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Code Issues Releases Activity

Merged all of the lockmgr functions into a single file (lock.9); as well,

Browse Source 
some content and layout changes were made.

lock.9 had existed before but was never added to Makefile, so it was
never installed.  That is why the duplicate files were created in the
first place.

Reviewed by:	ru, alfred
This commit is contained in:
Chad David 2002-01-26 00:09:41 +00:00
parent ab09ef008f
commit 5385e8bfab
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=89806
7 changed files with 245 additions and 513 deletions
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7
share/man/man9/Makefile
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@ -45,8 +45,7 @@ MAN= BUF_LOCK.9 BUF_LOCKFREE.9 BUF_LOCKINIT.9 BUF_REFCNT.9 \
groupmember.9 \
ifnet.9 inittodr.9 intro.9 ithread.9 \
kernacc.9 kobj.9 kthread.9 ktr.9 \
lockcount.9 lockdestroy.9 lockmgr.9 lockmgr_printinfo.9 \
lockstatus.9 \
lock.9 \
make_dev.9 malloc.9 mbchain.9 mbuf.9 mdchain.9 \
mi_switch.9 microseq.9 microtime.9 microuptime.9 \
module.9 mutex.9 \
@ -251,6 +250,10 @@ MLINKS+=bus_generic_read_ivar.9 bus_generic_write_ivar.9
MLINKS+=ucred.9 crget.9 ucred.9 crhold.9 ucred.9 crfree.9
MLINKS+=ucred.9 crshared.9 ucred.9 crcopy.9 ucred.9 crdup.9
MLINKS+= lock.9 lockinit.9 lock.9 lockdestroy.9
MLINKS+= lock.9 lockcount.9 lock.9 lockmgr.9
MLINKS+= lock.9 lockstatus.9 lock.9 lockmgr_printinfo.9
MLINKS+=mbchain.9 mb_init.9
MLINKS+=mbchain.9 mb_initm.9
MLINKS+=mbchain.9 mb_done.9

338
share/man/man9/lock.9
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@ -1,139 +1,281 @@
.\" Copyright (c) 2000
.\" The Regents of the University of California. All rights reserved.
.\"
.\" All rights reserved.
.\" Copyright (C) 2002 Chad David <davidc@acns.ab.ca>. 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.
.\" notice(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" notice(s), 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 DEVELOPERS ``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 DEVELOPERS 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.
.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd October 24, 2000
.Dd July 9, 2001
.Dt LOCK 9
.Os
.Sh NAME
.Nm lockinit ,
.Nm lockmgr ,
.Nm lockdestroy ,
.Nm lockcount ,
.Nm lockstatus
.Nd kernel thread locking
.Nm lockmgr ,
.Nm lockstatus ,
.Nm lockmgr_printinfo
.Nd "lockmgr family of functions"
.Sh SYNOPSIS
.In sys/types.h
.In sys/lock.h
.In sys/lockmgr.h
.Ft void
.Fn lockinit "struct lock *lkp" "int prio" "char *wmesg" "int timo" "int flags"
.Ft int
.Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *interlkp" "struct thread *td"
.Ft void
.Fn lockdestroy "struct lock *lkp"
.Ft int
.Fn lockcount "struct lock *lkp"
.Ft int
.Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *interlkp" "struct thread *td"
.Ft int
.Fn lockstatus "struct lock *lkp" "struct thread *td"
.Ft void
.Fn lockmgr_printinfo "struct lock *lkp"
.Sh DESCRIPTION
The function
The
.Fn lockinit
is used to initialise a lock.
It is required if locks are used.
The function
.Fn lockmgr
is used to manage locks.
The function
.Fn lockcount
returns the number of shared lock holders on a lock.
The function
.Fn lockstatus
determines the status of a lock.
function is used to initialize a lock.
It must be called prior to any operation could be performed on a lock.
Its arguments are:
.Bl -tag -width ".Fa wmesg"
.It Fa lkp
A pointer to the lock to initialize.
.It Fa prio
The priority passed to
.Xr msleep 9 .
.It Fa wmesg
The lock message.
This is used for both debugging output and
.Xr msleep 9 .
.It Fa timo
The timeout value passed to
.Xr msleep 9 .
.It Fa flags
The flags the lock is to be initialized with.
.Bl -tag -width ".Dv LG_CANRECURSE"
.It Dv LK_NOWAIT
Do not sleep while acquiring the lock.
.It Dv LK_SLEEPFAIL
Fail after a sleep.
.It Dv LK_CANRECURSE
Allow recursive exclusive locks.
.It Dv LK_REENABLE
Re-enable the lock after a drain.
.It Dv LK_NOPAUSE
Disable the spinlock while acquiring the lock.
.It Dv LK_TIMELOCK
Use
.Fa timo
during a sleep; otherwise, 0 is used.
.El
.El
.Pp
The following values are defined:
The
.Fn lockdestroy
function is used to destroy a lock, and while it is called in a number of
places in the kernel, it currently does nothing.
.Pp
The
.Fn lockcount
function returns a count of the number of exclusive locks and shared locks
held against the lock
.Fa lkp .
.Pp
The
.Fn lockmgr
function handles general locking functionality within the kernel, including
support for shared and exclusive locks, and recursion.
.Fn lockmgr
is also able to upgrade and downgrade locks.
.Pp
Its arguments are:
.Bl -tag -width ".Fa interlkp"
.It Fa lkp
A pointer to the lock to manipulate.
.It Fa flags
Flags indicating what action is to be taken.
.Bl -tag -width ".Dv LK_EXCLUPGRADE"
.It Dv LK_SHARED
get one of many possible shared locks.
If a thread holding an exclusive lock requests a shared lock,
the exclusive lock(s) will be downgraded to shared locks.
Acquire a shared lock.
If an exclusive lock is currently held, it will be downgraded.
.It Dv LK_EXCLUSIVE
stop further shared locks, when they are cleared,
grant a pending upgrade if it exists, then grant an exclusive
lock.
Only one exclusive lock may exist at a time, except that
a thread holding an exclusive lock may get additional exclusive
locks if it explicitly sets the
Acquire an exclusive lock.
If an exclusive lock is already held, and
.Dv LK_CANRECURSE
flag in the lock request, or if the
.Dv LK_CANRECURSE
flag was set when the lock was initialized.
.It Dv LK_UPGRADE
the thread must hold a shared lock that it wants to
have upgraded to an exclusive lock.
Other threads may get exclusive access to the resource between
the time that the upgrade is requested and the time that it is
granted.
.It Dv LK_EXCLUPGRADE
the thread must hold a shared lock that it wants to
have upgraded to an exclusive lock.
If the request succeeds, no other thread will have gotten
exclusive access to the resource between the time that the upgrade
is requested and the time that it is granted.
However, if another thread has already requested an upgrade,
the request will fail.
is not set, the system will
.Xr panic 9 .
.It Dv LK_DOWNGRADE
the thread must hold an exclusive lock that it wants
to have downgraded to a shared lock.
If the thread holds multiple (recursive) exclusive locks,
they will all be downgraded to shared locks.
Downgrade exclusive lock to a shared lock.
Downgrading a shared lock is not permitted.
If an exclusive lock has been recursed, all references will be downgraded.
.It Dv LK_EXCLUPGRADE
Upgrade a shared lock to an exclusive lock.
Fails with
.Er EBUSY
if there is someone ahead of use waiting for an upgrade.
If this call fails, the shared lock is lost.
Attempt to upgrade an exclusive lock will cause a
.Xr panic 9 .
.It Dv LK_UPGRADE
Upgrade a shared lock to an exclusive lock.
If this call fails, the shared lock is lost.
Attempt to upgrade an exclusive lock will cause a
.Xr panic 9 .
.It Dv LK_RELEASE
release one instance of a lock.
Release the lock.
Releasing a lock that is not held can cause a
.Xr panic 9 .
.It Dv LK_DRAIN
wait for all activity on the lock to end, then mark it
decommissioned.
This feature is used before freeing a lock that is part of a
piece of memory that is about to be freed.
.It Dv LK_EXCLOTHER
return for
.Fn lockstatus .
Used when another thread holds the lock exclusively.
Wait for all activity on the lock to end, then mark it decommissioned.
This is used before freeing a lock that is part of a piece of memory that is
about to be freed.
(As documented in
.Aq Pa sys/lockmgr.h . )
.It Dv LK_SLEEPFAIL
Fail if operation has slept.
.It Dv LK_NOWAIT
Do not allow the call to sleep.
This can be used to test the lock.
.It Dv LK_CANRECURSE
Allow recursion on an exclusive lock.
For every lock there must be a release.
.It Dv LK_INTERLOCK
Unlock the interlock (which should be locked already).
.El
.It Fa interlkp
An interlock mutex for controlling group access to the lock.
If
.Dv LK_INTERLOCK
is specified,
.Fn lockmgr
assumes
.Fa interlkp
is currently owned and not recursed, and will return it unlocked.
See
.Xr mtx_assert 9 .
.It Fa td
A thread responsible for this call.
.Dv NULL
becomes
.Dv LK_KERNPROC .
.El
.Pp
The
.Fn lockstatus
function returns the status of the lock in relation to the
.Vt thread
passed to it.
Note that if
.Fa td
is
.Dv NULL
and an exclusive lock is held,
.Dv LK_EXCLUSIVE
will be returned.
.Pp
The
.Fn lockmgr_printinfo
function prints debugging information about the lock.
It is used primarily by
.Xr VOP_PRINT 9
functions.
.Sh RETURN VALUES
Successfully obtained locks return 0.
Locks will always succeed unless one of the following is true:
The
.Fn lockcount
function returns an integer greater than or equal to zero.
.Pp
The
.Fn lockmgr
function returns 0 on success and non-zero on failure.
.Pp
The
.Fn lockstatus
function returns:
.Bl -tag -width ".Dv LK_EXCLUSIVE"
.It Dv LK_EXCLUSIVE
An exclusive lock is held by the thread
.Fa td .
.It Dv LK_EXCLOTHER
An exclusive lock is held by someone other than the thread
.Fa td .
.It Dv LK_SHARED
A shared lock is held.
.It Li 0
The lock is not held by anyone.
.El
.Sh ERRORS
.Fn lockmgr
fails if:
.Bl -tag -width Er
.It Bq Er EBUSY
.Dv LK_FORCEUPGRADE
is requested and some other thread has already
requested a lock upgrade; returns
.Er EBUSY .
.Dv LK_WAIT
is set and a sleep would be required; returns
.Er EBUSY .
was requested and another thread had already requested a lock upgrade.
.It Bq Er EBUSY
.Dv LK_NOWAIT
was set, and a sleep would have been required.
.It Bq Er ENOLCK
.Dv LK_SLEEPFAIL
is set and a sleep was done; returns
.Er ENOLCK .
was set and
.Fn lockmgr
did sleep.
.It Bq Er EINTR
.Dv PCATCH
is set in lock priority and a signal arrives; returns
either
.Er EINTR
or
was set in the lock priority, and a signal was delivered during a sleep.
Note the
.Er ERESTART
if system calls is to be restarted.
Non-null lock timeout and timeout expires; returns
.Er EWOULDBLOCK .
A failed lock attempt always returns a non-zero error value.
No lock is held after an error return (in particular, a failed
.Dv LK_UPGRADE
or
.Dv LK_FORCEUPGRADE
will have released its shared
access lock).
error below.
.It Bq Er ERESTART
.Dv PCATCH
was set in the lock priority, a signal was delivered during a sleep,
and the system call is to be restarted.
.It Bq Er EWOULDBLOCK
a non-zero timeout was given, and the timeout expired.
.El
.Sh LOCKS
If
.Dv LK_INTERLOCK
is passed in the
.Fa flags
argument to
.Fn lockmgr ,
the
.Fa interlkp
must be held prior to calling
.Fn lockmgr ,
and will be returned unlocked.
.Pp
Upgrade attempts that fail result in the loss of the lock that
is currently held.
Also, it is invalid to upgrade an
exclusive lock, and a
.Xr panic 9
will be the result of trying.
.Sh SEE ALSO
.Xr msleep 9 ,
.Xr mtx_assert 9 ,
.Xr panic 9 ,
.Xr VOP_PRINT 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

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@ -1,61 +0,0 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd July 9, 2001
.Dt LOCKCOUNT 9
.Os
.Sh NAME
.Nm lockcount
.Nd "returns the reference count of a lock"
.Sh SYNOPSIS
.In sys/types.h
.In sys/lockmgr.h
.Ft int
.Fn lockcount "struct lock *lkp"
.Sh DESCRIPTION
The
.Fn lockcount
function returns the reference count of the lock.
The reference
count is the sum of exclusive locks and shared locks.
.Pp
Its arguments are:
.Bl -tag -width ".Fa lkp"
.It Fa lkp
The lock to return the reference count on.
.El
.Sh RETURN VALUES
An integer greater than or equal to zero.
.Sh SEE ALSO
.Xr lockdestroy 9 ,
.Xr lockmgr 9 ,
.Xr lockmgr_printinfo 9 ,
.Xr lockstatus 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

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@ -1,58 +0,0 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd July 9, 2001
.Dt LOCKDESTROY 9
.Os
.Sh NAME
.Nm lockdestroy
.Nd "destroys a lock"
.Sh SYNOPSIS
.In sys/param.h
.In sys/lockmgr.h
.Ft void
.Fn lockdestroy "struct lock *lkp"
.Sh DESCRIPTION
The
.Fn lockdestroy
function destroys the given lock.
(Currently is does nothing!)
.Pp
Its argument is:
.Bl -tag -width ".Fa lkp"
.It Fa lkp
The lock to destroy.
.El
.Sh SEE ALSO
.Xr lockcount 9 ,
.Xr lockmgr 9 ,
.Xr lockmgr_printinfo 9 ,
.Xr lockstatus 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

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@ -1,151 +0,0 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd July 9, 2001
.Dt LOCKMGR 9
.Os
.Sh NAME
.Nm lockmgr
.Nd "acquires, releases and updates locks"
.Sh SYNOPSIS
.In sys/types.h
.In sys/lockmgr.h
.Ft int
.Fn lockmgr "struct lock *lkp" "u_int flags" "struct mtx *interlkp" "struct thread *td"
.Sh DESCRIPTION
The
.Fn lockmgr
function handles general locking functionality within the kernel, including
support for shared and exclusive locks, and recursion.
Locks can also be upgraded and downgraded.
.Pp
Its arguments are:
.Bl -tag -width ".Fa interlkp"
.It Fa lkp
A pointer to the lock to manipulate.
.It Fa flags
Flags indicating what action is to be taken.
.Bl -tag -width ".Dv LK_EXCLUPGRADE"
.It Dv LK_SHARED
Acquire a shared lock.
If we currently hold an exclusive lock it will be downgraded.
.It Dv LK_EXCLUSIVE
Acquire an exclusive lock.
If we already hold an exclusive lock and
.Dv LK_CANRECURSE
is not set we will panic.
.It Dv LK_DOWNGRADE
Downgrade our exclusive lock to a shared lock.
Downgrading a shared lock is not valid.
If the exclusive lock has been recursed, all references will be downgraded.
.It Dv LK_EXCLUPGRADE
Upgrade our lock to an exclusive lock.
Will fail with
.Er EBUSY
if there is someone ahead of use waiting for an upgrade.
If this call fails we loose our shared lock.
Upgrading an exclusive lock will cause a panic.
.It Dv LK_UPGRADE
Upgrades our lock to an exclusive lock.
If this call fails we loose
our shared lock.
Upgrading an exclusive lock will cause a panic.
.It Dv LK_RELEASE
Release the lock.
Releasing a lock that you do not hold can cause a panic.
.It Dv LK_DRAIN
Waits for all activity on the lock to end, and then marks it decommissioned.
This is used before freeing a lock that is part of a piece of memory that is
about to be freed.
(As documented in
.Pa sys/lockmgr.h . )
.It Dv LK_SLEEPFAIL
If we had to sleep for the lock then fail.
.It Dv LK_NOWAIT
Do not allow the call to sleep.
This can be used to test the lock.
.It Dv LK_CANRECURSE
It is ok to recurse on an exclusive lock.
For every lock there must be a release.
.It Dv LK_INTERLOCK
Unlock the interlock, which is of course locked already.
.El
.It Fa interlkp
An interlock mutex for controlling group access to the lock.
If
.Dv LK_INTERLOCK
is specified,
.Fn lockmgr
assumes
.Fa interlkp
is currently owned and not recursed, and will return it unlocked.
See
.Xr mtx_assert 9 .
.It Fa td
The thread responsible for this call.
.Dv NULL
becomes
.Dv LK_KERNPROC .
.El
.Sh LOCKS
If
.Dv LK_INTERLOCK
is specified then
.Fa interlkp
must be held prior to calling
.Fn lockmgr
and will be returned unlocked.
.Pp
Upgrade attempts that fail result in the loss of the lock that
is currently held.
As well, it is not valid to upgrade an
exclusive lock, and a panic will be the result of trying.
.Sh RETURN VALUES
A value of 0 is returned on success.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EBUSY
Either
.Dv LK_NOWAIT
was specified and
.Fn lockmgr
would have slept, or another thread was ahead of you in line for an exclusive
upgrade.
.It Bq Er ENOLCK
.Dv LK_SLEEP_FAIL
was set and we slept.
.El
.Sh SEE ALSO
.Xr lockcount 9 ,
.Xr lockdestroy 9 ,
.Xr lockmgr_printinfo 9 ,
.Xr lockstatus 9 ,
.Xr mutex 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

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@ -1,60 +0,0 @@
.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. 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(s), this list of conditions and the following disclaimer as
.\" the first lines of this file unmodified other than the possible
.\" addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.\" $FreeBSD$
.\"
.Dd July 9, 2001
.Dt LOCKMGR_PRINTINFO 9
.Os
.Sh NAME
.Nm lockmgr_printinfo
.Nd "prints information about the lock"
.Sh SYNOPSIS
.In sys/types.h
.In sys/lockmgr.h
.Ft void
.Fn lockmgr_printinfo "struct lock *lkp"
.Sh DESCRIPTION
The
.Fn lockmgr_printinfo
function prints information about the lock including the lock
time and the wait count.
.Pp
Its argument is:
.Bl -tag -width ".Fa lkp"
.It Fa lkp
The lock to print.
.El
.Sh NOTES
This function seems to only exist for debugging purposes.
.Sh SEE ALSO
.Xr lockcount 9 ,
.Xr lockdestroy 9 ,
.Xr lockmgr 9 ,
.Xr lockstatus 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .

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.\"
.\" Copyright (C) 2001 Chad David <davidc@acns.ab.ca>. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
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.\" $FreeBSD$
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.Dd July 9, 2001
.Dt LOCKSTATUS 9
.Os
.Sh NAME
.Nm lockstatus
.Nd "returns the lock status"
.Sh SYNOPSIS
.In sys/types.h
.In sys/lockmgr.h
.Ft int
.Fn lockstatus "struct lock *lkp" "struct thread *td"
.Sh DESCRIPTION
The
.Fn lockstatus
function returns the status of the lock in relation to the
.Vt thread
passed to it.
.Pp
Its arguments are:
.Bl -tag -width ".Fa lkp"
.It Fa lkp
The lock to return the status of.
.It Fa td
The thread to check any exclusive locks against.
If
.Fa td
is
.Dv NULL
and an exclusive lock is held,
.Dv LK_EXCLUSIVE
is returned.
.El
.Sh RETURN VALUES
.Bl -tag -width ".Dv LK_EXCLUSIVE"
.It Dv LK_EXCLUSIVE
An exclusive lock is held by the thread
.Fa td
passed in.
.It Dv LK_EXCLOTHER
An exclusive lock is held by someone other then the thread
.Fa td
passed in.
.It Dv LK_SHARED
A shared lock is held.
.It 0
The lock is not held by anyone.
.El
.Sh SEE ALSO
.Xr lockcount 9 ,
.Xr lockdestroy 9 ,
.Xr lockmgr 9 ,
.Xr lockmgr_printinfo 9
.Sh AUTHORS
This man page was written by
.An Chad David Aq davidc@acns.ab.ca .