kern_mutex.c

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/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
 *
 * 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. Berkeley Software Design Inc's name may not be used to endorse or
 *    promote products derived from this software without specific prior
 *    written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``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 BERKELEY SOFTWARE DESIGN INC 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.
 *
 *      from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
 *      and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
 */
 
/*
 * Machine independent bits of mutex implementation.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include "opt_adaptive_mutexes.h"
#include "opt_ddb.h"
#include "opt_hwpmc_hooks.h"
#include "opt_sched.h"
 
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bus.h>
#include <sys/conf.h>
#include <sys/kdb.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sched.h>
#include <sys/sbuf.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <sys/turnstile.h>
#include <sys/vmmeter.h>
#include <sys/lock_profile.h>
 
#include <machine/atomic.h>
#include <machine/bus.h>
#include <machine/cpu.h>
 
#include <ddb/ddb.h>
 
#include <fs/devfs/devfs_int.h>
 
#include <vm/vm.h>
#include <vm/vm_extern.h>
 
#if defined(SMP) && !defined(NO_ADAPTIVE_MUTEXES)
#define ADAPTIVE_MUTEXES
#endif
 
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
PMC_SOFT_DEFINE( , , lock, failed);
#endif
 
/*
 * Return the mutex address when the lock cookie address is provided.
 * This functionality assumes that struct mtx* have a member named mtx_lock.
 */
#define mtxlock2mtx(c)  (__containerof(c, struct mtx, mtx_lock))
 
/*
 * Internal utility macros.
 */
#define mtx_unowned(m)  ((m)->mtx_lock == MTX_UNOWNED)
 
#define mtx_destroyed(m) ((m)->mtx_lock == MTX_DESTROYED)
 
static void     assert_mtx(const struct lock_object *lock, int what);
#ifdef DDB
static void     db_show_mtx(const struct lock_object *lock);
#endif
static void     lock_mtx(struct lock_object *lock, uintptr_t how);
static void     lock_spin(struct lock_object *lock, uintptr_t how);
#ifdef KDTRACE_HOOKS
static int      owner_mtx(const struct lock_object *lock,
                    struct thread **owner);
#endif
static uintptr_t unlock_mtx(struct lock_object *lock);
static uintptr_t unlock_spin(struct lock_object *lock);
 
/*
 * Lock classes for sleep and spin mutexes.
 */
struct lock_class lock_class_mtx_sleep = {
        .lc_name = "sleep mutex",
        .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
        .lc_assert = assert_mtx,
#ifdef DDB
        .lc_ddb_show = db_show_mtx,
#endif
        .lc_lock = lock_mtx,
        .lc_unlock = unlock_mtx,
#ifdef KDTRACE_HOOKS
        .lc_owner = owner_mtx,
#endif
};
struct lock_class lock_class_mtx_spin = {
        .lc_name = "spin mutex",
        .lc_flags = LC_SPINLOCK | LC_RECURSABLE,
        .lc_assert = assert_mtx,
#ifdef DDB
        .lc_ddb_show = db_show_mtx,
#endif
        .lc_lock = lock_spin,
        .lc_unlock = unlock_spin,
#ifdef KDTRACE_HOOKS
        .lc_owner = owner_mtx,
#endif
};
 
#ifdef ADAPTIVE_MUTEXES
#ifdef MUTEX_CUSTOM_BACKOFF
static SYSCTL_NODE(_debug, OID_AUTO, mtx, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
    "mtx debugging");
 
static struct lock_delay_config __read_frequently mtx_delay;
 
SYSCTL_U16(_debug_mtx, OID_AUTO, delay_base, CTLFLAG_RW, &mtx_delay.base,
    0, "");
SYSCTL_U16(_debug_mtx, OID_AUTO, delay_max, CTLFLAG_RW, &mtx_delay.max,
    0, "");
 
LOCK_DELAY_SYSINIT_DEFAULT(mtx_delay);
#else
#define mtx_delay       locks_delay
#endif
#endif
 
#ifdef MUTEX_SPIN_CUSTOM_BACKOFF
static SYSCTL_NODE(_debug, OID_AUTO, mtx_spin,
    CTLFLAG_RD | CTLFLAG_MPSAFE, NULL,
    "mtx spin debugging");
 
static struct lock_delay_config __read_frequently mtx_spin_delay;
 
SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_base, CTLFLAG_RW,
    &mtx_spin_delay.base, 0, "");
SYSCTL_INT(_debug_mtx_spin, OID_AUTO, delay_max, CTLFLAG_RW,
    &mtx_spin_delay.max, 0, "");
 
LOCK_DELAY_SYSINIT_DEFAULT(mtx_spin_delay);
#else
#define mtx_spin_delay  locks_delay
#endif
 
/*
 * System-wide mutexes
 */
struct mtx blocked_lock;
struct mtx __exclusive_cache_line Giant;
 
static void _mtx_lock_indefinite_check(struct mtx *, struct lock_delay_arg *);
 
void
assert_mtx(const struct lock_object *lock, int what)
{
 
        /*
         * Treat LA_LOCKED as if LA_XLOCKED was asserted.
         *
         * Some callers of lc_assert uses LA_LOCKED to indicate that either
         * a shared lock or write lock was held, while other callers uses
         * the more strict LA_XLOCKED (used as MA_OWNED).
         *
         * Mutex is the only lock class that can not be shared, as a result,
         * we can reasonably consider the caller really intends to assert
         * LA_XLOCKED when they are asserting LA_LOCKED on a mutex object.
         */
        if (what & LA_LOCKED) {
                what &= ~LA_LOCKED;
                what |= LA_XLOCKED;
        }
        mtx_assert((const struct mtx *)lock, what);
}
 
void
lock_mtx(struct lock_object *lock, uintptr_t how)
{
 
        mtx_lock((struct mtx *)lock);
}
 
void
lock_spin(struct lock_object *lock, uintptr_t how)
{
 
        mtx_lock_spin((struct mtx *)lock);
}
 
uintptr_t
unlock_mtx(struct lock_object *lock)
{
        struct mtx *m;
 
        m = (struct mtx *)lock;
        mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
        mtx_unlock(m);
        return (0);
}
 
uintptr_t
unlock_spin(struct lock_object *lock)
{
        struct mtx *m;
 
        m = (struct mtx *)lock;
        mtx_assert(m, MA_OWNED | MA_NOTRECURSED);
        mtx_unlock_spin(m);
        return (0);
}
 
#ifdef KDTRACE_HOOKS
int
owner_mtx(const struct lock_object *lock, struct thread **owner)
{
        const struct mtx *m;
        uintptr_t x;
 
        m = (const struct mtx *)lock;
        x = m->mtx_lock;
        *owner = (struct thread *)(x & ~MTX_FLAGMASK);
        return (*owner != NULL);
}
#endif
 
/*
 * Function versions of the inlined __mtx_* macros.  These are used by
 * modules and can also be called from assembly language if needed.
 */
void
__mtx_lock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
{
        struct mtx *m;
        uintptr_t tid, v;
 
        m = mtxlock2mtx(c);
 
        KASSERT(kdb_active != 0 || SCHEDULER_STOPPED() ||
            !TD_IS_IDLETHREAD(curthread),
            ("mtx_lock() by idle thread %p on sleep mutex %s @ %s:%d",
            curthread, m->lock_object.lo_name, file, line));
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_lock() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
            ("mtx_lock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
            file, line));
        WITNESS_CHECKORDER(&m->lock_object, (opts & ~MTX_RECURSE) |
            LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
 
        tid = (uintptr_t)curthread;
        v = MTX_UNOWNED;
        if (!_mtx_obtain_lock_fetch(m, &v, tid))
                _mtx_lock_sleep(m, v, opts, file, line);
        else
                LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
                    m, 0, 0, file, line);
        LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
            line);
        WITNESS_LOCK(&m->lock_object, (opts & ~MTX_RECURSE) | LOP_EXCLUSIVE,
            file, line);
        TD_LOCKS_INC(curthread);
}
 
void
__mtx_unlock_flags(volatile uintptr_t *c, int opts, const char *file, int line)
{
        struct mtx *m;
 
        m = mtxlock2mtx(c);
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_unlock() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
            ("mtx_unlock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
            file, line));
        WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
        LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
            line);
        mtx_assert(m, MA_OWNED);
 
#ifdef LOCK_PROFILING
        __mtx_unlock_sleep(c, (uintptr_t)curthread, opts, file, line);
#else
        __mtx_unlock(m, curthread, opts, file, line);
#endif
        TD_LOCKS_DEC(curthread);
}
 
void
__mtx_lock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
    int line)
{
        struct mtx *m;
#ifdef SMP
        uintptr_t tid, v;
#endif
 
        m = mtxlock2mtx(c);
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_lock_spin() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
            ("mtx_lock_spin() of sleep mutex %s @ %s:%d",
            m->lock_object.lo_name, file, line));
        if (mtx_owned(m))
                KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
                    (opts & MTX_RECURSE) != 0,
            ("mtx_lock_spin: recursed on non-recursive mutex %s @ %s:%d\n",
                    m->lock_object.lo_name, file, line));
        opts &= ~MTX_RECURSE;
        WITNESS_CHECKORDER(&m->lock_object, opts | LOP_NEWORDER | LOP_EXCLUSIVE,
            file, line, NULL);
#ifdef SMP
        spinlock_enter();
        tid = (uintptr_t)curthread;
        v = MTX_UNOWNED;
        if (!_mtx_obtain_lock_fetch(m, &v, tid))
                _mtx_lock_spin(m, v, opts, file, line);
        else
                LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire,
                    m, 0, 0, file, line);
#else
        __mtx_lock_spin(m, curthread, opts, file, line);
#endif
        LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
            line);
        WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
}
 
int
__mtx_trylock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
    int line)
{
        struct mtx *m;
 
        if (SCHEDULER_STOPPED())
                return (1);
 
        m = mtxlock2mtx(c);
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_trylock_spin() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
            ("mtx_trylock_spin() of sleep mutex %s @ %s:%d",
            m->lock_object.lo_name, file, line));
        KASSERT((opts & MTX_RECURSE) == 0,
            ("mtx_trylock_spin: unsupp. opt MTX_RECURSE on mutex %s @ %s:%d\n",
            m->lock_object.lo_name, file, line));
        if (__mtx_trylock_spin(m, curthread, opts, file, line)) {
                LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 1, file, line);
                WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
                return (1);
        }
        LOCK_LOG_TRY("LOCK", &m->lock_object, opts, 0, file, line);
        return (0);
}
 
void
__mtx_unlock_spin_flags(volatile uintptr_t *c, int opts, const char *file,
    int line)
{
        struct mtx *m;
 
        m = mtxlock2mtx(c);
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_unlock_spin() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
            ("mtx_unlock_spin() of sleep mutex %s @ %s:%d",
            m->lock_object.lo_name, file, line));
        WITNESS_UNLOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
        LOCK_LOG_LOCK("UNLOCK", &m->lock_object, opts, m->mtx_recurse, file,
            line);
        mtx_assert(m, MA_OWNED);
 
        __mtx_unlock_spin(m);
}
 
/*
 * The important part of mtx_trylock{,_flags}()
 * Tries to acquire lock `m.'  If this function is called on a mutex that
 * is already owned, it will recursively acquire the lock.
 */
int
_mtx_trylock_flags_int(struct mtx *m, int opts LOCK_FILE_LINE_ARG_DEF)
{
        struct thread *td;
        uintptr_t tid, v;
#ifdef LOCK_PROFILING
        uint64_t waittime = 0;
        int contested = 0;
#endif
        int rval;
        bool recursed;
 
        td = curthread;
        tid = (uintptr_t)td;
        if (SCHEDULER_STOPPED_TD(td))
                return (1);
 
        KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(td),
            ("mtx_trylock() by idle thread %p on sleep mutex %s @ %s:%d",
            curthread, m->lock_object.lo_name, file, line));
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("mtx_trylock() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
            ("mtx_trylock() of spin mutex %s @ %s:%d", m->lock_object.lo_name,
            file, line));
 
        rval = 1;
        recursed = false;
        v = MTX_UNOWNED;
        for (;;) {
                if (_mtx_obtain_lock_fetch(m, &v, tid))
                        break;
                if (v == MTX_UNOWNED)
                        continue;
                if (v == tid &&
                    ((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
                    (opts & MTX_RECURSE) != 0)) {
                        m->mtx_recurse++;
                        atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
                        recursed = true;
                        break;
                }
                rval = 0;
                break;
        }
 
        opts &= ~MTX_RECURSE;
 
        LOCK_LOG_TRY("LOCK", &m->lock_object, opts, rval, file, line);
        if (rval) {
                WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
                    file, line);
                TD_LOCKS_INC(curthread);
                if (!recursed)
                        LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire,
                            m, contested, waittime, file, line);
        }
 
        return (rval);
}
 
int
_mtx_trylock_flags_(volatile uintptr_t *c, int opts, const char *file, int line)
{
        struct mtx *m;
 
        m = mtxlock2mtx(c);
        return (_mtx_trylock_flags_int(m, opts LOCK_FILE_LINE_ARG));
}
 
/*
 * __mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
 *
 * We call this if the lock is either contested (i.e. we need to go to
 * sleep waiting for it), or if we need to recurse on it.
 */
#if LOCK_DEBUG > 0
void
__mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v, int opts, const char *file,
    int line)
#else
void
__mtx_lock_sleep(volatile uintptr_t *c, uintptr_t v)
#endif
{
        struct thread *td;
        struct mtx *m;
        struct turnstile *ts;
        uintptr_t tid;
        struct thread *owner;
#ifdef LOCK_PROFILING
        int contested = 0;
        uint64_t waittime = 0;
#endif
#if defined(ADAPTIVE_MUTEXES) || defined(KDTRACE_HOOKS)
        struct lock_delay_arg lda;
#endif
#ifdef KDTRACE_HOOKS
        u_int sleep_cnt = 0;
        int64_t sleep_time = 0;
        int64_t all_time = 0;
#endif
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        int doing_lockprof = 0;
#endif
 
        td = curthread;
        tid = (uintptr_t)td;
        m = mtxlock2mtx(c);
 
#ifdef KDTRACE_HOOKS
        if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
                while (v == MTX_UNOWNED) {
                        if (_mtx_obtain_lock_fetch(m, &v, tid))
                                goto out_lockstat;
                }
                doing_lockprof = 1;
                all_time -= lockstat_nsecs(&m->lock_object);
        }
#endif
#ifdef LOCK_PROFILING
        doing_lockprof = 1;
#endif
 
        if (SCHEDULER_STOPPED_TD(td))
                return;
 
        if (__predict_false(v == MTX_UNOWNED))
                v = MTX_READ_VALUE(m);
 
        if (__predict_false(lv_mtx_owner(v) == td)) {
                KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) != 0 ||
                    (opts & MTX_RECURSE) != 0,
            ("_mtx_lock_sleep: recursed on non-recursive mutex %s @ %s:%d\n",
                    m->lock_object.lo_name, file, line));
#if LOCK_DEBUG > 0
                opts &= ~MTX_RECURSE;
#endif
                m->mtx_recurse++;
                atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
                if (LOCK_LOG_TEST(&m->lock_object, opts))
                        CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
                return;
        }
#if LOCK_DEBUG > 0
        opts &= ~MTX_RECURSE;
#endif
 
#if defined(ADAPTIVE_MUTEXES)
        lock_delay_arg_init(&lda, &mtx_delay);
#elif defined(KDTRACE_HOOKS)
        lock_delay_arg_init_noadapt(&lda);
#endif
 
#ifdef HWPMC_HOOKS
        PMC_SOFT_CALL( , , lock, failed);
#endif
        lock_profile_obtain_lock_failed(&m->lock_object, false,
                    &contested, &waittime);
        if (LOCK_LOG_TEST(&m->lock_object, opts))
                CTR4(KTR_LOCK,
                    "_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
                    m->lock_object.lo_name, (void *)m->mtx_lock, file, line);
 
        for (;;) {
                if (v == MTX_UNOWNED) {
                        if (_mtx_obtain_lock_fetch(m, &v, tid))
                                break;
                        continue;
                }
#ifdef KDTRACE_HOOKS
                lda.spin_cnt++;
#endif
#ifdef ADAPTIVE_MUTEXES
                /*
                 * If the owner is running on another CPU, spin until the
                 * owner stops running or the state of the lock changes.
                 */
                owner = lv_mtx_owner(v);
                if (TD_IS_RUNNING(owner)) {
                        if (LOCK_LOG_TEST(&m->lock_object, 0))
                                CTR3(KTR_LOCK,
                                    "%s: spinning on %p held by %p",
                                    __func__, m, owner);
                        KTR_STATE1(KTR_SCHED, "thread",
                            sched_tdname((struct thread *)tid),
                            "spinning", "lockname:\"%s\"",
                            m->lock_object.lo_name);
                        do {
                                lock_delay(&lda);
                                v = MTX_READ_VALUE(m);
                                owner = lv_mtx_owner(v);
                        } while (v != MTX_UNOWNED && TD_IS_RUNNING(owner));
                        KTR_STATE0(KTR_SCHED, "thread",
                            sched_tdname((struct thread *)tid),
                            "running");
                        continue;
                }
#endif
 
                ts = turnstile_trywait(&m->lock_object);
                v = MTX_READ_VALUE(m);
retry_turnstile:
 
                /*
                 * Check if the lock has been released while spinning for
                 * the turnstile chain lock.
                 */
                if (v == MTX_UNOWNED) {
                        turnstile_cancel(ts);
                        continue;
                }
 
#ifdef ADAPTIVE_MUTEXES
                /*
                 * The current lock owner might have started executing
                 * on another CPU (or the lock could have changed
                 * owners) while we were waiting on the turnstile
                 * chain lock.  If so, drop the turnstile lock and try
                 * again.
                 */
                owner = lv_mtx_owner(v);
                if (TD_IS_RUNNING(owner)) {
                        turnstile_cancel(ts);
                        continue;
                }
#endif
 
                /*
                 * If the mutex isn't already contested and a failure occurs
                 * setting the contested bit, the mutex was either released
                 * or the state of the MTX_RECURSED bit changed.
                 */
                if ((v & MTX_CONTESTED) == 0 &&
                    !atomic_fcmpset_ptr(&m->mtx_lock, &v, v | MTX_CONTESTED)) {
                        goto retry_turnstile;
                }
 
                /*
                 * We definitely must sleep for this lock.
                 */
                mtx_assert(m, MA_NOTOWNED);
 
                /*
                 * Block on the turnstile.
                 */
#ifdef KDTRACE_HOOKS
                sleep_time -= lockstat_nsecs(&m->lock_object);
#endif
#ifndef ADAPTIVE_MUTEXES
                owner = mtx_owner(m);
#endif
                MPASS(owner == mtx_owner(m));
                turnstile_wait(ts, owner, TS_EXCLUSIVE_QUEUE);
#ifdef KDTRACE_HOOKS
                sleep_time += lockstat_nsecs(&m->lock_object);
                sleep_cnt++;
#endif
                v = MTX_READ_VALUE(m);
        }
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        if (__predict_true(!doing_lockprof))
                return;
#endif
#ifdef KDTRACE_HOOKS
        all_time += lockstat_nsecs(&m->lock_object);
        if (sleep_time)
                LOCKSTAT_RECORD1(adaptive__block, m, sleep_time);
 
        /*
         * Only record the loops spinning and not sleeping.
         */
        if (lda.spin_cnt > sleep_cnt)
                LOCKSTAT_RECORD1(adaptive__spin, m, all_time - sleep_time);
out_lockstat:
#endif
        LOCKSTAT_PROFILE_OBTAIN_LOCK_SUCCESS(adaptive__acquire, m, contested,
            waittime, file, line);
}
 
#ifdef SMP
/*
 * _mtx_lock_spin_cookie: the tougher part of acquiring an MTX_SPIN lock.
 *
 * This is only called if we need to actually spin for the lock. Recursion
 * is handled inline.
 */
#if LOCK_DEBUG > 0
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v, int opts,
    const char *file, int line)
#else
void
_mtx_lock_spin_cookie(volatile uintptr_t *c, uintptr_t v)
#endif
{
        struct mtx *m;
        struct lock_delay_arg lda;
        uintptr_t tid;
#ifdef LOCK_PROFILING
        int contested = 0;
        uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
        int64_t spin_time = 0;
#endif
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        int doing_lockprof = 0;
#endif
 
        tid = (uintptr_t)curthread;
        m = mtxlock2mtx(c);
 
#ifdef KDTRACE_HOOKS
        if (LOCKSTAT_PROFILE_ENABLED(adaptive__acquire)) {
                while (v == MTX_UNOWNED) {
                        if (_mtx_obtain_lock_fetch(m, &v, tid))
                                goto out_lockstat;
                }
                doing_lockprof = 1;
                spin_time -= lockstat_nsecs(&m->lock_object);
        }
#endif
#ifdef LOCK_PROFILING
        doing_lockprof = 1;
#endif
 
        if (__predict_false(v == MTX_UNOWNED))
                v = MTX_READ_VALUE(m);
 
        if (__predict_false(v == tid)) {
                m->mtx_recurse++;
                return;
        }
 
        if (SCHEDULER_STOPPED())
                return;
 
        if (LOCK_LOG_TEST(&m->lock_object, opts))
                CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
        KTR_STATE1(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
            "spinning", "lockname:\"%s\"", m->lock_object.lo_name);
 
        lock_delay_arg_init(&lda, &mtx_spin_delay);
 
#ifdef HWPMC_HOOKS
        PMC_SOFT_CALL( , , lock, failed);
#endif
        lock_profile_obtain_lock_failed(&m->lock_object, true, &contested, &waittime);
 
        for (;;) {
                if (v == MTX_UNOWNED) {
                        if (_mtx_obtain_lock_fetch(m, &v, tid))
                                break;
                        continue;
                }
                /* Give interrupts a chance while we spin. */
                spinlock_exit();
                do {
                        if (__predict_true(lda.spin_cnt < 10000000)) {
                                lock_delay(&lda);
                        } else {
                                _mtx_lock_indefinite_check(m, &lda);
                        }
                        v = MTX_READ_VALUE(m);
                } while (v != MTX_UNOWNED);
                spinlock_enter();
        }
 
        if (LOCK_LOG_TEST(&m->lock_object, opts))
                CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
        KTR_STATE0(KTR_SCHED, "thread", sched_tdname((struct thread *)tid),
            "running");
 
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        if (__predict_true(!doing_lockprof))
                return;
#endif
#ifdef KDTRACE_HOOKS
        spin_time += lockstat_nsecs(&m->lock_object);
        if (lda.spin_cnt != 0)
                LOCKSTAT_RECORD1(spin__spin, m, spin_time);
out_lockstat:
#endif
        LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m,
            contested, waittime, file, line);
}
#endif /* SMP */
 
#ifdef INVARIANTS
static void
thread_lock_validate(struct mtx *m, int opts, const char *file, int line)
{
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("thread_lock() of destroyed mutex @ %s:%d", file, line));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
            ("thread_lock() of sleep mutex %s @ %s:%d",
            m->lock_object.lo_name, file, line));
        KASSERT((m->lock_object.lo_flags & LO_RECURSABLE) == 0,
            ("thread_lock: got a recursive mutex %s @ %s:%d\n",
            m->lock_object.lo_name, file, line));
        WITNESS_CHECKORDER(&m->lock_object,
            opts | LOP_NEWORDER | LOP_EXCLUSIVE, file, line, NULL);
}
#else
#define thread_lock_validate(m, opts, file, line) do { } while (0)
#endif
 
#ifndef LOCK_PROFILING
#if LOCK_DEBUG > 0
void
_thread_lock(struct thread *td, int opts, const char *file, int line)
#else
void
_thread_lock(struct thread *td)
#endif
{
        struct mtx *m;
        uintptr_t tid;
 
        tid = (uintptr_t)curthread;
 
        if (__predict_false(LOCKSTAT_PROFILE_ENABLED(spin__acquire)))
                goto slowpath_noirq;
        spinlock_enter();
        m = td->td_lock;
        thread_lock_validate(m, 0, file, line);
        if (__predict_false(m == &blocked_lock))
                goto slowpath_unlocked;
        if (__predict_false(!_mtx_obtain_lock(m, tid)))
                goto slowpath_unlocked;
        if (__predict_true(m == td->td_lock)) {
                WITNESS_LOCK(&m->lock_object, LOP_EXCLUSIVE, file, line);
                return;
        }
        _mtx_release_lock_quick(m);
slowpath_unlocked:
        spinlock_exit();
slowpath_noirq:
#if LOCK_DEBUG > 0
        thread_lock_flags_(td, opts, file, line);
#else
        thread_lock_flags_(td, 0, 0, 0);
#endif
}
#endif
 
void
thread_lock_flags_(struct thread *td, int opts, const char *file, int line)
{
        struct mtx *m;
        uintptr_t tid, v;
        struct lock_delay_arg lda;
#ifdef LOCK_PROFILING
        int contested = 0;
        uint64_t waittime = 0;
#endif
#ifdef KDTRACE_HOOKS
        int64_t spin_time = 0;
#endif
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        int doing_lockprof = 1;
#endif
 
        tid = (uintptr_t)curthread;
 
        if (SCHEDULER_STOPPED()) {
                /*
                 * Ensure that spinlock sections are balanced even when the
                 * scheduler is stopped, since we may otherwise inadvertently
                 * re-enable interrupts while dumping core.
                 */
                spinlock_enter();
                return;
        }
 
        lock_delay_arg_init(&lda, &mtx_spin_delay);
 
#ifdef HWPMC_HOOKS
        PMC_SOFT_CALL( , , lock, failed);
#endif
 
#ifdef LOCK_PROFILING
        doing_lockprof = 1;
#elif defined(KDTRACE_HOOKS)
        doing_lockprof = lockstat_enabled;
#endif
#ifdef KDTRACE_HOOKS
        if (__predict_false(doing_lockprof))
                spin_time -= lockstat_nsecs(&td->td_lock->lock_object);
#endif
        spinlock_enter();
 
        for (;;) {
retry:
                m = td->td_lock;
                thread_lock_validate(m, opts, file, line);
                v = MTX_READ_VALUE(m);
                for (;;) {
                        if (v == MTX_UNOWNED) {
                                if (_mtx_obtain_lock_fetch(m, &v, tid))
                                        break;
                                continue;
                        }
                        MPASS(v != tid);
                        lock_profile_obtain_lock_failed(&m->lock_object, true,
                            &contested, &waittime);
                        /* Give interrupts a chance while we spin. */
                        spinlock_exit();
                        do {
                                if (__predict_true(lda.spin_cnt < 10000000)) {
                                        lock_delay(&lda);
                                } else {
                                        _mtx_lock_indefinite_check(m, &lda);
                                }
                                if (m != td->td_lock) {
                                        spinlock_enter();
                                        goto retry;
                                }
                                v = MTX_READ_VALUE(m);
                        } while (v != MTX_UNOWNED);
                        spinlock_enter();
                }
                if (m == td->td_lock)
                        break;
                _mtx_release_lock_quick(m);
        }
        LOCK_LOG_LOCK("LOCK", &m->lock_object, opts, m->mtx_recurse, file,
            line);
        WITNESS_LOCK(&m->lock_object, opts | LOP_EXCLUSIVE, file, line);
 
#if defined(KDTRACE_HOOKS) || defined(LOCK_PROFILING)
        if (__predict_true(!doing_lockprof))
                return;
#endif
#ifdef KDTRACE_HOOKS
        spin_time += lockstat_nsecs(&m->lock_object);
#endif
        LOCKSTAT_PROFILE_OBTAIN_SPIN_LOCK_SUCCESS(spin__acquire, m, contested,
            waittime, file, line);
#ifdef KDTRACE_HOOKS
        if (lda.spin_cnt != 0)
                LOCKSTAT_RECORD1(thread__spin, m, spin_time);
#endif
}
 
struct mtx *
thread_lock_block(struct thread *td)
{
        struct mtx *lock;
 
        lock = td->td_lock;
        mtx_assert(lock, MA_OWNED);
        td->td_lock = &blocked_lock;
 
        return (lock);
}
 
void
thread_lock_unblock(struct thread *td, struct mtx *new)
{
 
        mtx_assert(new, MA_OWNED);
        KASSERT(td->td_lock == &blocked_lock,
            ("thread %p lock %p not blocked_lock %p",
            td, td->td_lock, &blocked_lock));
        atomic_store_rel_ptr((volatile void *)&td->td_lock, (uintptr_t)new);
}
 
void
thread_lock_block_wait(struct thread *td)
{
 
        while (td->td_lock == &blocked_lock)
                cpu_spinwait();
 
        /* Acquire fence to be certain that all thread state is visible. */
        atomic_thread_fence_acq();
}
 
void
thread_lock_set(struct thread *td, struct mtx *new)
{
        struct mtx *lock;
 
        mtx_assert(new, MA_OWNED);
        lock = td->td_lock;
        mtx_assert(lock, MA_OWNED);
        td->td_lock = new;
        mtx_unlock_spin(lock);
}
 
/*
 * __mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
 *
 * We are only called here if the lock is recursed, contested (i.e. we
 * need to wake up a blocked thread) or lockstat probe is active.
 */
#if LOCK_DEBUG > 0
void
__mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v, int opts,
    const char *file, int line)
#else
void
__mtx_unlock_sleep(volatile uintptr_t *c, uintptr_t v)
#endif
{
        struct mtx *m;
        struct turnstile *ts;
        uintptr_t tid;
 
        if (SCHEDULER_STOPPED())
                return;
 
        tid = (uintptr_t)curthread;
        m = mtxlock2mtx(c);
 
        if (__predict_false(v == tid))
                v = MTX_READ_VALUE(m);
 
        if (__predict_false(v & MTX_RECURSED)) {
                if (--(m->mtx_recurse) == 0)
                        atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
                if (LOCK_LOG_TEST(&m->lock_object, opts))
                        CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
                return;
        }
 
        LOCKSTAT_PROFILE_RELEASE_LOCK(adaptive__release, m);
        if (v == tid && _mtx_release_lock(m, tid))
                return;
 
        /*
         * We have to lock the chain before the turnstile so this turnstile
         * can be removed from the hash list if it is empty.
         */
        turnstile_chain_lock(&m->lock_object);
        _mtx_release_lock_quick(m);
        ts = turnstile_lookup(&m->lock_object);
        MPASS(ts != NULL);
        if (LOCK_LOG_TEST(&m->lock_object, opts))
                CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
        turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
 
        /*
         * This turnstile is now no longer associated with the mutex.  We can
         * unlock the chain lock so a new turnstile may take it's place.
         */
        turnstile_unpend(ts);
        turnstile_chain_unlock(&m->lock_object);
}
 
/*
 * All the unlocking of MTX_SPIN locks is done inline.
 * See the __mtx_unlock_spin() macro for the details.
 */
 
/*
 * The backing function for the INVARIANTS-enabled mtx_assert()
 */
#ifdef INVARIANT_SUPPORT
void
__mtx_assert(const volatile uintptr_t *c, int what, const char *file, int line)
{
        const struct mtx *m;
 
        if (KERNEL_PANICKED() || dumping || SCHEDULER_STOPPED())
                return;
 
        m = mtxlock2mtx(c);
 
        switch (what) {
        case MA_OWNED:
        case MA_OWNED | MA_RECURSED:
        case MA_OWNED | MA_NOTRECURSED:
                if (!mtx_owned(m))
                        panic("mutex %s not owned at %s:%d",
                            m->lock_object.lo_name, file, line);
                if (mtx_recursed(m)) {
                        if ((what & MA_NOTRECURSED) != 0)
                                panic("mutex %s recursed at %s:%d",
                                    m->lock_object.lo_name, file, line);
                } else if ((what & MA_RECURSED) != 0) {
                        panic("mutex %s unrecursed at %s:%d",
                            m->lock_object.lo_name, file, line);
                }
                break;
        case MA_NOTOWNED:
                if (mtx_owned(m))
                        panic("mutex %s owned at %s:%d",
                            m->lock_object.lo_name, file, line);
                break;
        default:
                panic("unknown mtx_assert at %s:%d", file, line);
        }
}
#endif
 
/*
 * General init routine used by the MTX_SYSINIT() macro.
 */
void
mtx_sysinit(void *arg)
{
        struct mtx_args *margs = arg;
 
        mtx_init((struct mtx *)margs->ma_mtx, margs->ma_desc, NULL,
            margs->ma_opts);
}
 
/*
 * Mutex initialization routine; initialize lock `m' of type contained in
 * `opts' with options contained in `opts' and name `name.'  The optional
 * lock type `type' is used as a general lock category name for use with
 * witness.
 */
void
_mtx_init(volatile uintptr_t *c, const char *name, const char *type, int opts)
{
        struct mtx *m;
        struct lock_class *class;
        int flags;
 
        m = mtxlock2mtx(c);
 
        MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
            MTX_NOWITNESS | MTX_DUPOK | MTX_NOPROFILE | MTX_NEW)) == 0);
        ASSERT_ATOMIC_LOAD_PTR(m->mtx_lock,
            ("%s: mtx_lock not aligned for %s: %p", __func__, name,
            &m->mtx_lock));
 
        /* Determine lock class and lock flags. */
        if (opts & MTX_SPIN)
                class = &lock_class_mtx_spin;
        else
                class = &lock_class_mtx_sleep;
        flags = 0;
        if (opts & MTX_QUIET)
                flags |= LO_QUIET;
        if (opts & MTX_RECURSE)
                flags |= LO_RECURSABLE;
        if ((opts & MTX_NOWITNESS) == 0)
                flags |= LO_WITNESS;
        if (opts & MTX_DUPOK)
                flags |= LO_DUPOK;
        if (opts & MTX_NOPROFILE)
                flags |= LO_NOPROFILE;
        if (opts & MTX_NEW)
                flags |= LO_NEW;
 
        /* Initialize mutex. */
        lock_init(&m->lock_object, class, name, type, flags);
 
        m->mtx_lock = MTX_UNOWNED;
        m->mtx_recurse = 0;
}
 
/*
 * Remove lock `m' from all_mtx queue.  We don't allow MTX_QUIET to be
 * passed in as a flag here because if the corresponding mtx_init() was
 * called with MTX_QUIET set, then it will already be set in the mutex's
 * flags.
 */
void
_mtx_destroy(volatile uintptr_t *c)
{
        struct mtx *m;
 
        m = mtxlock2mtx(c);
 
        if (!mtx_owned(m))
                MPASS(mtx_unowned(m));
        else {
                MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
 
                /* Perform the non-mtx related part of mtx_unlock_spin(). */
                if (LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin) {
                        lock_profile_release_lock(&m->lock_object, true);
                        spinlock_exit();
                } else {
                        TD_LOCKS_DEC(curthread);
                        lock_profile_release_lock(&m->lock_object, false);
                }
 
                /* Tell witness this isn't locked to make it happy. */
                WITNESS_UNLOCK(&m->lock_object, LOP_EXCLUSIVE, __FILE__,
                    __LINE__);
        }
 
        m->mtx_lock = MTX_DESTROYED;
        lock_destroy(&m->lock_object);
}
 
/*
 * Intialize the mutex code and system mutexes.  This is called from the MD
 * startup code prior to mi_startup().  The per-CPU data space needs to be
 * setup before this is called.
 */
void
mutex_init(void)
{
 
        /* Setup turnstiles so that sleep mutexes work. */
        init_turnstiles();
 
        /*
         * Initialize mutexes.
         */
        mtx_init(&Giant, "Giant", NULL, MTX_DEF | MTX_RECURSE);
        mtx_init(&blocked_lock, "blocked lock", NULL, MTX_SPIN);
        blocked_lock.mtx_lock = 0xdeadc0de;     /* Always blocked. */
        mtx_init(&proc0.p_mtx, "process lock", NULL, MTX_DEF | MTX_DUPOK);
        mtx_init(&proc0.p_slock, "process slock", NULL, MTX_SPIN);
        mtx_init(&proc0.p_statmtx, "pstatl", NULL, MTX_SPIN);
        mtx_init(&proc0.p_itimmtx, "pitiml", NULL, MTX_SPIN);
        mtx_init(&proc0.p_profmtx, "pprofl", NULL, MTX_SPIN);
        mtx_init(&devmtx, "cdev", NULL, MTX_DEF);
        mtx_lock(&Giant);
}
 
static void __noinline
_mtx_lock_indefinite_check(struct mtx *m, struct lock_delay_arg *ldap)
{
        struct thread *td;
 
        ldap->spin_cnt++;
        if (ldap->spin_cnt < 60000000 || kdb_active || KERNEL_PANICKED())
                cpu_lock_delay();
        else {
                td = mtx_owner(m);
 
                /* If the mutex is unlocked, try again. */
                if (td == NULL)
                        return;
 
                printf( "spin lock %p (%s) held by %p (tid %d) too long\n",
                    m, m->lock_object.lo_name, td, td->td_tid);
#ifdef WITNESS
                witness_display_spinlock(&m->lock_object, td, printf);
#endif
                panic("spin lock held too long");
        }
        cpu_spinwait();
}
 
void
mtx_spin_wait_unlocked(struct mtx *m)
{
        struct lock_delay_arg lda;
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("%s() of destroyed mutex %p", __func__, m));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_spin,
            ("%s() of sleep mutex %p (%s)", __func__, m,
            m->lock_object.lo_name));
        KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m,
            m->lock_object.lo_name));
 
        lda.spin_cnt = 0;
 
        while (atomic_load_acq_ptr(&m->mtx_lock) != MTX_UNOWNED) {
                if (__predict_true(lda.spin_cnt < 10000000)) {
                        cpu_spinwait();
                        lda.spin_cnt++;
                } else {
                        _mtx_lock_indefinite_check(m, &lda);
                }
        }
}
 
void
mtx_wait_unlocked(struct mtx *m)
{
        struct thread *owner;
        uintptr_t v;
 
        KASSERT(m->mtx_lock != MTX_DESTROYED,
            ("%s() of destroyed mutex %p", __func__, m));
        KASSERT(LOCK_CLASS(&m->lock_object) == &lock_class_mtx_sleep,
            ("%s() not a sleep mutex %p (%s)", __func__, m,
            m->lock_object.lo_name));
        KASSERT(!mtx_owned(m), ("%s() waiting on myself on lock %p (%s)", __func__, m,
            m->lock_object.lo_name));
 
        for (;;) {
                v = atomic_load_acq_ptr(&m->mtx_lock);
                if (v == MTX_UNOWNED) {
                        break;
                }
                owner = lv_mtx_owner(v);
                if (!TD_IS_RUNNING(owner)) {
                        mtx_lock(m);
                        mtx_unlock(m);
                        break;
                }
                cpu_spinwait();
        }
}
 
#ifdef DDB
void
db_show_mtx(const struct lock_object *lock)
{
        struct thread *td;
        const struct mtx *m;
 
        m = (const struct mtx *)lock;
 
        db_printf(" flags: {");
        if (LOCK_CLASS(lock) == &lock_class_mtx_spin)
                db_printf("SPIN");
        else
                db_printf("DEF");
        if (m->lock_object.lo_flags & LO_RECURSABLE)
                db_printf(", RECURSE");
        if (m->lock_object.lo_flags & LO_DUPOK)
                db_printf(", DUPOK");
        db_printf("}\n");
        db_printf(" state: {");
        if (mtx_unowned(m))
                db_printf("UNOWNED");
        else if (mtx_destroyed(m))
                db_printf("DESTROYED");
        else {
                db_printf("OWNED");
                if (m->mtx_lock & MTX_CONTESTED)
                        db_printf(", CONTESTED");
                if (m->mtx_lock & MTX_RECURSED)
                        db_printf(", RECURSED");
        }
        db_printf("}\n");
        if (!mtx_unowned(m) && !mtx_destroyed(m)) {
                td = mtx_owner(m);
                db_printf(" owner: %p (tid %d, pid %d, \"%s\")\n", td,
                    td->td_tid, td->td_proc->p_pid, td->td_name);
                if (mtx_recursed(m))
                        db_printf(" recursed: %d\n", m->mtx_recurse);
        }
}
#endif