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540 lines
15 KiB
C
540 lines
15 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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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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* @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
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* $Id: kern_lock.c,v 1.5 1997/03/25 17:11:30 peter Exp $
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*/
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#include <sys/param.h>
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#include <sys/proc.h>
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#include <sys/lock.h>
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#include <sys/systm.h>
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/*
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* Locking primitives implementation.
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* Locks provide shared/exclusive sychronization.
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*/
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#ifdef SIMPLELOCK_DEBUG
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#define COUNT(p, x) if (p) (p)->p_locks += (x)
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#else
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#define COUNT(p, x)
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#endif
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#if NCPUS > 1
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/*
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* For multiprocessor system, try spin lock first.
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*
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* This should be inline expanded below, but we cannot have #if
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* inside a multiline define.
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*/
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int lock_wait_time = 100;
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#define PAUSE(lkp, wanted) \
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if (lock_wait_time > 0) { \
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int i; \
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\
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simple_unlock(&lkp->lk_interlock); \
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for (i = lock_wait_time; i > 0; i--) \
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if (!(wanted)) \
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break; \
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simple_lock(&lkp->lk_interlock); \
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} \
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if (!(wanted)) \
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break;
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#else /* NCPUS == 1 */
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/*
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* It is an error to spin on a uniprocessor as nothing will ever cause
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* the simple lock to clear while we are executing.
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*/
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#define PAUSE(lkp, wanted)
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#endif /* NCPUS == 1 */
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/*
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* Acquire a resource.
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*/
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#define ACQUIRE(lkp, error, extflags, wanted) \
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PAUSE(lkp, wanted); \
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for (error = 0; wanted; ) { \
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(lkp)->lk_waitcount++; \
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simple_unlock(&(lkp)->lk_interlock); \
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error = tsleep((void *)lkp, (lkp)->lk_prio, \
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(lkp)->lk_wmesg, (lkp)->lk_timo); \
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simple_lock(&(lkp)->lk_interlock); \
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(lkp)->lk_waitcount--; \
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if (error) \
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break; \
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if ((extflags) & LK_SLEEPFAIL) { \
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error = ENOLCK; \
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break; \
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} \
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}
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/*
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* Initialize a lock; required before use.
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*/
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void
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lockinit(lkp, prio, wmesg, timo, flags)
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struct lock *lkp;
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int prio;
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char *wmesg;
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int timo;
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int flags;
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{
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simple_lock_init(&lkp->lk_interlock);
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lkp->lk_flags = flags & LK_EXTFLG_MASK;
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lkp->lk_sharecount = 0;
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lkp->lk_waitcount = 0;
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lkp->lk_exclusivecount = 0;
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lkp->lk_prio = prio;
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lkp->lk_wmesg = wmesg;
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lkp->lk_timo = timo;
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lkp->lk_lockholder = LK_NOPROC;
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}
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/*
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* Determine the status of a lock.
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*/
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int
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lockstatus(lkp)
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struct lock *lkp;
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{
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int lock_type = 0;
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simple_lock(&lkp->lk_interlock);
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if (lkp->lk_exclusivecount != 0)
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lock_type = LK_EXCLUSIVE;
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else if (lkp->lk_sharecount != 0)
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lock_type = LK_SHARED;
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simple_unlock(&lkp->lk_interlock);
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return (lock_type);
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}
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/*
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* Set, change, or release a lock.
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*
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* Shared requests increment the shared count. Exclusive requests set the
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* LK_WANT_EXCL flag (preventing further shared locks), and wait for already
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* accepted shared locks and shared-to-exclusive upgrades to go away.
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*/
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int
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lockmgr(lkp, flags, interlkp, p)
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__volatile struct lock *lkp;
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u_int flags;
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struct simplelock *interlkp;
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struct proc *p;
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{
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int error;
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pid_t pid;
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int extflags;
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error = 0;
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if (p)
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pid = p->p_pid;
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else
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pid = LK_KERNPROC;
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simple_lock(&lkp->lk_interlock);
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if (flags & LK_INTERLOCK)
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simple_unlock(interlkp);
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extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
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#ifdef DIAGNOSTIC
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/*
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* Once a lock has drained, the LK_DRAINING flag is set and an
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* exclusive lock is returned. The only valid operation thereafter
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* is a single release of that exclusive lock. This final release
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* clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
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* further requests of any sort will result in a panic. The bits
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* selected for these two flags are chosen so that they will be set
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* in memory that is freed (freed memory is filled with 0xdeadbeef).
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* The final release is permitted to give a new lease on life to
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* the lock by specifying LK_REENABLE.
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*/
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if (lkp->lk_flags & (LK_DRAINING|LK_DRAINED)) {
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if (lkp->lk_flags & LK_DRAINED)
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panic("lockmgr: using decommissioned lock");
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if ((flags & LK_TYPE_MASK) != LK_RELEASE ||
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lkp->lk_lockholder != pid)
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panic("lockmgr: non-release on draining lock: %d\n",
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flags & LK_TYPE_MASK);
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lkp->lk_flags &= ~LK_DRAINING;
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if ((flags & LK_REENABLE) == 0)
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lkp->lk_flags |= LK_DRAINED;
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}
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#endif DIAGNOSTIC
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switch (flags & LK_TYPE_MASK) {
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case LK_SHARED:
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if (lkp->lk_lockholder != pid) {
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/*
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* If just polling, check to see if we will block.
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*/
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if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE))) {
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error = EBUSY;
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break;
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}
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/*
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* Wait for exclusive locks and upgrades to clear.
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*/
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ACQUIRE(lkp, error, extflags, lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE));
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if (error)
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break;
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lkp->lk_sharecount++;
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COUNT(p, 1);
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break;
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}
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/*
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* We hold an exclusive lock, so downgrade it to shared.
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* An alternative would be to fail with EDEADLK.
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*/
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lkp->lk_sharecount++;
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COUNT(p, 1);
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/* fall into downgrade */
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case LK_DOWNGRADE:
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if (lkp->lk_lockholder != pid || lkp->lk_exclusivecount == 0)
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panic("lockmgr: not holding exclusive lock");
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lkp->lk_sharecount += lkp->lk_exclusivecount;
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lkp->lk_exclusivecount = 0;
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lkp->lk_flags &= ~LK_HAVE_EXCL;
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lkp->lk_lockholder = LK_NOPROC;
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if (lkp->lk_waitcount)
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wakeup((void *)lkp);
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break;
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case LK_EXCLUPGRADE:
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/*
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* If another process is ahead of us to get an upgrade,
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* then we want to fail rather than have an intervening
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* exclusive access.
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*/
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if (lkp->lk_flags & LK_WANT_UPGRADE) {
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lkp->lk_sharecount--;
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COUNT(p, -1);
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error = EBUSY;
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break;
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}
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/* fall into normal upgrade */
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case LK_UPGRADE:
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/*
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* Upgrade a shared lock to an exclusive one. If another
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* shared lock has already requested an upgrade to an
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* exclusive lock, our shared lock is released and an
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* exclusive lock is requested (which will be granted
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* after the upgrade). If we return an error, the file
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* will always be unlocked.
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*/
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if (lkp->lk_lockholder == pid || lkp->lk_sharecount <= 0)
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panic("lockmgr: upgrade exclusive lock");
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lkp->lk_sharecount--;
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COUNT(p, -1);
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/*
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* If we are just polling, check to see if we will block.
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*/
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if ((extflags & LK_NOWAIT) &&
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((lkp->lk_flags & LK_WANT_UPGRADE) ||
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lkp->lk_sharecount > 1)) {
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error = EBUSY;
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break;
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}
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if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
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/*
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* We are first shared lock to request an upgrade, so
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* request upgrade and wait for the shared count to
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* drop to zero, then take exclusive lock.
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*/
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lkp->lk_flags |= LK_WANT_UPGRADE;
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ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
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lkp->lk_flags &= ~LK_WANT_UPGRADE;
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if (error)
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break;
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lkp->lk_flags |= LK_HAVE_EXCL;
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lkp->lk_lockholder = pid;
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if (lkp->lk_exclusivecount != 0)
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panic("lockmgr: non-zero exclusive count");
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lkp->lk_exclusivecount = 1;
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COUNT(p, 1);
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break;
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}
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/*
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* Someone else has requested upgrade. Release our shared
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* lock, awaken upgrade requestor if we are the last shared
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* lock, then request an exclusive lock.
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*/
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if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
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wakeup((void *)lkp);
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/* fall into exclusive request */
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case LK_EXCLUSIVE:
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if (lkp->lk_lockholder == pid && pid != LK_KERNPROC) {
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/*
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* Recursive lock.
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*/
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if ((extflags & LK_CANRECURSE) == 0)
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panic("lockmgr: locking against myself");
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lkp->lk_exclusivecount++;
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COUNT(p, 1);
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break;
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}
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/*
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* If we are just polling, check to see if we will sleep.
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*/
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if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
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lkp->lk_sharecount != 0)) {
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error = EBUSY;
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break;
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}
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/*
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* Try to acquire the want_exclusive flag.
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*/
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ACQUIRE(lkp, error, extflags, lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL));
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if (error)
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break;
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lkp->lk_flags |= LK_WANT_EXCL;
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/*
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* Wait for shared locks and upgrades to finish.
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*/
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ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 ||
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(lkp->lk_flags & LK_WANT_UPGRADE));
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lkp->lk_flags &= ~LK_WANT_EXCL;
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if (error)
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break;
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lkp->lk_flags |= LK_HAVE_EXCL;
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lkp->lk_lockholder = pid;
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if (lkp->lk_exclusivecount != 0)
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panic("lockmgr: non-zero exclusive count");
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lkp->lk_exclusivecount = 1;
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COUNT(p, 1);
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break;
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case LK_RELEASE:
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if (lkp->lk_exclusivecount != 0) {
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if (pid != lkp->lk_lockholder)
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panic("lockmgr: pid %d, not %s %d unlocking",
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pid, "exclusive lock holder",
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lkp->lk_lockholder);
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lkp->lk_exclusivecount--;
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COUNT(p, -1);
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if (lkp->lk_exclusivecount == 0) {
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lkp->lk_flags &= ~LK_HAVE_EXCL;
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lkp->lk_lockholder = LK_NOPROC;
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}
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} else if (lkp->lk_sharecount != 0) {
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lkp->lk_sharecount--;
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COUNT(p, -1);
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}
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if (lkp->lk_waitcount)
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wakeup((void *)lkp);
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break;
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case LK_DRAIN:
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/*
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* Check that we do not already hold the lock, as it can
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* never drain if we do. Unfortunately, we have no way to
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* check for holding a shared lock, but at least we can
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* check for an exclusive one.
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*/
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if (lkp->lk_lockholder == pid)
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panic("lockmgr: draining against myself");
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/*
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* If we are just polling, check to see if we will sleep.
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*/
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if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
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lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0)) {
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error = EBUSY;
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break;
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}
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PAUSE(lkp, ((lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
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lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0));
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for (error = 0; ((lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
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lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0); ) {
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lkp->lk_flags |= LK_WAITDRAIN;
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simple_unlock(&lkp->lk_interlock);
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if (error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
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lkp->lk_wmesg, lkp->lk_timo))
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return (error);
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if ((extflags) & LK_SLEEPFAIL)
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return (ENOLCK);
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simple_lock(&lkp->lk_interlock);
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}
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lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
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lkp->lk_lockholder = pid;
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lkp->lk_exclusivecount = 1;
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COUNT(p, 1);
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break;
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default:
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simple_unlock(&lkp->lk_interlock);
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panic("lockmgr: unknown locktype request %d",
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flags & LK_TYPE_MASK);
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/* NOTREACHED */
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}
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if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
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(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) == 0 &&
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lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
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lkp->lk_flags &= ~LK_WAITDRAIN;
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wakeup((void *)&lkp->lk_flags);
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}
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simple_unlock(&lkp->lk_interlock);
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return (error);
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}
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/*
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* Print out information about state of a lock. Used by VOP_PRINT
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* routines to display ststus about contained locks.
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*/
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void
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lockmgr_printinfo(lkp)
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struct lock *lkp;
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{
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if (lkp->lk_sharecount)
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printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
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lkp->lk_sharecount);
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else if (lkp->lk_flags & LK_HAVE_EXCL)
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printf(" lock type %s: EXCL (count %d) by pid %d",
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lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
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if (lkp->lk_waitcount > 0)
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printf(" with %d pending", lkp->lk_waitcount);
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}
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#if defined(SIMPLELOCK_DEBUG) && NCPUS == 1
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#include <sys/kernel.h>
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#include <sys/sysctl.h>
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static int lockpausetime = 0;
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SYSCTL_INT(_debug, OID_AUTO, lockpausetime, CTLFLAG_RW, &lockpausetime, 0, "");
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int simplelockrecurse;
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/*
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* Simple lock functions so that the debugger can see from whence
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* they are being called.
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*/
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void
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simple_lock_init(alp)
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struct simplelock *alp;
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{
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alp->lock_data = 0;
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}
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void
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_simple_lock(alp, id, l)
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__volatile struct simplelock *alp;
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const char *id;
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int l;
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{
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if (simplelockrecurse)
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return;
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if (alp->lock_data == 1) {
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if (lockpausetime == -1)
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panic("%s:%d: simple_lock: lock held", id, l);
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printf("%s:%d: simple_lock: lock held\n", id, l);
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if (lockpausetime == 1) {
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Debugger("simple_lock");
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/*BACKTRACE(curproc); */
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} else if (lockpausetime > 1) {
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printf("%s:%d: simple_lock: lock held...", id, l);
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tsleep(&lockpausetime, PCATCH | PPAUSE, "slock",
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lockpausetime * hz);
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printf(" continuing\n");
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}
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}
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alp->lock_data = 1;
|
|
if (curproc)
|
|
curproc->p_simple_locks++;
|
|
}
|
|
|
|
int
|
|
_simple_lock_try(alp, id, l)
|
|
__volatile struct simplelock *alp;
|
|
const char *id;
|
|
int l;
|
|
{
|
|
|
|
if (alp->lock_data)
|
|
return (0);
|
|
if (simplelockrecurse)
|
|
return (1);
|
|
alp->lock_data = 1;
|
|
if (curproc)
|
|
curproc->p_simple_locks++;
|
|
return (1);
|
|
}
|
|
|
|
void
|
|
_simple_unlock(alp, id, l)
|
|
__volatile struct simplelock *alp;
|
|
const char *id;
|
|
int l;
|
|
{
|
|
|
|
if (simplelockrecurse)
|
|
return;
|
|
if (alp->lock_data == 0) {
|
|
if (lockpausetime == -1)
|
|
panic("%s:%d: simple_unlock: lock not held", id, l);
|
|
printf("%s:%d: simple_unlock: lock not held\n", id, l);
|
|
if (lockpausetime == 1) {
|
|
Debugger("simple_unlock");
|
|
/* BACKTRACE(curproc); */
|
|
} else if (lockpausetime > 1) {
|
|
printf("%s:%d: simple_unlock: lock not held...", id, l);
|
|
tsleep(&lockpausetime, PCATCH | PPAUSE, "sunlock",
|
|
lockpausetime * hz);
|
|
printf(" continuing\n");
|
|
}
|
|
}
|
|
alp->lock_data = 0;
|
|
if (curproc)
|
|
curproc->p_simple_locks--;
|
|
}
|
|
#endif /* SIMPLELOCK_DEBUG && NCPUS == 1 */
|