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/* $OpenBSD: kern_lock.c,v 1.51 2017/10/17 14:25:35 visa Exp $ */
/*
* 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/param.h>
#include <sys/systm.h>
#include <sys/sched.h>
#include <sys/atomic.h>
#include <sys/witness.h>
#include <ddb/db_output.h>
#ifdef MP_LOCKDEBUG
#ifndef DDB
#error "MP_LOCKDEBUG requires DDB"
#endif
/* CPU-dependent timing, this needs to be settable from ddb. */
int __mp_lock_spinout = 200000000;
#endif /* MP_LOCKDEBUG */
#if defined(MULTIPROCESSOR) || defined(WITNESS)
struct __mp_lock kernel_lock;
#endif
#ifdef MULTIPROCESSOR
/*
* Functions for manipulating the kernel_lock. We put them here
* so that they show up in profiles.
*/
void
_kernel_lock_init(void)
{
__mp_lock_init(&kernel_lock);
}
/*
* Acquire/release the kernel lock. Intended for use in the scheduler
* and the lower half of the kernel.
*/
void
_kernel_lock(const char *file, int line)
{
SCHED_ASSERT_UNLOCKED();
#ifdef WITNESS
___mp_lock(&kernel_lock, file, line);
#else
__mp_lock(&kernel_lock);
#endif
}
void
_kernel_unlock(void)
{
__mp_unlock(&kernel_lock);
}
int
_kernel_lock_held(void)
{
if (panicstr)
return 1;
return (__mp_lock_held(&kernel_lock));
}
#ifdef __USE_MI_MPLOCK
/* Ticket lock implementation */
/*
* Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <machine/cpu.h>
void
___mp_lock_init(struct __mp_lock *mpl, struct lock_type *type)
{
memset(mpl->mpl_cpus, 0, sizeof(mpl->mpl_cpus));
mpl->mpl_users = 0;
mpl->mpl_ticket = 1;
#ifdef WITNESS
mpl->mpl_lock_obj.lo_name = type->lt_name;
mpl->mpl_lock_obj.lo_type = type;
if (mpl == &kernel_lock)
mpl->mpl_lock_obj.lo_flags = LO_WITNESS | LO_INITIALIZED |
LO_SLEEPABLE | (LO_CLASS_KERNEL_LOCK << LO_CLASSSHIFT);
else if (mpl == &sched_lock)
mpl->mpl_lock_obj.lo_flags = LO_WITNESS | LO_INITIALIZED |
LO_RECURSABLE | (LO_CLASS_SCHED_LOCK << LO_CLASSSHIFT);
WITNESS_INIT(&mpl->mpl_lock_obj, type);
#endif
}
static __inline void
__mp_lock_spin(struct __mp_lock *mpl, u_int me)
{
#ifndef MP_LOCKDEBUG
while (mpl->mpl_ticket != me)
CPU_BUSY_CYCLE();
#else
int nticks = __mp_lock_spinout;
while (mpl->mpl_ticket != me) {
CPU_BUSY_CYCLE();
if (--nticks <= 0) {
db_printf("__mp_lock(%p): lock spun out", mpl);
db_enter();
nticks = __mp_lock_spinout;
}
}
#endif
}
void
___mp_lock(struct __mp_lock *mpl LOCK_FL_VARS)
{
struct __mp_lock_cpu *cpu = &mpl->mpl_cpus[cpu_number()];
unsigned long s;
#ifdef WITNESS
if (!__mp_lock_held(mpl))
WITNESS_CHECKORDER(&mpl->mpl_lock_obj,
LOP_EXCLUSIVE | LOP_NEWORDER, file, line, NULL);
#endif
s = intr_disable();
if (cpu->mplc_depth++ == 0)
cpu->mplc_ticket = atomic_inc_int_nv(&mpl->mpl_users);
intr_restore(s);
__mp_lock_spin(mpl, cpu->mplc_ticket);
membar_enter_after_atomic();
WITNESS_LOCK(&mpl->mpl_lock_obj, LOP_EXCLUSIVE, file, line);
}
void
___mp_unlock(struct __mp_lock *mpl LOCK_FL_VARS)
{
struct __mp_lock_cpu *cpu = &mpl->mpl_cpus[cpu_number()];
unsigned long s;
#ifdef MP_LOCKDEBUG
if (!__mp_lock_held(mpl)) {
db_printf("__mp_unlock(%p): not held lock\n", mpl);
db_enter();
}
#endif
WITNESS_UNLOCK(&mpl->mpl_lock_obj, LOP_EXCLUSIVE, file, line);
s = intr_disable();
if (--cpu->mplc_depth == 0) {
membar_exit();
mpl->mpl_ticket++;
}
intr_restore(s);
}
int
___mp_release_all(struct __mp_lock *mpl LOCK_FL_VARS)
{
struct __mp_lock_cpu *cpu = &mpl->mpl_cpus[cpu_number()];
unsigned long s;
int rv;
#ifdef WITNESS
int i;
#endif
s = intr_disable();
rv = cpu->mplc_depth;
#ifdef WITNESS
for (i = 0; i < rv; i++)
WITNESS_UNLOCK(&mpl->mpl_lock_obj, LOP_EXCLUSIVE, file, line);
#endif
cpu->mplc_depth = 0;
membar_exit();
mpl->mpl_ticket++;
intr_restore(s);
return (rv);
}
int
___mp_release_all_but_one(struct __mp_lock *mpl LOCK_FL_VARS)
{
struct __mp_lock_cpu *cpu = &mpl->mpl_cpus[cpu_number()];
int rv = cpu->mplc_depth - 1;
#ifdef WITNESS
int i;
for (i = 0; i < rv; i++)
WITNESS_UNLOCK(&mpl->mpl_lock_obj, LOP_EXCLUSIVE, file, line);
#endif
#ifdef MP_LOCKDEBUG
if (!__mp_lock_held(mpl)) {
db_printf("__mp_release_all_but_one(%p): not held lock\n", mpl);
db_enter();
}
#endif
cpu->mplc_depth = 1;
return (rv);
}
void
___mp_acquire_count(struct __mp_lock *mpl, int count LOCK_FL_VARS)
{
while (count--)
___mp_lock(mpl LOCK_FL_ARGS);
}
int
__mp_lock_held(struct __mp_lock *mpl)
{
struct __mp_lock_cpu *cpu = &mpl->mpl_cpus[cpu_number()];
return (cpu->mplc_ticket == mpl->mpl_ticket && cpu->mplc_depth > 0);
}
#endif /* __USE_MI_MPLOCK */
#endif /* MULTIPROCESSOR */
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