Import 4.4BSD-Lite2 onto CSRG branch
This commit is contained in:
parent
2179734791
commit
53bf4bb2cf
sys
531
sys/kern/kern_lock.c
Normal file
531
sys/kern/kern_lock.c
Normal file
@ -0,0 +1,531 @@
|
||||
/*
|
||||
* 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 <sys/param.h>
|
||||
#include <sys/proc.h>
|
||||
#include <sys/lock.h>
|
||||
#include <machine/cpu.h>
|
||||
|
||||
/*
|
||||
* Locking primitives implementation.
|
||||
* Locks provide shared/exclusive sychronization.
|
||||
*/
|
||||
|
||||
#ifdef 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;
|
||||
{
|
||||
|
||||
bzero(lkp, 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, 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.
|
||||
*/
|
||||
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(DEBUG) && NCPUS == 1
|
||||
#include <sys/kernel.h>
|
||||
#include <vm/vm.h>
|
||||
#include <sys/sysctl.h>
|
||||
int lockpausetime = 0;
|
||||
struct ctldebug debug2 = { "lockpausetime", &lockpausetime };
|
||||
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) {
|
||||
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) {
|
||||
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 /* DEBUG && NCPUS == 1 */
|
180
sys/sys/lock.h
Normal file
180
sys/sys/lock.h
Normal file
@ -0,0 +1,180 @@
|
||||
/*
|
||||
* 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.
|
||||
*
|
||||
* @(#)lock.h 8.12 (Berkeley) 5/19/95
|
||||
*/
|
||||
|
||||
#ifndef _LOCK_H_
|
||||
#define _LOCK_H_
|
||||
|
||||
/*
|
||||
* The general lock structure. Provides for multiple shared locks,
|
||||
* upgrading from shared to exclusive, and sleeping until the lock
|
||||
* can be gained. The simple locks are defined in <machine/param.h>.
|
||||
*/
|
||||
struct lock {
|
||||
struct simplelock lk_interlock; /* lock on remaining fields */
|
||||
u_int lk_flags; /* see below */
|
||||
int lk_sharecount; /* # of accepted shared locks */
|
||||
int lk_waitcount; /* # of processes sleeping for lock */
|
||||
short lk_exclusivecount; /* # of recursive exclusive locks */
|
||||
short lk_prio; /* priority at which to sleep */
|
||||
char *lk_wmesg; /* resource sleeping (for tsleep) */
|
||||
int lk_timo; /* maximum sleep time (for tsleep) */
|
||||
pid_t lk_lockholder; /* pid of exclusive lock holder */
|
||||
};
|
||||
/*
|
||||
* Lock request types:
|
||||
* LK_SHARED - get one of many possible shared locks. If a process
|
||||
* holding an exclusive lock requests a shared lock, the exclusive
|
||||
* lock(s) will be downgraded to shared locks.
|
||||
* LK_EXCLUSIVE - stop further shared locks, when they are cleared,
|
||||
* grant a pending upgrade if it exists, then grant an exclusive
|
||||
* lock. Only one exclusive lock may exist at a time, except that
|
||||
* a process holding an exclusive lock may get additional exclusive
|
||||
* locks if it explicitly sets the LK_CANRECURSE flag in the lock
|
||||
* request, or if the LK_CANRECUSE flag was set when the lock was
|
||||
* initialized.
|
||||
* LK_UPGRADE - the process must hold a shared lock that it wants to
|
||||
* have upgraded to an exclusive lock. Other processes may get
|
||||
* exclusive access to the resource between the time that the upgrade
|
||||
* is requested and the time that it is granted.
|
||||
* LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
|
||||
* have upgraded to an exclusive lock. If the request succeeds, no
|
||||
* other processes will have gotten exclusive access to the resource
|
||||
* between the time that the upgrade is requested and the time that
|
||||
* it is granted. However, if another process has already requested
|
||||
* an upgrade, the request will fail (see error returns below).
|
||||
* LK_DOWNGRADE - the process must hold an exclusive lock that it wants
|
||||
* to have downgraded to a shared lock. If the process holds multiple
|
||||
* (recursive) exclusive locks, they will all be downgraded to shared
|
||||
* locks.
|
||||
* LK_RELEASE - release one instance of a lock.
|
||||
* LK_DRAIN - wait for all activity on the lock to end, then mark it
|
||||
* decommissioned. This feature is used before freeing a lock that
|
||||
* is part of a piece of memory that is about to be freed.
|
||||
*
|
||||
* These are flags that are passed to the lockmgr routine.
|
||||
*/
|
||||
#define LK_TYPE_MASK 0x0000000f /* type of lock sought */
|
||||
#define LK_SHARED 0x00000001 /* shared lock */
|
||||
#define LK_EXCLUSIVE 0x00000002 /* exclusive lock */
|
||||
#define LK_UPGRADE 0x00000003 /* shared-to-exclusive upgrade */
|
||||
#define LK_EXCLUPGRADE 0x00000004 /* first shared-to-exclusive upgrade */
|
||||
#define LK_DOWNGRADE 0x00000005 /* exclusive-to-shared downgrade */
|
||||
#define LK_RELEASE 0x00000006 /* release any type of lock */
|
||||
#define LK_DRAIN 0x00000007 /* wait for all lock activity to end */
|
||||
/*
|
||||
* External lock flags.
|
||||
*
|
||||
* The first three flags may be set in lock_init to set their mode permanently,
|
||||
* or passed in as arguments to the lock manager. The LK_REENABLE flag may be
|
||||
* set only at the release of a lock obtained by drain.
|
||||
*/
|
||||
#define LK_EXTFLG_MASK 0x00000070 /* mask of external flags */
|
||||
#define LK_NOWAIT 0x00000010 /* do not sleep to await lock */
|
||||
#define LK_SLEEPFAIL 0x00000020 /* sleep, then return failure */
|
||||
#define LK_CANRECURSE 0x00000040 /* allow recursive exclusive lock */
|
||||
#define LK_REENABLE 0x00000080 /* lock is be reenabled after drain */
|
||||
/*
|
||||
* Internal lock flags.
|
||||
*
|
||||
* These flags are used internally to the lock manager.
|
||||
*/
|
||||
#define LK_WANT_UPGRADE 0x00000100 /* waiting for share-to-excl upgrade */
|
||||
#define LK_WANT_EXCL 0x00000200 /* exclusive lock sought */
|
||||
#define LK_HAVE_EXCL 0x00000400 /* exclusive lock obtained */
|
||||
#define LK_WAITDRAIN 0x00000800 /* process waiting for lock to drain */
|
||||
#define LK_DRAINING 0x00004000 /* lock is being drained */
|
||||
#define LK_DRAINED 0x00008000 /* lock has been decommissioned */
|
||||
/*
|
||||
* Control flags
|
||||
*
|
||||
* Non-persistent external flags.
|
||||
*/
|
||||
#define LK_INTERLOCK 0x00010000 /* unlock passed simple lock after
|
||||
getting lk_interlock */
|
||||
#define LK_RETRY 0x00020000 /* vn_lock: retry until locked */
|
||||
|
||||
/*
|
||||
* Lock return status.
|
||||
*
|
||||
* Successfully obtained locks return 0. Locks will always succeed
|
||||
* unless one of the following is true:
|
||||
* LK_FORCEUPGRADE is requested and some other process has already
|
||||
* requested a lock upgrade (returns EBUSY).
|
||||
* LK_WAIT is set and a sleep would be required (returns EBUSY).
|
||||
* LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
|
||||
* PCATCH is set in lock priority and a signal arrives (returns
|
||||
* either EINTR or ERESTART if system calls is to be restarted).
|
||||
* Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
|
||||
* A failed lock attempt always returns a non-zero error value. No lock
|
||||
* is held after an error return (in particular, a failed LK_UPGRADE
|
||||
* or LK_FORCEUPGRADE will have released its shared access lock).
|
||||
*/
|
||||
|
||||
/*
|
||||
* Indicator that no process holds exclusive lock
|
||||
*/
|
||||
#define LK_KERNPROC ((pid_t) -2)
|
||||
#define LK_NOPROC ((pid_t) -1)
|
||||
|
||||
struct proc;
|
||||
|
||||
void lockinit __P((struct lock *, int prio, char *wmesg, int timo,
|
||||
int flags));
|
||||
int lockmgr __P((__volatile struct lock *, u_int flags,
|
||||
struct simplelock *, struct proc *p));
|
||||
int lockstatus __P((struct lock *));
|
||||
|
||||
#ifdef DEBUG
|
||||
void _simple_unlock __P((__volatile struct simplelock *alp, const char *, int));
|
||||
#define simple_unlock(alp) _simple_unlock(alp, __FILE__, __LINE__)
|
||||
int _simple_lock_try __P((__volatile struct simplelock *alp, const char *, int));
|
||||
#define simple_lock_try(alp) _simple_lock_try(alp, __FILE__, __LINE__)
|
||||
void _simple_lock __P((__volatile struct simplelock *alp, const char *, int));
|
||||
#define simple_lock(alp) _simple_lock(alp, __FILE__, __LINE__)
|
||||
void simple_lock_init __P((struct simplelock *alp));
|
||||
#else /* !DEBUG */
|
||||
#if NCPUS == 1 /* no multiprocessor locking is necessary */
|
||||
#define simple_lock_init(alp)
|
||||
#define simple_lock(alp)
|
||||
#define simple_lock_try(alp) (1) /* always succeeds */
|
||||
#define simple_unlock(alp)
|
||||
#endif /* NCPUS == 1 */
|
||||
#endif /* !DEBUG */
|
||||
|
||||
#endif /* !_LOCK_H_ */
|
Loading…
x
Reference in New Issue
Block a user