436eef361c
Use this instead of DEBUG_LASTREQS to decide whether to log lock
requests.
MFS:
vinumlock: Catch a potential race condition where one process is
waiting for a lock, and between the time it is woken and
it retries the lock, another process gets it and places it
in the first entry in the table.
This problem has not been observed, but it's possible, and
it's easy enough to fix.
Submitted by: tegge
vinumunlock: Catch a real bug capable of hanging a system. When
releasing a lock, vinumunlock() called wakeup_one. This
caused wakeups to sometimes get lost. After due
consideration, we think that this is due to the fact that
you can't guarantee that some other process is also
waiting on the same address. This makes wakeup_one a
very dangerous function to use.
265 lines
8.0 KiB
C
265 lines
8.0 KiB
C
/*-
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* Copyright (c) 1997, 1998
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* Nan Yang Computer Services Limited. All rights reserved.
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*
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* Parts copyright (c) 1997, 1998 Cybernet Corporation, NetMAX project.
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*
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* Written by Greg Lehey
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*
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* This software is distributed under the so-called ``Berkeley
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* License'':
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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 Nan Yang Computer
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* Services Limited.
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* 4. Neither the name of the Company 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 ``as is'', and any express or implied
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* warranties, including, but not limited to, the implied warranties of
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* merchantability and fitness for a particular purpose are disclaimed.
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* In no event shall the company or contributors be liable for any
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* direct, indirect, incidental, special, exemplary, or consequential
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* damages (including, but not limited to, procurement of substitute
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* goods or services; loss of use, data, or profits; or business
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* interruption) however caused and on any theory of liability, whether
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* in contract, strict liability, or tort (including negligence or
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* otherwise) arising in any way out of the use of this software, even if
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* advised of the possibility of such damage.
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*
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* $Id: vinumlock.c,v 1.13 2000/05/02 23:25:02 grog Exp grog $
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* $FreeBSD$
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*/
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#include <dev/vinum/vinumhdr.h>
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#include <dev/vinum/request.h>
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/* Lock a drive, wait if it's in use */
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#if VINUMDEBUG
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int
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lockdrive(struct drive *drive, char *file, int line)
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#else
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int
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lockdrive(struct drive *drive)
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#endif
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{
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int error;
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/* XXX get rid of drive->flags |= VF_LOCKING; */
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if ((drive->flags & VF_LOCKED) /* it's locked */
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&&(drive->pid == curproc->p_pid)) { /* by us! */
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#ifdef VINUMDEBUG
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log(LOG_WARNING,
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"vinum lockdrive: already locking %s from %s:%d, called from %s:%d\n",
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drive->label.name,
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drive->lockfilename,
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drive->lockline,
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basename(file),
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line);
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#else
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log(LOG_WARNING,
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"vinum lockdrive: already locking %s\n",
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drive->label.name);
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#endif
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return 0;
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}
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while ((drive->flags & VF_LOCKED) != 0) {
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/*
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* There are problems sleeping on a unique identifier,
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* since the drive structure can move, and the unlock
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* function can be called after killing the drive.
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* Solve this by waiting on this function; the number
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* of conflicts is negligible.
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*/
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if ((error = tsleep(&lockdrive,
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PRIBIO,
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"vindrv",
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0)) != 0)
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return error;
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}
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drive->flags |= VF_LOCKED;
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drive->pid = curproc->p_pid; /* it's a panic error if curproc is null */
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#ifdef VINUMDEBUG
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bcopy(basename(file), drive->lockfilename, 15);
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drive->lockfilename[15] = '\0'; /* truncate if necessary */
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drive->lockline = line;
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#endif
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return 0;
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}
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/* Unlock a drive and let the next one at it */
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void
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unlockdrive(struct drive *drive)
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{
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drive->flags &= ~VF_LOCKED;
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/* we don't reset pid: it's of hysterical interest */
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wakeup(&lockdrive);
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}
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/* Lock a stripe of a plex, wait if it's in use */
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struct rangelock *
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lockrange(daddr_t stripe, struct buf *bp, struct plex *plex)
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{
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struct rangelock *lock;
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struct rangelock *pos; /* position of first free lock */
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int foundlocks; /* number of locks found */
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/*
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* We could get by without counting the number
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* of locks we find, but we have a linear search
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* through a table which in most cases will be
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* empty. It's faster to stop when we've found
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* all the locks that are there. This is also
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* the reason why we put pos at the beginning
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* instead of the end, though it requires an
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* extra test.
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*/
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pos = NULL;
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foundlocks = 0;
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/*
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* we can't use 0 as a valid address, so
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* increment all addresses by 1.
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*/
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stripe++;
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mtx_lock(&plex->lockmtx);
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/* Wait here if the table is full */
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while (plex->usedlocks == PLEX_LOCKS) /* all in use */
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msleep(&plex->usedlocks, &plex->lockmtx, PRIBIO, "vlock", 0);
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#ifdef DIAGNOSTIC
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if (plex->usedlocks >= PLEX_LOCKS)
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panic("lockrange: Too many locks in use");
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#endif
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lock = plex->lock; /* pointer in lock table */
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if (plex->usedlocks > 0) /* something locked, */
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/* Search the lock table for our stripe */
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for (; lock < &plex->lock[PLEX_LOCKS]
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&& foundlocks < plex->usedlocks;
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lock++) {
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if (lock->stripe) { /* in use */
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foundlocks++; /* found another one in use */
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if ((lock->stripe == stripe) /* it's our stripe */
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&&(lock->bp != bp)) { /* but not our request */
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#ifdef VINUMDEBUG
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if (debug & DEBUG_LOCKREQS) {
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struct rangelockinfo lockinfo;
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lockinfo.stripe = stripe;
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lockinfo.bp = bp;
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lockinfo.plexno = plex->plexno;
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logrq(loginfo_lockwait, (union rqinfou) &lockinfo, bp);
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}
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#endif
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plex->lockwaits++; /* waited one more time */
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msleep(lock, &plex->lockmtx, PRIBIO, "vrlock", 0);
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lock = &plex->lock[-1]; /* start again */
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foundlocks = 0;
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pos = NULL;
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}
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} else if (pos == NULL) /* still looking for somewhere? */
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pos = lock; /* a place to put this one */
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}
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/*
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* This untidy looking code ensures that we'll
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* always end up pointing to the first free lock
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* entry, thus minimizing the number of
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* iterations necessary.
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*/
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if (pos == NULL) /* didn't find one on the way, */
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pos = lock; /* use the one we're pointing to */
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/*
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* The address range is free, and we're pointing
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* to the first unused entry. Make it ours.
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*/
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pos->stripe = stripe;
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pos->bp = bp;
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plex->usedlocks++; /* one more lock */
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mtx_unlock(&plex->lockmtx);
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#ifdef VINUMDEBUG
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if (debug & DEBUG_LOCKREQS) {
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struct rangelockinfo lockinfo;
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lockinfo.stripe = stripe;
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lockinfo.bp = bp;
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lockinfo.plexno = plex->plexno;
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logrq(loginfo_lock, (union rqinfou) &lockinfo, bp);
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}
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#endif
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return pos;
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}
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/* Unlock a volume and let the next one at it */
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void
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unlockrange(int plexno, struct rangelock *lock)
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{
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struct plex *plex;
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plex = &PLEX[plexno];
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#ifdef DIAGNOSTIC
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if (lock < &plex->lock[0] || lock >= &plex->lock[PLEX_LOCKS])
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panic("vinum: rangelock %p on plex %d invalid, not between %p and %p",
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lock,
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plexno,
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&plex->lock[0],
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&plex->lock[PLEX_LOCKS]);
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#endif
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#ifdef VINUMDEBUG
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if (debug & DEBUG_LOCKREQS) {
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struct rangelockinfo lockinfo;
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lockinfo.stripe = lock->stripe;
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lockinfo.bp = lock->bp;
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lockinfo.plexno = plex->plexno;
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logrq(loginfo_lockwait, (union rqinfou) &lockinfo, lock->bp);
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}
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#endif
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lock->stripe = 0; /* no longer used */
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plex->usedlocks--; /* one less lock */
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if (plex->usedlocks == PLEX_LOCKS - 1) /* we were full, */
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wakeup(&plex->usedlocks); /* get a waiter if one's there */
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wakeup((void *) lock);
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}
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/* Get a lock for the global config, wait if it's not available */
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int
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lock_config(void)
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{
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int error;
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while ((vinum_conf.flags & VF_LOCKED) != 0) {
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vinum_conf.flags |= VF_LOCKING;
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if ((error = tsleep(&vinum_conf, PRIBIO, "vincfg", 0)) != 0)
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return error;
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}
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vinum_conf.flags |= VF_LOCKED;
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return 0;
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}
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/* Unlock and wake up any waiters */
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void
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unlock_config(void)
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{
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vinum_conf.flags &= ~VF_LOCKED;
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if ((vinum_conf.flags & VF_LOCKING) != 0) {
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vinum_conf.flags &= ~VF_LOCKING;
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wakeup(&vinum_conf);
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}
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}
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/* Local Variables: */
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/* fill-column: 50 */
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/* End: */
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