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

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

1 files changed, 239 insertions, 97 deletions

diff --git a/share/man/man9/lock.9 b/share/man/man9/lock.9
index b48c6fe..c737a54 100644
--- a/share/man/man9/lock.9
+++ b/share/man/man9/lock.9
@@ -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
+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
+.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
-returns the number of shared lock holders on a lock.
-The function
-.Fn lockstatus
-determines the status of a lock.
+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
-The following values are defined:
+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 .