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lock.h
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lock.h
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/*
* Copyright (c) 1995
* The Regents of the University of California. All rights reserved.
*
* This code contains ideas from software contributed to Berkeley by
* Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
* System project at Carnegie-Mellon University.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* @(#)lock.h 8.12 (Berkeley) 5/19/95
* $Id: lock.h,v 1.13 1999/01/20 14:49:12 eivind Exp $
*/
#ifndef _LOCK_H_
#define _LOCK_H_
#include <machine/lock.h>
/*
* The general lock structure. Provides for multiple shared locks,
* upgrading from shared to exclusive, and sleeping until the lock
* can be gained. The simple locks are defined in <machine/param.h>.
*/
struct lock {
struct simplelock lk_interlock; /* lock on remaining fields */
u_int lk_flags; /* see below */
int lk_sharecount; /* # of accepted shared locks */
int lk_waitcount; /* # of processes sleeping for lock */
short lk_exclusivecount; /* # of recursive exclusive locks */
short lk_prio; /* priority at which to sleep */
char *lk_wmesg; /* resource sleeping (for tsleep) */
int lk_timo; /* maximum sleep time (for tsleep) */
pid_t lk_lockholder; /* pid of exclusive lock holder */
#ifdef DEBUG_LOCKS
const char *lk_filename;
const char *lk_lockername;
int lk_lineno;
#endif
};
/*
* Lock request types:
* LK_SHARED - get one of many possible shared locks. If a process
* holding an exclusive lock requests a shared lock, the exclusive
* lock(s) will be downgraded to shared locks.
* 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 process holding an exclusive lock may get additional exclusive
* locks if it explicitly sets the LK_CANRECURSE flag in the lock
* request, or if the LK_CANRECUSE flag was set when the lock was
* initialized.
* LK_UPGRADE - the process must hold a shared lock that it wants to
* have upgraded to an exclusive lock. Other processes may get
* exclusive access to the resource between the time that the upgrade
* is requested and the time that it is granted.
* LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
* have upgraded to an exclusive lock. If the request succeeds, no
* other processes 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 process has already requested
* an upgrade, the request will fail (see error returns below).
* LK_DOWNGRADE - the process must hold an exclusive lock that it wants
* to have downgraded to a shared lock. If the process holds multiple
* (recursive) exclusive locks, they will all be downgraded to shared
* locks.
* LK_RELEASE - release one instance of a lock.
* 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.
*
* These are flags that are passed to the lockmgr routine.
*/
#define LK_TYPE_MASK 0x0000000f /* type of lock sought */
#define LK_SHARED 0x00000001 /* shared lock */
#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
#define LK_RELEASE 0x00000006 /* release any type of lock */
#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
/*
* External lock flags.
*
* The first three flags may be set in lock_init to set their mode permanently,
* or passed in as arguments to the lock manager. The LK_REENABLE flag may be
* set only at the release of a lock obtained by drain.
*/
#define LK_EXTFLG_MASK 0x01000070 /* mask of external flags */
#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
#define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
#define LK_NOPAUSE 0x01000000 /* no spinloop */
/*
* Internal lock flags.
*
* These flags are used internally to the lock manager.
*/
#define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
#define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
#define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
#define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
#define LK_DRAINING 0x00004000 /* lock is being drained */
#define LK_DRAINED 0x00008000 /* lock has been decommissioned */
/*
* Control flags
*
* Non-persistent external flags.
*/
#define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after
getting lk_interlock */
#define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
#define LK_NOOBJ 0x00040000 /* vget: don't create object */
/*
* Internal state flags corresponding to lk_sharecount, and lk_waitcount
*/
#define LK_SHARE_NONZERO 0x00100000
#define LK_WAIT_NONZERO 0x00200000
/*
* Lock return status.
*
* Successfully obtained locks return 0. Locks will always succeed
* unless one of the following is true:
* LK_FORCEUPGRADE is requested and some other process has already
* requested a lock upgrade (returns EBUSY).
* LK_WAIT is set and a sleep would be required (returns EBUSY).
* LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
* PCATCH is set in lock priority and a signal arrives (returns
* either EINTR or ERESTART if system calls is to be restarted).
* Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
* A failed lock attempt always returns a non-zero error value. No lock
* is held after an error return (in particular, a failed LK_UPGRADE
* or LK_FORCEUPGRADE will have released its shared access lock).
*/
/*
* Indicator that no process holds exclusive lock
*/
#define LK_KERNPROC ((pid_t) -2)
#define LK_NOPROC ((pid_t) -1)
void dumplockinfo(struct lock *lkp);
struct proc;
void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
int flags));
#ifdef DEBUG_LOCKS
int debuglockmgr __P((struct lock *, u_int flags,
struct simplelock *, struct proc *p,
const char *,
const char *,
int));
#define lockmgr(lockp, flags, slockp, proc) \
debuglockmgr((lockp), (flags), (slockp), (proc), \
"lockmgr", __FILE__, __LINE__)
#else
int lockmgr __P((struct lock *, u_int flags,
struct simplelock *, struct proc *p));
#endif
void lockmgr_printinfo __P((struct lock *));
int lockstatus __P((struct lock *));
#ifdef SIMPLELOCK_DEBUG
void _simple_unlock __P((struct simplelock *alp, const char *, int));
#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
int _simple_lock_try __P((struct simplelock *alp, const char *, int));
#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
void _simple_lock __P((struct simplelock *alp, const char *, int));
#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
void simple_lock_init __P((struct simplelock *alp));
#else /* !SIMPLELOCK_DEBUG */
#if NCPUS == 1 /* no multiprocessor locking is necessary */
#define NULL_SIMPLELOCKS
#define simple_lock_init(alp)
#define simple_lock(alp)
#define simple_lock_try(alp) (1) /* always succeeds */
#define simple_unlock(alp)
#endif /* NCPUS == 1 */
#endif /* !SIMPLELOCK_DEBUG */
#endif /* !_LOCK_H_ */