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Diffstat (limited to 'sys/vm/lock.h')
| -rw-r--r-- | sys/vm/lock.h | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/sys/vm/lock.h b/sys/vm/lock.h new file mode 100644 index 000000000000..6adf53be6ded --- /dev/null +++ b/sys/vm/lock.h @@ -0,0 +1,180 @@ +/* + * 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 + */ + +#ifndef _LOCK_H_ +#define _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 */ +}; +/* + * 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 0x00000070 /* 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 */ +/* + * 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 */ + +/* + * 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) + +struct proc; + +void lockinit __P((struct lock *, int prio, char *wmesg, int timo, + int flags)); +int lockmgr __P((__volatile struct lock *, u_int flags, + struct simplelock *, struct proc *p)); +int lockstatus __P((struct lock *)); + +#ifdef DEBUG +void _simple_unlock __P((__volatile struct simplelock *alp, const char *, int)); +#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__) +int _simple_lock_try __P((__volatile struct simplelock *alp, const char *, int)); +#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__) +void _simple_lock __P((__volatile struct simplelock *alp, const char *, int)); +#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__) +void simple_lock_init __P((struct simplelock *alp)); +#else /* !DEBUG */ +#if NCPUS == 1 /* no multiprocessor locking is necessary */ +#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 /* !DEBUG */ + +#endif /* !_LOCK_H_ */ |