witness.4 revision 1.3
$OpenBSD: witness.4,v 1.3 2017/04/22 11:12:04 visa Exp $
Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
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 AUTHOR 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 AUTHOR 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)
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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.
$FreeBSD: head/share/man/man4/witness.4 301719 2016-06-09 06:55:00Z trasz $
.Dd $Mdocdate: April 22 2017 $ .Dt WITNESS 4 .Os .Sh NAME .Nm witness .Nd lock validation facility .Sh DESCRIPTION The .Nm module keeps track of the locks acquired and released by each thread. It also keeps track of the order in which locks are acquired with respect to each other. Each time a lock is acquired, .Nm uses these two lists to verify that a lock is not being acquired in the wrong order. If a lock order violation is detected, then a message is printed to the kernel console detailing the locks involved and the locations in question.
Copyright (c) 2001 John H. Baldwin <jhb@FreeBSD.org>
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 AUTHOR 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 AUTHOR 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.
$FreeBSD: head/share/man/man4/witness.4 301719 2016-06-09 06:55:00Z trasz $
.Dd $Mdocdate: April 22 2017 $ .Dt WITNESS 4 .Os .Sh NAME .Nm witness .Nd lock validation facility .Sh DESCRIPTION The .Nm module keeps track of the locks acquired and released by each thread. It also keeps track of the order in which locks are acquired with respect to each other. Each time a lock is acquired, .Nm uses these two lists to verify that a lock is not being acquired in the wrong order. If a lock order violation is detected, then a message is printed to the kernel console detailing the locks involved and the locations in question.
p The .Nm code also checks various other conditions such as verifying that one does not recurse on a non-recursive lock, or attempt an upgrade on a shared lock held by another thread. If any of these checks fail, then the kernel will panic. .Sh SEE ALSO .Xr ddb 4 , .Xr options 4 , .Xr mutex 9 , .Xr rwlock 9 .Sh HISTORY The .Nm code first appeared in sx 5.0 and was imported from there into .Fx 5.0 . The .Ox port was derived from .Fx and first appeared in .Ox 6.2 .