540 lines
15 KiB
C
540 lines
15 KiB
C
/*
|
|
* 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
|
|
* $Id: kern_lock.c,v 1.5 1997/03/25 17:11:30 peter Exp $
|
|
*/
|
|
|
|
#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
|
|
|
|
#if NCPUS > 1
|
|
|
|
/*
|
|
* For multiprocessor system, try spin lock first.
|
|
*
|
|
* This should be inline expanded below, but we cannot have #if
|
|
* inside a multiline define.
|
|
*/
|
|
int lock_wait_time = 100;
|
|
#define PAUSE(lkp, wanted) \
|
|
if (lock_wait_time > 0) { \
|
|
int i; \
|
|
\
|
|
simple_unlock(&lkp->lk_interlock); \
|
|
for (i = lock_wait_time; i > 0; i--) \
|
|
if (!(wanted)) \
|
|
break; \
|
|
simple_lock(&lkp->lk_interlock); \
|
|
} \
|
|
if (!(wanted)) \
|
|
break;
|
|
|
|
#else /* NCPUS == 1 */
|
|
|
|
/*
|
|
* It is an error to spin on a uniprocessor as nothing will ever cause
|
|
* the simple lock to clear while we are executing.
|
|
*/
|
|
#define PAUSE(lkp, wanted)
|
|
|
|
#endif /* NCPUS == 1 */
|
|
|
|
/*
|
|
* Acquire a resource.
|
|
*/
|
|
#define ACQUIRE(lkp, error, extflags, wanted) \
|
|
PAUSE(lkp, 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;
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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, p)
|
|
__volatile struct lock *lkp;
|
|
u_int flags;
|
|
struct simplelock *interlkp;
|
|
struct proc *p;
|
|
{
|
|
int error;
|
|
pid_t pid;
|
|
int extflags;
|
|
|
|
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_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;
|
|
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)
|
|
panic("lockmgr: locking against myself");
|
|
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;
|
|
COUNT(p, 1);
|
|
break;
|
|
|
|
case LK_RELEASE:
|
|
if (lkp->lk_exclusivecount != 0) {
|
|
if (pid != lkp->lk_lockholder)
|
|
panic("lockmgr: pid %d, not %s %d unlocking",
|
|
pid, "exclusive lock holder",
|
|
lkp->lk_lockholder);
|
|
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;
|
|
}
|
|
PAUSE(lkp, ((lkp->lk_flags &
|
|
(LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
|
|
lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0));
|
|
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;
|
|
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(SIMPLELOCK_DEBUG) && NCPUS == 1
|
|
#include <sys/kernel.h>
|
|
#include <sys/sysctl.h>
|
|
|
|
static int lockpausetime = 0;
|
|
SYSCTL_INT(_debug, OID_AUTO, lockpausetime, CTLFLAG_RW, &lockpausetime, 0, "");
|
|
|
|
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)
|
|
__volatile 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)
|
|
__volatile struct simplelock *alp;
|
|
const char *id;
|
|
int l;
|
|
{
|
|
|
|
if (alp->lock_data)
|
|
return (0);
|
|
if (simplelockrecurse)
|
|
return (1);
|
|
alp->lock_data = 1;
|
|
if (curproc)
|
|
curproc->p_simple_locks++;
|
|
return (1);
|
|
}
|
|
|
|
void
|
|
_simple_unlock(alp, id, l)
|
|
__volatile struct simplelock *alp;
|
|
const char *id;
|
|
int l;
|
|
{
|
|
|
|
if (simplelockrecurse)
|
|
return;
|
|
if (alp->lock_data == 0) {
|
|
if (lockpausetime == -1)
|
|
panic("%s:%d: simple_unlock: lock not held", id, l);
|
|
printf("%s:%d: simple_unlock: lock not held\n", id, l);
|
|
if (lockpausetime == 1) {
|
|
Debugger("simple_unlock");
|
|
/* BACKTRACE(curproc); */
|
|
} else if (lockpausetime > 1) {
|
|
printf("%s:%d: simple_unlock: lock not held...", id, l);
|
|
tsleep(&lockpausetime, PCATCH | PPAUSE, "sunlock",
|
|
lockpausetime * hz);
|
|
printf(" continuing\n");
|
|
}
|
|
}
|
|
alp->lock_data = 0;
|
|
if (curproc)
|
|
curproc->p_simple_locks--;
|
|
}
|
|
#endif /* SIMPLELOCK_DEBUG && NCPUS == 1 */
|