/*
* Copyright (c) 1995
* The Regents of the University of California. All rights reserved.
*
* Copyright (C) 1997
* John S. Dyson. 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
* $Id: kern_lock.c,v 1.24 1999/03/12 03:09:29 julian Exp $
*/
#include "opt_lint.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/systm.h>
/*
* Locking primitives implementation.
* Locks provide shared/exclusive sychronization.
*/
#ifdef SIMPLELOCK_DEBUG
#define COUNT(p, x) if (p) (p)->p_locks += (x)
#else
#define COUNT(p, x)
#endif
#define LOCK_WAIT_TIME 100
#define LOCK_SAMPLE_WAIT 7
#if defined(DIAGNOSTIC)
#define LOCK_INLINE
#else
#define LOCK_INLINE __inline
#endif
#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
LK_SHARE_NONZERO | LK_WAIT_NONZERO)
static int acquire(struct lock *lkp, int extflags, int wanted);
static int apause(struct lock *lkp, int flags);
static int acquiredrain(struct lock *lkp, int extflags) ;
static LOCK_INLINE void
sharelock(struct lock *lkp, int incr) {
lkp->lk_flags |= LK_SHARE_NONZERO;
lkp->lk_sharecount += incr;
}
static LOCK_INLINE void
shareunlock(struct lock *lkp, int decr) {
KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
if (lkp->lk_sharecount == decr) {
lkp->lk_flags &= ~LK_SHARE_NONZERO;
if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
wakeup(lkp);
}
lkp->lk_sharecount = 0;
} else {
lkp->lk_sharecount -= decr;
}
}
/*
* This is the waitloop optimization, and note for this to work
* simple_lock and simple_unlock should be subroutines to avoid
* optimization troubles.
*/
static int
apause(struct lock *lkp, int flags) {
int lock_wait;
lock_wait = LOCK_WAIT_TIME;
for (; lock_wait > 0; lock_wait--) {
int i;
if ((lkp->lk_flags & flags) == 0)
return 0;
simple_unlock(&lkp->lk_interlock);
for (i = LOCK_SAMPLE_WAIT; i > 0; i--) {
if ((lkp->lk_flags & flags) == 0) {
simple_lock(&lkp->lk_interlock);
if ((lkp->lk_flags & flags) == 0)
return 0;
break;
}
}
}
return 1;
}
static int
acquire(struct lock *lkp, int extflags, int wanted) {
int s, error;
if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
return EBUSY;
}
if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) {
error = apause(lkp, wanted);
if (error == 0)
return 0;
}
s = splhigh();
while ((lkp->lk_flags & wanted) != 0) {
lkp->lk_flags |= LK_WAIT_NONZERO;
lkp->lk_waitcount++;
simple_unlock(&lkp->lk_interlock);
error = tsleep(lkp, lkp->lk_prio, lkp->lk_wmesg, lkp->lk_timo);
simple_lock(&lkp->lk_interlock);
if (lkp->lk_waitcount == 1) {
lkp->lk_flags &= ~LK_WAIT_NONZERO;
lkp->lk_waitcount = 0;
} else {
lkp->lk_waitcount--;
}
if (error) {
splx(s);
return error;
}
if (extflags & LK_SLEEPFAIL) {
splx(s);
return ENOLCK;
}
}
splx(s);
return 0;
}
/*
* 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
#ifndef DEBUG_LOCKS
lockmgr(lkp, flags, interlkp, p)
#else
debuglockmgr(lkp, flags, interlkp, p, name, file, line)
#endif
struct lock *lkp;
u_int flags;
struct simplelock *interlkp;
struct proc *p;
#ifdef DEBUG_LOCKS
const char *name; /* Name of lock function */
const char *file; /* Name of file call is from */
int line; /* Line number in file */
#endif
{
int error;
pid_t pid;
int extflags;
error = 0;
if (p == NULL)
pid = LK_KERNPROC;
else
pid = p->p_pid;
simple_lock(&lkp->lk_interlock);
if (flags & LK_INTERLOCK)
simple_unlock(interlkp);
extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
switch (flags & LK_TYPE_MASK) {
case LK_SHARED:
/*
* If we are not the exclusive lock holder, we have to block
* while there is an exclusive lock holder or while an
* exclusive lock request or upgrade request is in progress.
*
* However, if P_DEADLKTREAT is set, we override exclusive
* lock requests or upgrade requests ( but not the exclusive
* lock itself ).
*/
if (lkp->lk_lockholder != pid) {
if (p && (p->p_flag & P_DEADLKTREAT)) {
error = acquire(
lkp,
extflags,
LK_HAVE_EXCL
);
} else {
error = acquire(
lkp,
extflags,
LK_HAVE_EXCL | LK_WANT_EXCL |
LK_WANT_UPGRADE
);
}
if (error)
break;
sharelock(lkp, 1);
COUNT(p, 1);
break;
}
/*
* We hold an exclusive lock, so downgrade it to shared.
* An alternative would be to fail with EDEADLK.
*/
sharelock(lkp, 1);
COUNT(p, 1);
/* fall into downgrade */
case LK_DOWNGRADE:
#if !defined(MAX_PERF)
if (lkp->lk_lockholder != pid || lkp->lk_exclusivecount == 0)
panic("lockmgr: not holding exclusive lock");
#endif
sharelock(lkp, lkp->lk_exclusivecount);
lkp->lk_exclusivecount = 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) {
shareunlock(lkp, 1);
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 !defined(MAX_PERF)
if ((lkp->lk_lockholder == pid) || (lkp->lk_sharecount <= 0))
panic("lockmgr: upgrade exclusive lock");
#endif
shareunlock(lkp, 1);
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;
error = acquire(lkp, extflags, LK_SHARE_NONZERO);
lkp->lk_flags &= ~LK_WANT_UPGRADE;
if (error)
break;
lkp->lk_flags |= LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
#if !defined(MAX_PERF)
if (lkp->lk_exclusivecount != 0)
panic("lockmgr: non-zero exclusive count");
#endif
lkp->lk_exclusivecount = 1;
#if defined(DEBUG_LOCKS)
lkp->lk_filename = file;
lkp->lk_lineno = line;
lkp->lk_lockername = name;
#endif
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_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
LK_WAIT_NONZERO)
wakeup((void *)lkp);
/* fall into exclusive request */
case LK_EXCLUSIVE:
if (lkp->lk_lockholder == pid && pid != LK_KERNPROC) {
/*
* Recursive lock.
*/
#if !defined(MAX_PERF)
if ((extflags & LK_CANRECURSE) == 0)
panic("lockmgr: locking against myself");
#endif
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 | LK_SHARE_NONZERO))) {
error = EBUSY;
break;
}
/*
* Try to acquire the want_exclusive flag.
*/
error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
if (error)
break;
lkp->lk_flags |= LK_WANT_EXCL;
/*
* Wait for shared locks and upgrades to finish.
*/
error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO);
lkp->lk_flags &= ~LK_WANT_EXCL;
if (error)
break;
lkp->lk_flags |= LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
#if !defined(MAX_PERF)
if (lkp->lk_exclusivecount != 0)
panic("lockmgr: non-zero exclusive count");
#endif
lkp->lk_exclusivecount = 1;
#if defined(DEBUG_LOCKS)
lkp->lk_filename = file;
lkp->lk_lineno = line;
lkp->lk_lockername = name;
#endif
COUNT(p, 1);
break;
case LK_RELEASE:
if (lkp->lk_exclusivecount != 0) {
#if !defined(MAX_PERF)
if (pid != lkp->lk_lockholder)
panic("lockmgr: pid %d, not %s %d unlocking",
pid, "exclusive lock holder",
lkp->lk_lockholder);
#endif
COUNT(p, -1);
if (lkp->lk_exclusivecount == 1) {
lkp->lk_flags &= ~LK_HAVE_EXCL;
lkp->lk_lockholder = LK_NOPROC;
lkp->lk_exclusivecount = 0;
} else {
lkp->lk_exclusivecount--;
}
} else if (lkp->lk_flags & LK_SHARE_NONZERO) {
shareunlock(lkp, 1);
COUNT(p, -1);
}
if (lkp->lk_flags & LK_WAIT_NONZERO)
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 !defined(MAX_PERF)
if (lkp->lk_lockholder == pid)
panic("lockmgr: draining against myself");
#endif
error = acquiredrain(lkp, extflags);
if (error)
break;
lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
lkp->lk_lockholder = pid;
lkp->lk_exclusivecount = 1;
#if defined(DEBUG_LOCKS)
lkp->lk_filename = file;
lkp->lk_lineno = line;
lkp->lk_lockername = name;
#endif
COUNT(p, 1);
break;
default:
#if !defined(MAX_PERF)
simple_unlock(&lkp->lk_interlock);
panic("lockmgr: unknown locktype request %d",
flags & LK_TYPE_MASK);
#endif
/* NOTREACHED */
}
if ((lkp->lk_flags & LK_WAITDRAIN) &&
(lkp->lk_flags & (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE |
LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
lkp->lk_flags &= ~LK_WAITDRAIN;
wakeup((void *)&lkp->lk_flags);
}
simple_unlock(&lkp->lk_interlock);
return (error);
}
static int
acquiredrain(struct lock *lkp, int extflags) {
int error;
if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
return EBUSY;
}
error = apause(lkp, LK_ALL);
if (error == 0)
return 0;
while (lkp->lk_flags & LK_ALL) {
lkp->lk_flags |= LK_WAITDRAIN;
simple_unlock(&lkp->lk_interlock);
error = tsleep(&lkp->lk_flags, lkp->lk_prio,
lkp->lk_wmesg, lkp->lk_timo);
simple_lock(&lkp->lk_interlock);
if (error)
return error;
if (extflags & LK_SLEEPFAIL) {
return ENOLCK;
}
}
return 0;
}
/*
* Initialize a lock; required before use.
*/
void
lockinit(lkp, prio, wmesg, timo, flags)
struct lock *lkp;
int prio;
char *wmesg;
int timo;
int flags;
{
simple_lock_init(&lkp->lk_interlock);
lkp->lk_flags = (flags & LK_EXTFLG_MASK);
lkp->lk_sharecount = 0;
lkp->lk_waitcount = 0;
lkp->lk_exclusivecount = 0;
lkp->lk_prio = prio;
lkp->lk_wmesg = wmesg;
lkp->lk_timo = timo;
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);
}
/*
* 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 */
