462a7add8e
that it operates on lockmgr and sx locks. This can be useful for tracking down vnode deadlocks in VFS for example. Note that this command is a bit more fragile than 'show lockchain' as we have to poke around at the wait channel of a thread to see if it points to either a struct lock or a condition variable inside of a struct sx. If td_wchan points to something unmapped, then this command will terminate early due to a fault, but no harm will be done.
211 lines
8.5 KiB
C
211 lines
8.5 KiB
C
/*-
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* Copyright (c) 1995
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* The Regents of the University of California. All rights reserved.
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*
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* This code contains ideas from software contributed to Berkeley by
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* Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
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* System project at Carnegie-Mellon University.
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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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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)lock.h 8.12 (Berkeley) 5/19/95
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* $FreeBSD$
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*/
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#ifndef _SYS_LOCKMGR_H_
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#define _SYS_LOCKMGR_H_
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#ifdef DEBUG_LOCKS
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#include <sys/stack.h> /* XXX */
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#endif
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struct mtx;
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/*
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* The general lock structure. Provides for multiple shared locks,
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* upgrading from shared to exclusive, and sleeping until the lock
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* can be gained.
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*/
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struct lock {
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struct mtx *lk_interlock; /* lock on remaining fields */
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u_int lk_flags; /* see below */
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int lk_sharecount; /* # of accepted shared locks */
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int lk_waitcount; /* # of processes sleeping for lock */
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short lk_exclusivecount; /* # of recursive exclusive locks */
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short lk_prio; /* priority at which to sleep */
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const char *lk_wmesg; /* resource sleeping (for tsleep) */
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int lk_timo; /* maximum sleep time (for tsleep) */
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struct thread *lk_lockholder; /* thread of exclusive lock holder */
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struct lock *lk_newlock; /* lock taking over this lock */
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#ifdef DEBUG_LOCKS
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struct stack lk_stack;
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#endif
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};
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/*
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* Lock request types:
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* LK_SHARED - get one of many possible shared locks. If a process
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* holding an exclusive lock requests a shared lock, the exclusive
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* lock(s) will be downgraded to shared locks.
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* LK_EXCLUSIVE - stop further shared locks, when they are cleared,
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* grant a pending upgrade if it exists, then grant an exclusive
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* lock. Only one exclusive lock may exist at a time, except that
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* a process holding an exclusive lock may get additional exclusive
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* locks if it explicitly sets the LK_CANRECURSE flag in the lock
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* request, or if the LK_CANRECUSE flag was set when the lock was
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* initialized.
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* LK_UPGRADE - the process must hold a shared lock that it wants to
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* have upgraded to an exclusive lock. Other processes may get
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* exclusive access to the resource between the time that the upgrade
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* is requested and the time that it is granted.
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* LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
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* have upgraded to an exclusive lock. If the request succeeds, no
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* other processes will have gotten exclusive access to the resource
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* between the time that the upgrade is requested and the time that
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* it is granted. However, if another process has already requested
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* an upgrade, the request will fail (see error returns below).
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* LK_DOWNGRADE - the process must hold an exclusive lock that it wants
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* to have downgraded to a shared lock. If the process holds multiple
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* (recursive) exclusive locks, they will all be downgraded to shared
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* locks.
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* LK_RELEASE - release one instance of a lock.
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* LK_DRAIN - wait for all activity on the lock to end, then mark it
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* decommissioned. This feature is used before freeing a lock that
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* is part of a piece of memory that is about to be freed.
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* LK_EXCLOTHER - return for lockstatus(). Used when another process
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* holds the lock exclusively.
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*
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* These are flags that are passed to the lockmgr routine.
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*/
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#define LK_TYPE_MASK 0x0000000f /* type of lock sought */
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#define LK_SHARED 0x00000001 /* shared lock */
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#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
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#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
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#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
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#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
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#define LK_RELEASE 0x00000006 /* release any type of lock */
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#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
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#define LK_EXCLOTHER 0x00000008 /* other process holds lock */
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/*
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* External lock flags.
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*
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* These may be set in lock_init to set their mode permanently,
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* or passed in as arguments to the lock manager.
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*/
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#define LK_EXTFLG_MASK 0x00000ff0 /* mask of external flags */
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#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
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#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
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#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
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#define LK_NOSHARE 0x00000080 /* Only allow exclusive locks */
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#define LK_TIMELOCK 0x00000100 /* use lk_timo, else no timeout */
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/*
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* Nonpersistent external flags.
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*/
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#define LK_RETRY 0x00001000 /* vn_lock: retry until locked */
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#define LK_INTERLOCK 0x00002000 /*
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* unlock passed mutex after getting
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* lk_interlock
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*/
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/*
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* Internal lock flags.
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*
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* These flags are used internally to the lock manager.
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*/
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#define LK_WANT_UPGRADE 0x00010000 /* waiting for share-to-excl upgrade */
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#define LK_WANT_EXCL 0x00020000 /* exclusive lock sought */
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#define LK_HAVE_EXCL 0x00040000 /* exclusive lock obtained */
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#define LK_WAITDRAIN 0x00080000 /* process waiting for lock to drain */
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#define LK_DRAINING 0x00100000 /* lock is being drained */
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#define LK_INTERNAL 0x00200000/* The internal lock is already held */
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/*
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* Internal state flags corresponding to lk_sharecount, and lk_waitcount
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*/
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#define LK_SHARE_NONZERO 0x01000000
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#define LK_WAIT_NONZERO 0x02000000
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/*
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* Lock return status.
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*
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* Successfully obtained locks return 0. Locks will always succeed
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* unless one of the following is true:
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* LK_FORCEUPGRADE is requested and some other process has already
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* requested a lock upgrade (returns EBUSY).
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* LK_WAIT is set and a sleep would be required (returns EBUSY).
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* LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
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* PCATCH is set in lock priority and a signal arrives (returns
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* either EINTR or ERESTART if system calls is to be restarted).
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* Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
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* A failed lock attempt always returns a non-zero error value. No lock
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* is held after an error return (in particular, a failed LK_UPGRADE
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* or LK_FORCEUPGRADE will have released its shared access lock).
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*/
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/*
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* Indicator that no process holds exclusive lock
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*/
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#define LK_KERNPROC ((struct thread *)-2)
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#define LK_NOPROC ((struct thread *) -1)
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#ifdef INVARIANTS
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#define LOCKMGR_ASSERT(lkp, what, p) do { \
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switch ((what)) { \
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case LK_SHARED: \
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if (lockstatus((lkp), (p)) == LK_SHARED) \
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break; \
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/* fall into exclusive */ \
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case LK_EXCLUSIVE: \
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if (lockstatus((lkp), (p)) != LK_EXCLUSIVE) \
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panic("lock %s %s not held at %s:%d", \
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(lkp)->lk_wmesg, #what, __FILE__, \
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__LINE__); \
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break; \
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default: \
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panic("unknown LOCKMGR_ASSERT at %s:%d", __FILE__, \
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__LINE__); \
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} \
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} while (0)
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#else /* INVARIANTS */
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#define LOCKMGR_ASSERT(lkp, p, what)
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#endif /* INVARIANTS */
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void dumplockinfo(struct lock *lkp);
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struct thread;
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void lockinit(struct lock *, int prio, const char *wmesg,
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int timo, int flags);
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void lockdestroy(struct lock *);
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int lockmgr(struct lock *, u_int flags,
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struct mtx *, struct thread *p);
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void transferlockers(struct lock *, struct lock *);
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void lockmgr_printinfo(struct lock *);
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int lockstatus(struct lock *, struct thread *);
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int lockcount(struct lock *);
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#ifdef DDB
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int lockmgr_chain(struct thread *td, struct thread **ownerp);
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#endif
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#endif /* !_SYS_LOCKMGR_H_ */
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