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NetBSD/sys/kern/kern_lock.c

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/* $NetBSD: kern_lock.c,v 1.129 2007/12/06 17:05:08 ad Exp $ */
/*-
* Copyright (c) 1999, 2000, 2006, 2007 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
* NASA Ames Research Center, and by Andrew Doran.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Ross Harvey.
*
* 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 NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
/*
* 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. 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/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_lock.c,v 1.129 2007/12/06 17:05:08 ad Exp $");
#include "opt_multiprocessor.h"
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lockdebug.h>
#include <sys/cpu.h>
#include <sys/syslog.h>
#include <sys/atomic.h>
#include <machine/stdarg.h>
#include <dev/lockstat.h>
/*
* note that stdarg.h and the ansi style va_start macro is used for both
* ansi and traditional c compiles.
* XXX: this requires that stdarg.h define: va_alist and va_dcl
*/
void lock_printf(const char *fmt, ...)
__attribute__((__format__(__printf__,1,2)));
static int acquire(struct lock **, int *, int, int, int, uintptr_t);
int lock_debug_syslog = 0; /* defaults to printf, but can be patched */
bool kernel_lock_dodebug;
__cpu_simple_lock_t kernel_lock;
#if defined(LOCKDEBUG) || defined(DIAGNOSTIC) /* { */
#define COUNT(lkp, l, cpu_id, x) (l)->l_locks += (x)
#else
#define COUNT(lkp, p, cpu_id, x)
#endif /* LOCKDEBUG || DIAGNOSTIC */ /* } */
#define RETURN_ADDRESS ((uintptr_t)__builtin_return_address(0))
/*
* Acquire a resource.
*/
static int
acquire(struct lock **lkpp, int *s, int extflags,
int drain, int wanted, uintptr_t ra)
{
int error;
struct lock *lkp = *lkpp;
LOCKSTAT_TIMER(slptime);
LOCKSTAT_FLAG(lsflag);
KASSERT(drain || (wanted & LK_WAIT_NONZERO) == 0);
LOCKSTAT_ENTER(lsflag);
for (error = 0; (lkp->lk_flags & wanted) != 0; ) {
if (drain)
lkp->lk_flags |= LK_WAITDRAIN;
else {
lkp->lk_waitcount++;
lkp->lk_flags |= LK_WAIT_NONZERO;
}
LOCKSTAT_START_TIMER(lsflag, slptime);
error = ltsleep(drain ? (void *)&lkp->lk_flags : (void *)lkp,
lkp->lk_prio, lkp->lk_wmesg, lkp->lk_timo,
&lkp->lk_interlock);
LOCKSTAT_STOP_TIMER(lsflag, slptime);
LOCKSTAT_EVENT_RA(lsflag, (void *)(uintptr_t)lkp,
LB_LOCKMGR | LB_SLEEP1, 1, slptime, ra);
if (!drain) {
lkp->lk_waitcount--;
if (lkp->lk_waitcount == 0)
lkp->lk_flags &= ~LK_WAIT_NONZERO;
}
if (error)
break;
if (extflags & LK_SLEEPFAIL) {
error = ENOLCK;
break;
}
}
LOCKSTAT_EXIT(lsflag);
return error;
}
#define SETHOLDER(lkp, pid, lid, cpu_id) \
do { \
(lkp)->lk_lockholder = pid; \
(lkp)->lk_locklwp = lid; \
} while (/*CONSTCOND*/0)
#define WEHOLDIT(lkp, pid, lid, cpu_id) \
((lkp)->lk_lockholder == (pid) && (lkp)->lk_locklwp == (lid))
#define WAKEUP_WAITER(lkp) \
do { \
if (((lkp)->lk_flags & LK_WAIT_NONZERO) != 0) { \
wakeup((lkp)); \
} \
} while (/*CONSTCOND*/0)
#if defined(LOCKDEBUG)
/*
* Lock debug printing routine; can be configured to print to console
* or log to syslog.
*/
void
lock_printf(const char *fmt, ...)
{
char b[150];
va_list ap;
va_start(ap, fmt);
if (lock_debug_syslog)
vlog(LOG_DEBUG, fmt, ap);
else {
vsnprintf(b, sizeof(b), fmt, ap);
printf_nolog("%s", b);
}
va_end(ap);
}
#endif /* LOCKDEBUG */
static void
lockpanic(struct lock *lkp, const char *fmt, ...)
{
char s[150], b[150];
static const char *locktype[] = {
"*0*", "shared", "exclusive", "*3*", "*4*", "downgrade",
"*release*", "drain", "exclother", "*9*", "*10*",
"*11*", "*12*", "*13*", "*14*", "*15*"
};
va_list ap;
va_start(ap, fmt);
vsnprintf(s, sizeof(s), fmt, ap);
va_end(ap);
bitmask_snprintf(lkp->lk_flags, __LK_FLAG_BITS, b, sizeof(b));
panic("%s ("
"type %s flags %s, sharecount %d, exclusivecount %d, "
"recurselevel %d, waitcount %d, wmesg %s"
", lock_addr %p, unlock_addr %p"
")\n",
s, locktype[lkp->lk_flags & LK_TYPE_MASK],
b, lkp->lk_sharecount, lkp->lk_exclusivecount,
lkp->lk_recurselevel, lkp->lk_waitcount, lkp->lk_wmesg,
(void *)lkp->lk_lock_addr, (void *)lkp->lk_unlock_addr
);
}
/*
* Initialize a lock; required before use.
*/
void
lockinit(struct lock *lkp, pri_t prio, const char *wmesg, int timo, int flags)
{
memset(lkp, 0, sizeof(struct lock));
lkp->lk_flags = flags & LK_EXTFLG_MASK;
simple_lock_init(&lkp->lk_interlock);
lkp->lk_lockholder = LK_NOPROC;
lkp->lk_prio = prio;
lkp->lk_timo = timo;
lkp->lk_wmesg = wmesg;
lkp->lk_lock_addr = 0;
lkp->lk_unlock_addr = 0;
}
void
lockdestroy(struct lock *lkp)
{
/* nothing yet */
}
/*
* Determine the status of a lock.
*/
int
lockstatus(struct lock *lkp)
{
int lock_type = 0;
struct lwp *l = curlwp; /* XXX */
pid_t pid;
lwpid_t lid;
cpuid_t cpu_num;
if (l == NULL) {
cpu_num = cpu_number();
pid = LK_KERNPROC;
lid = 0;
} else {
cpu_num = LK_NOCPU;
pid = l->l_proc->p_pid;
lid = l->l_lid;
}
simple_lock(&lkp->lk_interlock);
if (lkp->lk_exclusivecount != 0) {
if (WEHOLDIT(lkp, pid, lid, cpu_num))
lock_type = LK_EXCLUSIVE;
else
lock_type = LK_EXCLOTHER;
} else if (lkp->lk_sharecount != 0)
lock_type = LK_SHARED;
else if (lkp->lk_flags & LK_WANT_EXCL)
lock_type = LK_EXCLOTHER;
simple_unlock(&lkp->lk_interlock);
return (lock_type);
}
/*
* XXX XXX kludge around another kludge..
*
* vfs_shutdown() may be called from interrupt context, either as a result
* of a panic, or from the debugger. It proceeds to call
* sys_sync(&proc0, ...), pretending its running on behalf of proc0
*
* We would like to make an attempt to sync the filesystems in this case, so
* if this happens, we treat attempts to acquire locks specially.
* All locks are acquired on behalf of proc0.
*
* If we've already paniced, we don't block waiting for locks, but
* just barge right ahead since we're already going down in flames.
*/
/*
* 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 to go away.
*/
int
lockmgr(struct lock *lkp, u_int flags, struct simplelock *interlkp)
{
int error;
pid_t pid;
lwpid_t lid;
int extflags;
cpuid_t cpu_num;
struct lwp *l = curlwp;
int lock_shutdown_noblock = 0;
int s = 0;
error = 0;
/* LK_RETRY is for vn_lock, not for lockmgr. */
KASSERT((flags & LK_RETRY) == 0);
KASSERT((l->l_pflag & LP_INTR) == 0 || panicstr != NULL);
simple_lock(&lkp->lk_interlock);
if (flags & LK_INTERLOCK)
simple_unlock(interlkp);
extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
if (l == NULL) {
if (!doing_shutdown) {
panic("lockmgr: no context");
} else {
l = &lwp0;
if (panicstr && (!(flags & LK_NOWAIT))) {
flags |= LK_NOWAIT;
lock_shutdown_noblock = 1;
}
}
}
lid = l->l_lid;
pid = l->l_proc->p_pid;
cpu_num = cpu_number();
/*
* 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)) {
#ifdef DIAGNOSTIC /* { */
if (lkp->lk_flags & LK_DRAINED)
lockpanic(lkp, "lockmgr: using decommissioned lock");
if ((flags & LK_TYPE_MASK) != LK_RELEASE ||
WEHOLDIT(lkp, pid, lid, cpu_num) == 0)
lockpanic(lkp, "lockmgr: non-release on draining lock: %d",
flags & LK_TYPE_MASK);
#endif /* DIAGNOSTIC */ /* } */
lkp->lk_flags &= ~LK_DRAINING;
if ((flags & LK_REENABLE) == 0)
lkp->lk_flags |= LK_DRAINED;
}
switch (flags & LK_TYPE_MASK) {
case LK_SHARED:
if (WEHOLDIT(lkp, pid, lid, cpu_num) == 0) {
/*
* If just polling, check to see if we will block.
*/
if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL))) {
error = EBUSY;
break;
}
/*
* Wait for exclusive locks to clear.
*/
error = acquire(&lkp, &s, extflags, 0,
LK_HAVE_EXCL | LK_WANT_EXCL,
RETURN_ADDRESS);
if (error)
break;
lkp->lk_sharecount++;
lkp->lk_flags |= LK_SHARE_NONZERO;
COUNT(lkp, l, cpu_num, 1);
break;
}
/*
* We hold an exclusive lock, so downgrade it to shared.
* An alternative would be to fail with EDEADLK.
*/
lkp->lk_sharecount++;
lkp->lk_flags |= LK_SHARE_NONZERO;
COUNT(lkp, l, cpu_num, 1);
/* fall into downgrade */
case LK_DOWNGRADE:
if (WEHOLDIT(lkp, pid, lid, cpu_num) == 0 ||
lkp->lk_exclusivecount == 0)
lockpanic(lkp, "lockmgr: not holding exclusive lock");
lkp->lk_sharecount += lkp->lk_exclusivecount;
lkp->lk_flags |= LK_SHARE_NONZERO;
lkp->lk_exclusivecount = 0;
lkp->lk_recurselevel = 0;
lkp->lk_flags &= ~LK_HAVE_EXCL;
SETHOLDER(lkp, LK_NOPROC, 0, LK_NOCPU);
#if defined(LOCKDEBUG)
lkp->lk_unlock_addr = RETURN_ADDRESS;
#endif
WAKEUP_WAITER(lkp);
break;
case LK_EXCLUSIVE:
if (WEHOLDIT(lkp, pid, lid, cpu_num)) {
/*
* Recursive lock.
*/
if ((extflags & LK_CANRECURSE) == 0 &&
lkp->lk_recurselevel == 0) {
if (extflags & LK_RECURSEFAIL) {
error = EDEADLK;
break;
} else
lockpanic(lkp, "lockmgr: locking against myself");
}
lkp->lk_exclusivecount++;
if (extflags & LK_SETRECURSE &&
lkp->lk_recurselevel == 0)
lkp->lk_recurselevel = lkp->lk_exclusivecount;
COUNT(lkp, l, cpu_num, 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_SHARE_NONZERO))) {
error = EBUSY;
break;
}
/*
* Try to acquire the want_exclusive flag.
*/
error = acquire(&lkp, &s, extflags, 0,
LK_HAVE_EXCL | LK_WANT_EXCL, RETURN_ADDRESS);
if (error)
break;
lkp->lk_flags |= LK_WANT_EXCL;
/*
* Wait for shared locks to finish.
*/
error = acquire(&lkp, &s, extflags, 0,
LK_HAVE_EXCL | LK_SHARE_NONZERO,
RETURN_ADDRESS);
lkp->lk_flags &= ~LK_WANT_EXCL;
if (error) {
WAKEUP_WAITER(lkp);
break;
}
lkp->lk_flags |= LK_HAVE_EXCL;
SETHOLDER(lkp, pid, lid, cpu_num);
#if defined(LOCKDEBUG)
lkp->lk_lock_addr = RETURN_ADDRESS;
#endif
if (lkp->lk_exclusivecount != 0)
lockpanic(lkp, "lockmgr: non-zero exclusive count");
lkp->lk_exclusivecount = 1;
if (extflags & LK_SETRECURSE)
lkp->lk_recurselevel = 1;
COUNT(lkp, l, cpu_num, 1);
break;
case LK_RELEASE:
if (lkp->lk_exclusivecount != 0) {
if (WEHOLDIT(lkp, pid, lid, cpu_num) == 0) {
lockpanic(lkp, "lockmgr: pid %d.%d, not "
"exclusive lock holder %d.%d "
"unlocking", pid, lid,
lkp->lk_lockholder,
lkp->lk_locklwp);
}
if (lkp->lk_exclusivecount == lkp->lk_recurselevel)
lkp->lk_recurselevel = 0;
lkp->lk_exclusivecount--;
COUNT(lkp, l, cpu_num, -1);
if (lkp->lk_exclusivecount == 0) {
lkp->lk_flags &= ~LK_HAVE_EXCL;
SETHOLDER(lkp, LK_NOPROC, 0, LK_NOCPU);
#if defined(LOCKDEBUG)
lkp->lk_unlock_addr = RETURN_ADDRESS;
#endif
}
} else if (lkp->lk_sharecount != 0) {
lkp->lk_sharecount--;
if (lkp->lk_sharecount == 0)
lkp->lk_flags &= ~LK_SHARE_NONZERO;
COUNT(lkp, l, cpu_num, -1);
}
#ifdef DIAGNOSTIC
else
lockpanic(lkp, "lockmgr: release of unlocked lock!");
#endif
WAKEUP_WAITER(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 (WEHOLDIT(lkp, pid, lid, cpu_num))
lockpanic(lkp, "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_SHARE_NONZERO | LK_WAIT_NONZERO))) {
error = EBUSY;
break;
}
error = acquire(&lkp, &s, extflags, 1,
LK_HAVE_EXCL | LK_WANT_EXCL |
LK_SHARE_NONZERO | LK_WAIT_NONZERO,
RETURN_ADDRESS);
if (error)
break;
lkp->lk_flags |= LK_HAVE_EXCL;
if ((extflags & LK_RESURRECT) == 0)
lkp->lk_flags |= LK_DRAINING;
SETHOLDER(lkp, pid, lid, cpu_num);
#if defined(LOCKDEBUG)
lkp->lk_lock_addr = RETURN_ADDRESS;
#endif
lkp->lk_exclusivecount = 1;
/* XXX unlikely that we'd want this */
if (extflags & LK_SETRECURSE)
lkp->lk_recurselevel = 1;
COUNT(lkp, l, cpu_num, 1);
break;
default:
simple_unlock(&lkp->lk_interlock);
lockpanic(lkp, "lockmgr: unknown locktype request %d",
flags & LK_TYPE_MASK);
/* NOTREACHED */
}
if ((lkp->lk_flags & LK_WAITDRAIN) != 0 &&
((lkp->lk_flags &
(LK_HAVE_EXCL | LK_WANT_EXCL |
LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0)) {
lkp->lk_flags &= ~LK_WAITDRAIN;
wakeup(&lkp->lk_flags);
}
/*
* Note that this panic will be a recursive panic, since
* we only set lock_shutdown_noblock above if panicstr != NULL.
*/
if (error && lock_shutdown_noblock)
lockpanic(lkp, "lockmgr: deadlock (see previous panic)");
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(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 ",
lkp->lk_wmesg, lkp->lk_exclusivecount);
printf("pid %d.%d", lkp->lk_lockholder,
lkp->lk_locklwp);
} else
printf(" not locked");
if (lkp->lk_waitcount > 0)
printf(" with %d pending", lkp->lk_waitcount);
}
#if defined(LOCKDEBUG)
void
assert_sleepable(struct simplelock *interlock, const char *msg)
{
if (panicstr != NULL)
return;
LOCKDEBUG_BARRIER(&kernel_lock, 1);
if (CURCPU_IDLE_P() && !cold) {
panic("assert_sleepable: idle");
}
}
#endif
/*
* rump doesn't need the kernel lock so force it out. We cannot
* currently easily include it for compilation because of
* a) SPINLOCK_* b) membar_producer(). They are defined in different
* places / way for each arch, so just simply do not bother to
* fight a lot for no gain (i.e. pain but still no gain).
*/
#ifndef _RUMPKERNEL
/*
* Functions for manipulating the kernel_lock. We put them here
* so that they show up in profiles.
*/
#define _KERNEL_LOCK_ABORT(msg) \
LOCKDEBUG_ABORT(&kernel_lock, &_kernel_lock_ops, __func__, msg)
#ifdef LOCKDEBUG
#define _KERNEL_LOCK_ASSERT(cond) \
do { \
if (!(cond)) \
_KERNEL_LOCK_ABORT("assertion failed: " #cond); \
} while (/* CONSTCOND */ 0)
#else
#define _KERNEL_LOCK_ASSERT(cond) /* nothing */
#endif
void _kernel_lock_dump(volatile void *);
lockops_t _kernel_lock_ops = {
"Kernel lock",
0,
_kernel_lock_dump
};
/*
* Initialize the kernel lock.
*/
void
kernel_lock_init(void)
{
__cpu_simple_lock_init(&kernel_lock);
kernel_lock_dodebug = LOCKDEBUG_ALLOC(&kernel_lock, &_kernel_lock_ops,
RETURN_ADDRESS);
}
/*
* Print debugging information about the kernel lock.
*/
void
_kernel_lock_dump(volatile void *junk)
{
struct cpu_info *ci = curcpu();
(void)junk;
printf_nolog("curcpu holds : %18d wanted by: %#018lx\n",
ci->ci_biglock_count, (long)ci->ci_biglock_wanted);
}
/*
* Acquire 'nlocks' holds on the kernel lock. If 'l' is non-null, the
* acquisition is from process context.
*/
void
_kernel_lock(int nlocks, struct lwp *l)
{
struct cpu_info *ci = curcpu();
LOCKSTAT_TIMER(spintime);
LOCKSTAT_FLAG(lsflag);
struct lwp *owant;
#ifdef LOCKDEBUG
u_int spins;
#endif
int s;
if (nlocks == 0)
return;
_KERNEL_LOCK_ASSERT(nlocks > 0);
l = curlwp;
if (ci->ci_biglock_count != 0) {
_KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(&kernel_lock));
ci->ci_biglock_count += nlocks;
l->l_blcnt += nlocks;
return;
}
_KERNEL_LOCK_ASSERT(l->l_blcnt == 0);
LOCKDEBUG_WANTLOCK(kernel_lock_dodebug, &kernel_lock, RETURN_ADDRESS,
0);
s = splvm();
if (__cpu_simple_lock_try(&kernel_lock)) {
ci->ci_biglock_count = nlocks;
l->l_blcnt = nlocks;
LOCKDEBUG_LOCKED(kernel_lock_dodebug, &kernel_lock,
RETURN_ADDRESS, 0);
splx(s);
return;
}
LOCKSTAT_ENTER(lsflag);
LOCKSTAT_START_TIMER(lsflag, spintime);
/*
* Before setting ci_biglock_wanted we must post a store
* fence (see kern_mutex.c). This is accomplished by the
* __cpu_simple_lock_try() above.
*/
owant = ci->ci_biglock_wanted;
ci->ci_biglock_wanted = curlwp; /* XXXAD */
#ifdef LOCKDEBUG
spins = 0;
#endif
do {
splx(s);
while (__SIMPLELOCK_LOCKED_P(&kernel_lock)) {
#ifdef LOCKDEBUG
if (SPINLOCK_SPINOUT(spins))
_KERNEL_LOCK_ABORT("spinout");
#endif
SPINLOCK_BACKOFF_HOOK;
SPINLOCK_SPIN_HOOK;
}
(void)splvm();
} while (!__cpu_simple_lock_try(&kernel_lock));
ci->ci_biglock_wanted = owant;
ci->ci_biglock_count = nlocks;
l->l_blcnt = nlocks;
LOCKSTAT_STOP_TIMER(lsflag, spintime);
LOCKDEBUG_LOCKED(kernel_lock_dodebug, &kernel_lock, RETURN_ADDRESS, 0);
splx(s);
/*
* Again, another store fence is required (see kern_mutex.c).
*/
membar_producer();
if (owant == NULL) {
LOCKSTAT_EVENT(lsflag, &kernel_lock, LB_KERNEL_LOCK | LB_SPIN,
1, spintime);
}
LOCKSTAT_EXIT(lsflag);
}
/*
* Release 'nlocks' holds on the kernel lock. If 'nlocks' is zero, release
* all holds. If 'l' is non-null, the release is from process context.
*/
void
_kernel_unlock(int nlocks, struct lwp *l, int *countp)
{
struct cpu_info *ci = curcpu();
u_int olocks;
int s;
l = curlwp;
_KERNEL_LOCK_ASSERT(nlocks < 2);
olocks = l->l_blcnt;
if (olocks == 0) {
_KERNEL_LOCK_ASSERT(nlocks <= 0);
if (countp != NULL)
*countp = 0;
return;
}
_KERNEL_LOCK_ASSERT(__SIMPLELOCK_LOCKED_P(&kernel_lock));
if (nlocks == 0)
nlocks = olocks;
else if (nlocks == -1) {
nlocks = 1;
_KERNEL_LOCK_ASSERT(olocks == 1);
}
_KERNEL_LOCK_ASSERT(ci->ci_biglock_count >= l->l_blcnt);
l->l_blcnt -= nlocks;
if (ci->ci_biglock_count == nlocks) {
s = splvm();
LOCKDEBUG_UNLOCKED(kernel_lock_dodebug, &kernel_lock,
RETURN_ADDRESS, 0);
ci->ci_biglock_count = 0;
__cpu_simple_unlock(&kernel_lock);
splx(s);
} else
ci->ci_biglock_count -= nlocks;
if (countp != NULL)
*countp = olocks;
}
#endif /* !_RUMPKERNEL */
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