33638e9384
if LK_RECURSIVE is not set, as we will simply return that the lock is busy and not actually deadlock. This allows processes to use polling locks against buffers that they may already hold exclusively locked.
653 lines
16 KiB
C
653 lines
16 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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* Copyright (C) 1997
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* John S. Dyson. 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 1.26 1999/06/26 02:46:00 mckusick Exp $
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*/
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#include "opt_lint.h"
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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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#define LOCK_WAIT_TIME 100
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#define LOCK_SAMPLE_WAIT 7
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#if defined(DIAGNOSTIC)
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#define LOCK_INLINE
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#else
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#define LOCK_INLINE __inline
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#endif
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#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
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LK_SHARE_NONZERO | LK_WAIT_NONZERO)
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static int acquire(struct lock *lkp, int extflags, int wanted);
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static int apause(struct lock *lkp, int flags);
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static int acquiredrain(struct lock *lkp, int extflags) ;
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static LOCK_INLINE void
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sharelock(struct lock *lkp, int incr) {
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lkp->lk_flags |= LK_SHARE_NONZERO;
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lkp->lk_sharecount += incr;
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}
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static LOCK_INLINE void
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shareunlock(struct lock *lkp, int decr) {
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KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
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if (lkp->lk_sharecount == decr) {
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lkp->lk_flags &= ~LK_SHARE_NONZERO;
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if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
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wakeup(lkp);
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}
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lkp->lk_sharecount = 0;
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} else {
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lkp->lk_sharecount -= decr;
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}
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}
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/*
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* This is the waitloop optimization, and note for this to work
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* simple_lock and simple_unlock should be subroutines to avoid
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* optimization troubles.
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*/
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static int
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apause(struct lock *lkp, int flags) {
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int lock_wait;
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lock_wait = LOCK_WAIT_TIME;
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for (; lock_wait > 0; lock_wait--) {
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int i;
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if ((lkp->lk_flags & flags) == 0)
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return 0;
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simple_unlock(&lkp->lk_interlock);
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for (i = LOCK_SAMPLE_WAIT; i > 0; i--) {
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if ((lkp->lk_flags & flags) == 0) {
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simple_lock(&lkp->lk_interlock);
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if ((lkp->lk_flags & flags) == 0)
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return 0;
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break;
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}
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}
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}
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return 1;
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}
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static int
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acquire(struct lock *lkp, int extflags, int wanted) {
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int s, error;
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if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
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return EBUSY;
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}
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if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) {
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error = apause(lkp, wanted);
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if (error == 0)
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return 0;
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}
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s = splhigh();
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while ((lkp->lk_flags & wanted) != 0) {
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lkp->lk_flags |= LK_WAIT_NONZERO;
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lkp->lk_waitcount++;
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simple_unlock(&lkp->lk_interlock);
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error = tsleep(lkp, lkp->lk_prio, lkp->lk_wmesg, lkp->lk_timo);
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simple_lock(&lkp->lk_interlock);
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if (lkp->lk_waitcount == 1) {
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lkp->lk_flags &= ~LK_WAIT_NONZERO;
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lkp->lk_waitcount = 0;
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} else {
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lkp->lk_waitcount--;
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}
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if (error) {
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splx(s);
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return error;
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}
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if (extflags & LK_SLEEPFAIL) {
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splx(s);
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return ENOLCK;
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}
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}
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splx(s);
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return 0;
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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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#ifndef DEBUG_LOCKS
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lockmgr(lkp, flags, interlkp, p)
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#else
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debuglockmgr(lkp, flags, interlkp, p, name, file, line)
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#endif
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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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#ifdef DEBUG_LOCKS
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const char *name; /* Name of lock function */
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const char *file; /* Name of file call is from */
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int line; /* Line number in file */
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#endif
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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 == NULL)
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pid = LK_KERNPROC;
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else
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pid = p->p_pid;
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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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switch (flags & LK_TYPE_MASK) {
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case LK_SHARED:
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/*
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* If we are not the exclusive lock holder, we have to block
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* while there is an exclusive lock holder or while an
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* exclusive lock request or upgrade request is in progress.
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*
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* However, if P_DEADLKTREAT is set, we override exclusive
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* lock requests or upgrade requests ( but not the exclusive
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* lock itself ).
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*/
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if (lkp->lk_lockholder != pid) {
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if (p && (p->p_flag & P_DEADLKTREAT)) {
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error = acquire(
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lkp,
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extflags,
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LK_HAVE_EXCL
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);
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} else {
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error = acquire(
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lkp,
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extflags,
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LK_HAVE_EXCL | LK_WANT_EXCL |
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LK_WANT_UPGRADE
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);
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}
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if (error)
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break;
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sharelock(lkp, 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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* 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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sharelock(lkp, 1);
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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 !defined(MAX_PERF)
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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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#endif
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sharelock(lkp, 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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shareunlock(lkp, 1);
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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 !defined(MAX_PERF)
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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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#endif
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shareunlock(lkp, 1);
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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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error = acquire(lkp, extflags, LK_SHARE_NONZERO);
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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 !defined(MAX_PERF)
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if (lkp->lk_exclusivecount != 0)
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panic("lockmgr: non-zero exclusive count");
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#endif
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lkp->lk_exclusivecount = 1;
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#if defined(DEBUG_LOCKS)
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lkp->lk_filename = file;
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lkp->lk_lineno = line;
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lkp->lk_lockername = name;
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#endif
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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_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
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LK_WAIT_NONZERO)
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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 !defined(MAX_PERF)
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if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
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panic("lockmgr: locking against myself");
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#endif
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if ((extflags & LK_CANRECURSE) != 0) {
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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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/*
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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) &&
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(lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO))) {
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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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error = acquire(lkp, extflags, (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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error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO);
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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 !defined(MAX_PERF)
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if (lkp->lk_exclusivecount != 0)
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panic("lockmgr: non-zero exclusive count");
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#endif
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lkp->lk_exclusivecount = 1;
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#if defined(DEBUG_LOCKS)
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lkp->lk_filename = file;
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lkp->lk_lineno = line;
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lkp->lk_lockername = name;
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#endif
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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 !defined(MAX_PERF)
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if (lkp->lk_lockholder != pid &&
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lkp->lk_lockholder != LK_KERNPROC)
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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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#endif
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COUNT(p, -1);
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if (lkp->lk_exclusivecount == 1) {
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lkp->lk_flags &= ~LK_HAVE_EXCL;
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lkp->lk_lockholder = LK_NOPROC;
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lkp->lk_exclusivecount = 0;
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} else {
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lkp->lk_exclusivecount--;
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}
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} else if (lkp->lk_flags & LK_SHARE_NONZERO) {
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shareunlock(lkp, 1);
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COUNT(p, -1);
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}
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if (lkp->lk_flags & LK_WAIT_NONZERO)
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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 !defined(MAX_PERF)
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if (lkp->lk_lockholder == pid)
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panic("lockmgr: draining against myself");
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#endif
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error = acquiredrain(lkp, extflags);
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if (error)
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break;
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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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#if defined(DEBUG_LOCKS)
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lkp->lk_filename = file;
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lkp->lk_lineno = line;
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lkp->lk_lockername = name;
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#endif
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COUNT(p, 1);
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break;
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default:
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#if !defined(MAX_PERF)
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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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#endif
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/* NOTREACHED */
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}
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if ((lkp->lk_flags & LK_WAITDRAIN) &&
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(lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
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LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 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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static int
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acquiredrain(struct lock *lkp, int extflags) {
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int error;
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|
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if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
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return EBUSY;
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}
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error = apause(lkp, LK_ALL);
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if (error == 0)
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return 0;
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while (lkp->lk_flags & LK_ALL) {
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lkp->lk_flags |= LK_WAITDRAIN;
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simple_unlock(&lkp->lk_interlock);
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error = tsleep(&lkp->lk_flags, 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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if (error)
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return error;
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if (extflags & LK_SLEEPFAIL) {
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return ENOLCK;
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}
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}
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return 0;
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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)
|
|
struct lock *lkp;
|
|
{
|
|
int lock_type = 0;
|
|
|
|
simple_lock(&lkp->lk_interlock);
|
|
if (lkp->lk_exclusivecount != 0)
|
|
lock_type = LK_EXCLUSIVE;
|
|
else if (lkp->lk_sharecount != 0)
|
|
lock_type = LK_SHARED;
|
|
simple_unlock(&lkp->lk_interlock);
|
|
return (lock_type);
|
|
}
|
|
|
|
/*
|
|
* Determine the number of holders of a lock.
|
|
*/
|
|
int
|
|
lockcount(lkp)
|
|
struct lock *lkp;
|
|
{
|
|
int count;
|
|
|
|
simple_lock(&lkp->lk_interlock);
|
|
count = lkp->lk_exclusivecount + lkp->lk_sharecount;
|
|
simple_unlock(&lkp->lk_interlock);
|
|
return (count);
|
|
}
|
|
|
|
/*
|
|
* Print out information about state of a lock. Used by VOP_PRINT
|
|
* routines to display status about contained locks.
|
|
*/
|
|
void
|
|
lockmgr_printinfo(lkp)
|
|
struct lock *lkp;
|
|
{
|
|
|
|
if (lkp->lk_sharecount)
|
|
printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
|
|
lkp->lk_sharecount);
|
|
else if (lkp->lk_flags & LK_HAVE_EXCL)
|
|
printf(" lock type %s: EXCL (count %d) by pid %d",
|
|
lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
|
|
if (lkp->lk_waitcount > 0)
|
|
printf(" with %d pending", lkp->lk_waitcount);
|
|
}
|
|
|
|
#if defined(SIMPLELOCK_DEBUG) && (NCPUS == 1 || defined(COMPILING_LINT))
|
|
#include <sys/kernel.h>
|
|
#include <sys/sysctl.h>
|
|
|
|
static int lockpausetime = 0;
|
|
SYSCTL_INT(_debug, OID_AUTO, lockpausetime, CTLFLAG_RW, &lockpausetime, 0, "");
|
|
|
|
static int simplelockrecurse;
|
|
|
|
/*
|
|
* Simple lock functions so that the debugger can see from whence
|
|
* they are being called.
|
|
*/
|
|
void
|
|
simple_lock_init(alp)
|
|
struct simplelock *alp;
|
|
{
|
|
|
|
alp->lock_data = 0;
|
|
}
|
|
|
|
void
|
|
_simple_lock(alp, id, l)
|
|
struct simplelock *alp;
|
|
const char *id;
|
|
int l;
|
|
{
|
|
|
|
if (simplelockrecurse)
|
|
return;
|
|
if (alp->lock_data == 1) {
|
|
if (lockpausetime == -1)
|
|
panic("%s:%d: simple_lock: lock held", id, l);
|
|
printf("%s:%d: simple_lock: lock held\n", id, l);
|
|
if (lockpausetime == 1) {
|
|
Debugger("simple_lock");
|
|
/*BACKTRACE(curproc); */
|
|
} else if (lockpausetime > 1) {
|
|
printf("%s:%d: simple_lock: lock held...", id, l);
|
|
tsleep(&lockpausetime, PCATCH | PPAUSE, "slock",
|
|
lockpausetime * hz);
|
|
printf(" continuing\n");
|
|
}
|
|
}
|
|
alp->lock_data = 1;
|
|
if (curproc)
|
|
curproc->p_simple_locks++;
|
|
}
|
|
|
|
int
|
|
_simple_lock_try(alp, id, l)
|
|
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)
|
|
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--;
|
|
}
|
|
#elif defined(SIMPLELOCK_DEBUG)
|
|
#error "SIMPLELOCK_DEBUG is not compatible with SMP!"
|
|
#endif /* SIMPLELOCK_DEBUG && NCPUS == 1 */
|