2 .\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice(s), this list of conditions and the following disclaimer as
9 .\" the first lines of this file unmodified other than the possible
10 .\" addition of one or more copyright notices.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice(s), this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
15 .\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
16 .\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17 .\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
18 .\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
19 .\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
20 .\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
21 .\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
22 .\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
27 .\" $FreeBSD: src/share/man/man9/lock.9,v 1.11 2003/09/08 19:57:21 ru Exp $
28 .\" $DragonFly: src/share/man/man9/lock.9,v 1.2 2004/05/10 13:06:53 hmp Exp $
39 .Nd "lockmgr family of functions"
44 .Fn lockinit "struct lock *lkp" "int prio" "char *wmesg" "int timo" "int flags"
46 .Fn lockcount "struct lock *lkp"
48 .Fn lockmgr "struct lock *lkp" "u_int flags" "lwkt_tokref_t interlkp" "struct thread *td"
50 .Fn lockstatus "struct lock *lkp" "struct thread *td"
52 .Fn lockmgr_printinfo "struct lock *lkp"
56 function is used to initialize a lock.
57 It must be called before any operation can be performed on a lock.
59 .Bl -tag -width ".Fa wmesg"
61 A pointer to the lock to initialize.
63 The priority passed to
67 This is used for both debugging output and
70 The timeout value passed to
73 The flags the lock is to be initialized with.
74 .Bl -tag -width ".Dv LG_CANRECURSE"
76 Do not sleep while acquiring the lock.
80 Allow recursive exclusive locks.
82 Re-enable the lock after a drain.
84 Disable the spinlock while acquiring the lock.
88 during a sleep; otherwise, 0 is used.
94 function returns a count of the number of exclusive locks and shared locks
100 function handles general locking functionality within the kernel, including
101 support for shared and exclusive locks, and recursion.
103 is also able to upgrade and downgrade locks.
106 .Bl -tag -width ".Fa interlkp"
108 A pointer to the lock to manipulate.
110 Flags indicating what action is to be taken.
111 .Bl -tag -width ".Dv LK_EXCLUPGRADE"
113 Acquire a shared lock.
114 If an exclusive lock is currently held, it will be downgraded.
116 Acquire an exclusive lock.
117 If an exclusive lock is already held, and
119 is not set, the system will
122 Downgrade exclusive lock to a shared lock.
123 Downgrading a shared lock is not permitted.
124 If an exclusive lock has been recursed, all references will be downgraded.
125 .It Dv LK_EXCLUPGRADE
126 Upgrade a shared lock to an exclusive lock.
129 if there is someone ahead of you in line waiting for an upgrade.
130 If this call fails, the shared lock is lost.
131 Attempts to upgrade an exclusive lock will cause a
134 Upgrade a shared lock to an exclusive lock.
135 If this call fails, the shared lock is lost.
136 Attempts to upgrade an exclusive lock will cause a
140 Releasing a lock that is not held can cause a
143 Wait for all activity on the lock to end, then mark it decommissioned.
144 This is used before freeing a lock that is part of a piece of memory that is
151 Fail if operation has slept.
153 Do not allow the call to sleep.
154 This can be used to test the lock.
156 Allow recursion on an exclusive lock.
157 For every lock there must be a release.
159 Unlock the interlock (which should be locked already).
162 An interlock mutex for controlling group access to the lock.
169 is currently owned and not recursed, and will return it unlocked.
173 A thread responsible for this call.
181 function returns the status of the lock in relation to the
188 and an exclusive lock is held,
193 .Fn lockmgr_printinfo
194 function prints debugging information about the lock.
195 It is used primarily by
201 function returns an integer greater than or equal to zero.
205 function returns 0 on success and non-zero on failure.
210 .Bl -tag -width ".Dv LK_EXCLUSIVE"
212 An exclusive lock is held by the thread
215 An exclusive lock is held by someone other than the thread
218 A shared lock is held.
220 The lock is not held by anyone.
228 was set, and a sleep would have been required.
236 was set in the lock priority, and a signal was delivered during a sleep.
242 was set in the lock priority, a signal was delivered during a sleep,
243 and the system call is to be restarted.
244 .It Bq Er EWOULDBLOCK
245 a non-zero timeout was given, and the timeout expired.
256 must be held prior to calling
258 and will be returned unlocked.
260 Upgrade attempts that fail result in the loss of the lock that
262 Also, it is invalid to upgrade an
263 exclusive lock, and a
265 will be the result of trying.
271 This man page was written by
272 .An Chad David Aq davidc@acns.ab.ca .