2011-08-07 16:29:24 +04:00
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.\" $NetBSD: pserialize.9,v 1.3 2011/08/07 12:29:24 rmind Exp $
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2011-07-30 22:19:04 +04:00
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.\"
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.\" Copyright (c) 2011 The NetBSD Foundation, Inc.
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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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd July 30, 2011
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.Dt PSERIALIZE 9
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.Os
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.Sh NAME
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.Nm pserialize
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.Nd passive serialization mechanism
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.Sh SYNOPSIS
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.In sys/pserialize.h
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.Ft pserialize_t
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.Fn pserialize_create "void"
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.Ft void
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.Fn pserialize_destroy "pserialize_t psz"
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.Ft int
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.Fn pserialize_read_enter "void"
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.Ft void
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.Fn pserialize_read_exit "int s"
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.Ft void
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.Fn pserialize_perform "pserialize_t psz"
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.\" -----
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.Sh DESCRIPTION
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Passive serialization is a reader / writer synchronisation mechanism
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designed for lock-less read operations.
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The read operations may happen from software interrupt at
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.Dv IPL_SOFTCLOCK .
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.Sh FUNCTIONS
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.Bl -tag -width compact
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.It Fn pserialize_create
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Allocate a new synchronisation object.
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.It Fn pserialize_destroy
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Destroy the synchronisation object.
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No synchronisation activity should happen at this point.
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.It Fn pserialize_read_enter
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Enter the critical path of the reader side.
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Returns an IPL value, which must be passed to
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.Xr pserialize_read_exit 9 .
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Protected code path is not allowed to block.
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.It Fn pserialize_read_exit
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Exit the critical path of the reader side.
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Takes the IPL value returned by
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.Xr pserialize_read_enter 9 .
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.It Fn pserialize_perform
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Perform the passive serialization on the writer side.
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Passing of this function ensures that no readers are in action.
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Writers must be additionally serialized with a separate mechanism,
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e.g.
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.Xr mutex 9 .
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Operation blocks and it may only be performed from thread context.
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.El
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.\" -----
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.Sh EXAMPLES
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Typical code fragment in the writer side:
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.Bd -literal
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mutex_enter(\*[Am]writer_psz_lock);
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/*
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* Perform the updates (e.g. remove data items from a list).
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*/
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...
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pserialize_perform(object-\*[Gt]psz);
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/*
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* At this point it is safe to destroy old data items.
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*/
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mutex_exit(\*[Am]writer_psz_lock);
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.Ed
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.\" -----
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.Sh CODE REFERENCES
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The
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.Nm
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is implemented within the file
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.Pa sys/kern/subr_pserialize.c .
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.Sh SEE ALSO
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2011-08-07 16:29:24 +04:00
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.Xr membar_ops 3 ,
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2011-07-30 22:19:04 +04:00
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.Xr condvar 9 ,
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.Xr mutex 9 ,
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.Xr rwlock 9
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.Rs
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.%A Hennessy, et al.
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2011-08-02 14:17:35 +04:00
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.%T "Passive serialization in a multitasking environment"
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2011-07-30 22:19:04 +04:00
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.%I US Patent and Trademark Office
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2011-08-02 14:17:35 +04:00
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.%D February 28, 1989
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2011-07-30 22:19:04 +04:00
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.%N US Patent 4809168
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.Re
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.Sh HISTORY
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Passive serialization mechanism first appeared in
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.Nx 6.0 .
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