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NetBSD/sys/kern/kern_lock.c
chs fce05250f9 more cleanup: 
remove simplelockrecurse, lockpausetime and PAUSE():
none of these serve any purpose anymore.
in the LOCKDEBUG functions, expand the splhigh() region to
cover the entire function.  without this there can still be races.
1999-07-19 03:21:11 +00:00

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/* $NetBSD: kern_lock.c,v 1.18 1999/07/19 03:21:11 chs Exp $ */
/*
* Copyright (c) 1995
* The Regents of the University of California. All rights reserved.
*
* This code contains ideas from software contributed to Berkeley by
* Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
* System project at Carnegie-Mellon University.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)kern_lock.c 8.18 (Berkeley) 5/21/95
*/
#include "opt_lockdebug.h"
#include "opt_ddb.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/systm.h>
#include <machine/cpu.h>
/*
* Locking primitives implementation.
* Locks provide shared/exclusive sychronization.
*/
#if defined(LOCKDEBUG) || defined(DIAGNOSTIC)
#define COUNT(p, x) if (p) (p)->p_locks += (x)
#else
#define COUNT(p, x)
#endif
/*
* Acquire a resource.
*/
#define ACQUIRE(lkp, error, extflags, wanted) \
for (error = 0; wanted; ) { \
(lkp)->lk_waitcount++; \
simple_unlock(&(lkp)->lk_interlock); \
error = tsleep((void *)lkp, (lkp)->lk_prio, \
(lkp)->lk_wmesg, (lkp)->lk_timo); \
simple_lock(&(lkp)->lk_interlock); \
(lkp)->lk_waitcount--; \
if (error) \
break; \
if ((extflags) & LK_SLEEPFAIL) { \
error = ENOLCK; \
break; \
} \
}
/*
* Initialize a lock; required before use.
*/
void
lockinit(lkp, prio, wmesg, timo, flags)
struct lock *lkp;
int prio;
const char *wmesg;
int timo;
int flags;
{
memset(lkp, 0, sizeof(struct lock));
simple_lock_init(&lkp->lk_interlock);
lkp->lk_flags = flags & LK_EXTFLG_MASK;
lkp->lk_prio = prio;
lkp->lk_timo = timo;
lkp->lk_wmesg = wmesg;
lkp->lk_lockholder = LK_NOPROC;
}
/*
* Determine the status of a lock.
*/
int
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);
}
/*
* Set, change, or release a lock.
*
* Shared requests increment the shared count. Exclusive requests set the
* LK_WANT_EXCL flag (preventing further shared locks), and wait for already
* accepted shared locks and shared-to-exclusive upgrades to go away.
*/
int
lockmgr(lkp, flags, interlkp)
__volatile struct lock *lkp;
u_int flags;
struct simplelock *interlkp;
{
int error;
pid_t pid;
int extflags;
struct proc *p = curproc;
error = 0;
if (p)
pid = p->p_pid;
else
pid = LK_KERNPROC;
simple_lock(&lkp->lk_interlock);
if (flags & LK_INTERLOCK)
simple_unlock(interlkp);
extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
#ifdef DIAGNOSTIC
/*
* Once a lock has drained, the LK_DRAINING flag is set and an
* exclusive lock is returned. The only valid operation thereafter
* is a single release of that exclusive lock. This final release
* clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
* further requests of any sort will result in a panic. The bits
* selected for these two flags are chosen so that they will be set
* in memory that is freed (freed memory is filled with 0xdeadbeef).
* The final release is permitted to give a new lease on life to
* the lock by specifying LK_REENABLE.
*/
if (lkp->lk_flags & (LK_DRAINING|LK_DRAINED)) {
if (lkp->lk_flags & LK_DRAINED)
panic("lockmgr: using decommissioned lock");
if ((flags & LK_TYPE_MASK) != LK_RELEASE ||
lkp->lk_lockholder != pid)
panic("lockmgr: non-release on draining lock: %d\n",
flags & LK_TYPE_MASK);
lkp->lk_flags &= ~LK_DRAINING;
if ((flags & LK_REENABLE) == 0)
lkp->lk_flags |= LK_DRAINED;
}
#endif DIAGNOSTIC
switch (flags & LK_TYPE_MASK) {
case LK_SHARED:
if (lkp->lk_lockholder != pid) {
/*
* If just polling, check to see if we will block.
*/
if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE))) {
error = EBUSY;
break;
}
/*
* Wait for exclusive locks and upgrades to clear.
*/
ACQUIRE(lkp, error, extflags, lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE));
if (error)
break;
lkp->lk_sharecount++;
COUNT(p, 1);
break;
}
/*
* We hold an exclusive lock, so downgrade it to shared.
* An alternative would be to fail with EDEADLK.
*/
lkp->lk_sharecount++;
COUNT(p, 1);
/* fall into downgrade */
case LK_DOWNGRADE:
if (lkp->lk_lockholder != pid || lkp->lk_exclusivecount == 0)
panic("lockmgr: not holding exclusive lock");
lkp->lk_sharecount += lkp->lk_exclusivecount;
lkp->lk_exclusivecount = 0;
lkp->lk_recurselevel = 0;
lkp->lk_flags &= ~LK_HAVE_EXCL;
lkp->lk_lockholder = LK_NOPROC;
if (lkp->lk_waitcount)
wakeup((void *)lkp);
break;
case LK_EXCLUPGRADE:
/*
* If another process is ahead of us to get an upgrade,
* then we want to fail rather than have an intervening
* exclusive access.
*/
if (lkp->lk_flags & LK_WANT_UPGRADE) {
lkp->lk_sharecount--;
COUNT(p, -1);
error = EBUSY;
break;
}
/* fall into normal upgrade */
case LK_UPGRADE:
/*
* Upgrade a shared lock to an exclusive one. If another
* shared lock has already requested an upgrade to an
* exclusive lock, our shared lock is released and an
* exclusive lock is requested (which will be granted
* after the upgrade). If we return an error, the file
* will always be unlocked.
*/
if (lkp->lk_lockholder == pid || lkp->lk_sharecount <= 0)
panic("lockmgr: upgrade exclusive lock");
lkp->lk_sharecount--;
COUNT(p, -1);
/*
* If we are just polling, check to see if we will block.
*/
if ((extflags & LK_NOWAIT) &&
((lkp->lk_flags & LK_WANT_UPGRADE) ||
lkp->lk_sharecount > 1)) {
error = EBUSY;
break;
}
if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
/*
* We are first shared lock to request an upgrade, so
* request upgrade and wait for the shared count to
* drop to zero, then take exclusive lock.
*/
lkp->lk_flags |= LK_WANT_UPGRADE;
ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
lkp->lk_flags &= ~LK_WANT_UPGRADE;
if (error)
break;
lkp->lk_flags |= LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
if (lkp->lk_exclusivecount != 0)
panic("lockmgr: non-zero exclusive count");
lkp->lk_exclusivecount = 1;
if (extflags & LK_SETRECURSE)
lkp->lk_recurselevel = 1;
COUNT(p, 1);
break;
}
/*
* Someone else has requested upgrade. Release our shared
* lock, awaken upgrade requestor if we are the last shared
* lock, then request an exclusive lock.
*/
if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
wakeup((void *)lkp);
/* fall into exclusive request */
case LK_EXCLUSIVE:
if (lkp->lk_lockholder == pid && pid != LK_KERNPROC) {
/*
* Recursive lock.
*/
if ((extflags & LK_CANRECURSE) == 0 &&
lkp->lk_recurselevel == 0) {
if (extflags & LK_RECURSEFAIL) {
error = EDEADLK;
break;
} else
panic("lockmgr: locking against myself");
}
lkp->lk_exclusivecount++;
if (extflags & LK_SETRECURSE &&
lkp->lk_recurselevel == 0)
lkp->lk_recurselevel = lkp->lk_exclusivecount;
COUNT(p, 1);
break;
}
/*
* If we are just polling, check to see if we will sleep.
*/
if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
lkp->lk_sharecount != 0)) {
error = EBUSY;
break;
}
/*
* Try to acquire the want_exclusive flag.
*/
ACQUIRE(lkp, error, extflags, lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL));
if (error)
break;
lkp->lk_flags |= LK_WANT_EXCL;
/*
* Wait for shared locks and upgrades to finish.
*/
ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 ||
(lkp->lk_flags & LK_WANT_UPGRADE));
lkp->lk_flags &= ~LK_WANT_EXCL;
if (error)
break;
lkp->lk_flags |= LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
if (lkp->lk_exclusivecount != 0)
panic("lockmgr: non-zero exclusive count");
lkp->lk_exclusivecount = 1;
if (extflags & LK_SETRECURSE)
lkp->lk_recurselevel = 1;
COUNT(p, 1);
break;
case LK_RELEASE:
if (lkp->lk_exclusivecount != 0) {
if (pid != lkp->lk_lockholder)
panic("lockmgr: pid %d, not exclusive lock "
"holder %d unlocking", pid,
lkp->lk_lockholder);
if (lkp->lk_exclusivecount == lkp->lk_recurselevel)
lkp->lk_recurselevel = 0;
lkp->lk_exclusivecount--;
COUNT(p, -1);
if (lkp->lk_exclusivecount == 0) {
lkp->lk_flags &= ~LK_HAVE_EXCL;
lkp->lk_lockholder = LK_NOPROC;
}
} else if (lkp->lk_sharecount != 0) {
lkp->lk_sharecount--;
COUNT(p, -1);
}
if (lkp->lk_waitcount)
wakeup((void *)lkp);
break;
case LK_DRAIN:
/*
* Check that we do not already hold the lock, as it can
* never drain if we do. Unfortunately, we have no way to
* check for holding a shared lock, but at least we can
* check for an exclusive one.
*/
if (lkp->lk_lockholder == pid)
panic("lockmgr: draining against myself");
/*
* If we are just polling, check to see if we will sleep.
*/
if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0)) {
error = EBUSY;
break;
}
for (error = 0; ((lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0); ) {
lkp->lk_flags |= LK_WAITDRAIN;
simple_unlock(&lkp->lk_interlock);
if ((error = tsleep((void *)&lkp->lk_flags,
lkp->lk_prio, lkp->lk_wmesg, lkp->lk_timo)))
return (error);
if ((extflags) & LK_SLEEPFAIL)
return (ENOLCK);
simple_lock(&lkp->lk_interlock);
}
lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
lkp->lk_exclusivecount = 1;
/* XXX unlikely that we'd want this */
if (extflags & LK_SETRECURSE)
lkp->lk_recurselevel = 1;
COUNT(p, 1);
break;
default:
simple_unlock(&lkp->lk_interlock);
panic("lockmgr: unknown locktype request %d",
flags & LK_TYPE_MASK);
/* NOTREACHED */
}
if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) == 0 &&
lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
lkp->lk_flags &= ~LK_WAITDRAIN;
wakeup((void *)&lkp->lk_flags);
}
simple_unlock(&lkp->lk_interlock);
return (error);
}
/*
* Print out information about state of a lock. Used by VOP_PRINT
* routines to display ststus 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(LOCKDEBUG) && !defined(MULTIPROCESSOR)
LIST_HEAD(slocklist, simplelock) slockdebuglist;
int simple_lock_debugger = 0;
/*
* 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;
alp->lock_file = NULL;
alp->lock_line = 0;
alp->unlock_file = NULL;
alp->unlock_line = 0;
alp->lock_holder = 0;
}
void
_simple_lock(alp, id, l)
__volatile struct simplelock *alp;
const char *id;
int l;
{
int s;
s = splhigh();
if (alp->lock_data == 1) {
printf("simple_lock: lock held\n");
printf("currently at: %s:%d\n", id, l);
printf("last locked: %s:%d\n",
alp->lock_file, alp->lock_line);
printf("last unlocked: %s:%d\n",
alp->unlock_file, alp->unlock_line);
if (simple_lock_debugger) {
Debugger();
}
splx(s);
return;
}
LIST_INSERT_HEAD(&slockdebuglist, (struct simplelock *)alp, list);
alp->lock_data = 1;
alp->lock_file = id;
alp->lock_line = l;
if (curproc)
curproc->p_simple_locks++;
splx(s);
}
int
_simple_lock_try(alp, id, l)
__volatile struct simplelock *alp;
const char *id;
int l;
{
int s;
s = splhigh();
if (alp->lock_data != 0) {
printf("simple_lock_try: lock held\n");
printf("currently at: %s:%d\n", id, l);
printf("last locked: %s:%d\n",
alp->lock_file, alp->lock_line);
printf("last unlocked: %s:%d\n",
alp->unlock_file, alp->unlock_line);
if (simple_lock_debugger) {
Debugger();
}
splx(s);
return (0);
}
alp->lock_data = 1;
alp->lock_file = id;
alp->lock_line = l;
LIST_INSERT_HEAD(&slockdebuglist, (struct simplelock *)alp, list);
if (curproc)
curproc->p_simple_locks++;
splx(s);
return (1);
}
void
_simple_unlock(alp, id, l)
__volatile struct simplelock *alp;
const char *id;
int l;
{
int s;
s = splhigh();
if (alp->lock_data == 0) {
printf("simple_unlock: lock not held\n");
printf("currently at: %s:%d\n", id, l);
printf("last locked: %s:%d\n",
alp->lock_file, alp->lock_line);
printf("last unlocked: %s:%d\n",
alp->unlock_file, alp->unlock_line);
if (simple_lock_debugger) {
Debugger();
}
splx(s);
return;
}
LIST_REMOVE(alp, list);
alp->list.le_next = NULL;
alp->list.le_prev = NULL;
alp->lock_data = 0;
alp->unlock_file = id;
alp->unlock_line = l;
if (curproc)
curproc->p_simple_locks--;
splx(s);
}
void
simple_lock_dump()
{
struct simplelock *alp;
int s;
s = splhigh();
printf("all simple locks:\n");
for (alp = LIST_FIRST(&slockdebuglist);
alp != NULL;
alp = LIST_NEXT(alp, list)) {
printf("%p %s:%d\n", alp, alp->lock_file, alp->lock_line);
}
splx(s);
}
void
simple_lock_freecheck(start, end)
void *start, *end;
{
struct simplelock *alp;
int s;
s = splhigh();
for (alp = LIST_FIRST(&slockdebuglist);
alp != NULL;
alp = LIST_NEXT(alp, list)) {
if ((void *)alp >= start && (void *)alp < end) {
printf("freeing simple_lock %p %s:%d\n",
alp, alp->lock_file, alp->lock_line);
#ifdef DDB
Debugger();
#endif
}
}
splx(s);
}
#endif /* LOCKDEBUG && ! MULTIPROCESSOR */
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