSO
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Additional information available at http://en.wikipedia.org/wiki/Transactional_Synchronization_Extensions and http://concurrencykit.org/
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