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/* $OpenBSD: lock_machdep.c,v 1.13 2013/12/05 01:28:45 uebayasi Exp $ */
/* $NetBSD: lock_machdep.c,v 1.1.2.3 2000/05/03 14:40:30 sommerfeld Exp $ */
/*-
* Copyright (c) 1998, 1999 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.
*
* 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.
*
* 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.
*/
/*
* Machine-dependent spin lock operations.
*/
#include <sys/param.h>
#include <sys/lock.h>
#include <sys/systm.h>
#include <machine/atomic.h>
#include <machine/lock.h>
#include <machine/cpufunc.h>
#include <ddb/db_output.h>
int
rw_cas_486(volatile unsigned long *p, unsigned long o, unsigned long n)
{
return (i486_atomic_cas_int((u_int *)p, o, n) != o);
}
#ifdef MULTIPROCESSOR
void
__mp_lock_init(struct __mp_lock *lock)
{
lock->mpl_cpu = NULL;
lock->mpl_count = 0;
}
#if defined(MP_LOCKDEBUG)
#ifndef DDB
#error "MP_LOCKDEBUG requires DDB"
#endif
extern void Debugger(void);
extern int db_printf(const char *, ...)
__attribute__((__format__(__kprintf__,1,2)));
/* CPU-dependent timing, needs this to be settable from ddb. */
extern int __mp_lock_spinout;
#endif
static __inline void
__mp_lock_spin(struct __mp_lock *mpl)
{
#ifndef MP_LOCKDEBUG
while (mpl->mpl_count != 0)
SPINLOCK_SPIN_HOOK;
#else
int ticks = __mp_lock_spinout;
while (mpl->mpl_count != 0 && --ticks > 0)
SPINLOCK_SPIN_HOOK;
if (ticks == 0) {
db_printf("__mp_lock(0x%x): lock spun out", mpl);
Debugger();
}
#endif
}
void
__mp_lock(struct __mp_lock *mpl)
{
/*
* Please notice that mpl_count gets incremented twice for the
* first lock. This is on purpose. The way we release the lock
* in mp_unlock is to decrement the mpl_count and then check if
* the lock should be released. Since mpl_count is what we're
* spinning on, decrementing it in mpl_unlock to 0 means that
* we can't clear mpl_cpu, because we're no longer holding the
* lock. In theory mpl_cpu doesn't need to be cleared, but it's
* safer to clear it and besides, setting mpl_count to 2 on the
* first lock makes most of this code much simpler.
*/
while (1) {
int ef = read_eflags();
disable_intr();
if (i486_atomic_cas_int(&mpl->mpl_count, 0, 1) == 0) {
mpl->mpl_cpu = curcpu();
}
if (mpl->mpl_cpu == curcpu()) {
mpl->mpl_count++;
write_eflags(ef);
break;
}
write_eflags(ef);
__mp_lock_spin(mpl);
}
}
void
__mp_unlock(struct __mp_lock *mpl)
{
int ef = read_eflags();
#ifdef MP_LOCKDEBUG
if (mpl->mpl_cpu != curcpu()) {
db_printf("__mp_unlock(%p): not held lock\n", mpl);
Debugger();
}
#endif
disable_intr();
if (--mpl->mpl_count == 1) {
mpl->mpl_cpu = NULL;
mpl->mpl_count = 0;
}
write_eflags(ef);
}
int
__mp_release_all(struct __mp_lock *mpl)
{
int rv = mpl->mpl_count - 1;
int ef = read_eflags();
#ifdef MP_LOCKDEBUG
if (mpl->mpl_cpu != curcpu()) {
db_printf("__mp_release_all(%p): not held lock\n", mpl);
Debugger();
}
#endif
disable_intr();
mpl->mpl_cpu = NULL;
mpl->mpl_count = 0;
write_eflags(ef);
return (rv);
}
int
__mp_release_all_but_one(struct __mp_lock *mpl)
{
int rv = mpl->mpl_count - 2;
#ifdef MP_LOCKDEBUG
if (mpl->mpl_cpu != curcpu()) {
db_printf("__mp_release_all_but_one(%p): not held lock\n", mpl);
Debugger();
}
#endif
mpl->mpl_count = 2;
return (rv);
}
void
__mp_acquire_count(struct __mp_lock *mpl, int count)
{
while (count--)
__mp_lock(mpl);
}
int
__mp_lock_held(struct __mp_lock *mpl)
{
return mpl->mpl_cpu == curcpu();
}
#endif
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