734 lines
19 KiB
C
734 lines
19 KiB
C
/*-
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* Copyright (c) 1998 Berkeley Software Design, Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Berkeley Software Design Inc's name may not be used to endorse or
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* promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* from BSDI $Id: mutex_witness.c,v 1.1.2.20 2000/04/27 03:10:27 cp Exp $
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* and BSDI $Id: synch_machdep.c,v 2.3.2.39 2000/04/27 03:10:25 cp Exp $
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* $FreeBSD$
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*/
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/*
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* Machine independent bits of mutex implementation.
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*/
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#include "opt_ddb.h"
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#include <sys/param.h>
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#include <sys/bus.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/resourcevar.h>
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#include <sys/sysctl.h>
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#include <sys/systm.h>
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#include <sys/vmmeter.h>
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#include <sys/ktr.h>
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#include <machine/atomic.h>
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#include <machine/bus.h>
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#include <machine/clock.h>
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#include <machine/cpu.h>
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#include <ddb/ddb.h>
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#include <vm/vm.h>
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#include <vm/vm_extern.h>
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/*
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* Internal utility macros.
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*/
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#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
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#define mtx_owner(m) (mtx_unowned((m)) ? NULL \
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: (struct thread *)((m)->mtx_lock & MTX_FLAGMASK))
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#define SET_PRIO(td, pri) (td)->td_ksegrp->kg_pri.pri_level = (pri)
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/*
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* Lock classes for sleep and spin mutexes.
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*/
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struct lock_class lock_class_mtx_sleep = {
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"sleep mutex",
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LC_SLEEPLOCK | LC_RECURSABLE
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};
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struct lock_class lock_class_mtx_spin = {
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"spin mutex",
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LC_SPINLOCK | LC_RECURSABLE
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};
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/*
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* Prototypes for non-exported routines.
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*/
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static void propagate_priority(struct thread *);
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static void
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propagate_priority(struct thread *td)
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{
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struct ksegrp *kg = td->td_ksegrp;
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int pri = kg->kg_pri.pri_level;
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struct mtx *m = td->td_blocked;
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mtx_assert(&sched_lock, MA_OWNED);
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for (;;) {
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struct thread *td1;
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td = mtx_owner(m);
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if (td == NULL) {
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/*
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* This really isn't quite right. Really
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* ought to bump priority of thread that
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* next acquires the mutex.
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*/
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MPASS(m->mtx_lock == MTX_CONTESTED);
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return;
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}
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kg = td->td_ksegrp;
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MPASS(td->td_proc->p_magic == P_MAGIC);
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KASSERT(td->td_proc->p_stat != SSLEEP, ("sleeping thread owns a mutex"));
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if (kg->kg_pri.pri_level <= pri) /* lower is higher priority */
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return;
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/*
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* Bump this thread's priority.
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*/
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SET_PRIO(td, pri);
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/*
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* If lock holder is actually running, just bump priority.
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*/
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/* XXXKSE this test is not sufficient */
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if (td->td_kse && (td->td_kse->ke_oncpu != NOCPU)) {
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MPASS(td->td_proc->p_stat == SRUN
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|| td->td_proc->p_stat == SZOMB
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|| td->td_proc->p_stat == SSTOP);
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return;
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}
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#ifndef SMP
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/*
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* For UP, we check to see if td is curthread (this shouldn't
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* ever happen however as it would mean we are in a deadlock.)
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*/
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KASSERT(td != curthread, ("Deadlock detected"));
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#endif
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/*
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* If on run queue move to new run queue, and quit.
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* XXXKSE this gets a lot more complicated under threads
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* but try anyhow.
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*/
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if (td->td_proc->p_stat == SRUN) {
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MPASS(td->td_blocked == NULL);
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remrunqueue(td);
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setrunqueue(td);
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return;
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}
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/*
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* If we aren't blocked on a mutex, we should be.
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*/
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KASSERT(td->td_proc->p_stat == SMTX, (
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"process %d(%s):%d holds %s but isn't blocked on a mutex\n",
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td->td_proc->p_pid, td->td_proc->p_comm, td->td_proc->p_stat,
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m->mtx_object.lo_name));
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/*
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* Pick up the mutex that td is blocked on.
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*/
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m = td->td_blocked;
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MPASS(m != NULL);
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/*
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* Check if the thread needs to be moved up on
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* the blocked chain
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*/
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if (td == TAILQ_FIRST(&m->mtx_blocked)) {
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continue;
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}
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td1 = TAILQ_PREV(td, threadqueue, td_blkq);
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if (td1->td_ksegrp->kg_pri.pri_level <= pri) {
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continue;
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}
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/*
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* Remove thread from blocked chain and determine where
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* it should be moved up to. Since we know that td1 has
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* a lower priority than td, we know that at least one
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* thread in the chain has a lower priority and that
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* td1 will thus not be NULL after the loop.
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*/
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TAILQ_REMOVE(&m->mtx_blocked, td, td_blkq);
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TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq) {
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MPASS(td1->td_proc->p_magic == P_MAGIC);
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if (td1->td_ksegrp->kg_pri.pri_level > pri)
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break;
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}
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MPASS(td1 != NULL);
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TAILQ_INSERT_BEFORE(td1, td, td_blkq);
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CTR4(KTR_LOCK,
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"propagate_priority: p %p moved before %p on [%p] %s",
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td, td1, m, m->mtx_object.lo_name);
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}
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}
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/*
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* Function versions of the inlined __mtx_* macros. These are used by
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* modules and can also be called from assembly language if needed.
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*/
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void
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_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
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{
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MPASS(curthread != NULL);
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_get_sleep_lock(m, curthread, opts, file, line);
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LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
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line);
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WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
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}
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void
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_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
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{
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MPASS(curthread != NULL);
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mtx_assert(m, MA_OWNED);
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WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
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LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
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line);
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_rel_sleep_lock(m, curthread, opts, file, line);
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}
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void
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_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
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{
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MPASS(curthread != NULL);
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_get_spin_lock(m, curthread, opts, file, line);
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LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
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line);
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WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
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}
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void
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_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
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{
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MPASS(curthread != NULL);
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mtx_assert(m, MA_OWNED);
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WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
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LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
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line);
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_rel_spin_lock(m);
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}
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/*
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* The important part of mtx_trylock{,_flags}()
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* Tries to acquire lock `m.' We do NOT handle recursion here; we assume that
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* if we're called, it's because we know we don't already own this lock.
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*/
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int
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_mtx_trylock(struct mtx *m, int opts, const char *file, int line)
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{
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int rval;
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MPASS(curthread != NULL);
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rval = _obtain_lock(m, curthread);
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LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line);
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if (rval) {
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/*
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* We do not handle recursion in _mtx_trylock; see the
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* note at the top of the routine.
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*/
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KASSERT(!mtx_recursed(m),
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("mtx_trylock() called on a recursed mutex"));
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WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
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file, line);
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}
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return (rval);
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}
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/*
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* _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
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*
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* We call this if the lock is either contested (i.e. we need to go to
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* sleep waiting for it), or if we need to recurse on it.
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*/
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void
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_mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
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{
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struct thread *td = curthread;
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struct ksegrp *kg = td->td_ksegrp;
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if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) {
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m->mtx_recurse++;
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atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
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return;
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}
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR4(KTR_LOCK,
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"_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
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m->mtx_object.lo_name, (void *)m->mtx_lock, file, line);
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while (!_obtain_lock(m, td)) {
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uintptr_t v;
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struct thread *td1;
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mtx_lock_spin(&sched_lock);
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/*
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* Check if the lock has been released while spinning for
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* the sched_lock.
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*/
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if ((v = m->mtx_lock) == MTX_UNOWNED) {
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mtx_unlock_spin(&sched_lock);
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continue;
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}
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/*
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* The mutex was marked contested on release. This means that
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* there are threads blocked on it.
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*/
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if (v == MTX_CONTESTED) {
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td1 = TAILQ_FIRST(&m->mtx_blocked);
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MPASS(td1 != NULL);
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m->mtx_lock = (uintptr_t)td | MTX_CONTESTED;
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if (td1->td_ksegrp->kg_pri.pri_level < kg->kg_pri.pri_level)
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SET_PRIO(td, td1->td_ksegrp->kg_pri.pri_level);
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mtx_unlock_spin(&sched_lock);
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return;
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}
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/*
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* If the mutex isn't already contested and a failure occurs
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* setting the contested bit, the mutex was either released
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* or the state of the MTX_RECURSED bit changed.
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*/
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if ((v & MTX_CONTESTED) == 0 &&
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!atomic_cmpset_ptr(&m->mtx_lock, (void *)v,
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(void *)(v | MTX_CONTESTED))) {
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mtx_unlock_spin(&sched_lock);
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continue;
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}
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/*
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* We deffinately must sleep for this lock.
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*/
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mtx_assert(m, MA_NOTOWNED);
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#ifdef notyet
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/*
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* If we're borrowing an interrupted thread's VM context, we
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* must clean up before going to sleep.
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*/
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if (td->td_ithd != NULL) {
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struct ithd *it = td->td_ithd;
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if (it->it_interrupted) {
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR2(KTR_LOCK,
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"_mtx_lock_sleep: %p interrupted %p",
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it, it->it_interrupted);
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intr_thd_fixup(it);
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}
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}
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#endif
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/*
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* Put us on the list of threads blocked on this mutex.
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*/
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if (TAILQ_EMPTY(&m->mtx_blocked)) {
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td1 = mtx_owner(m);
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LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested);
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TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq);
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} else {
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TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq)
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if (td1->td_ksegrp->kg_pri.pri_level > kg->kg_pri.pri_level)
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break;
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if (td1)
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TAILQ_INSERT_BEFORE(td1, td, td_blkq);
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else
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TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq);
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}
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/*
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* Save who we're blocked on.
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*/
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td->td_blocked = m;
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td->td_mtxname = m->mtx_object.lo_name;
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td->td_proc->p_stat = SMTX;
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propagate_priority(td);
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR3(KTR_LOCK,
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"_mtx_lock_sleep: p %p blocked on [%p] %s", td, m,
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m->mtx_object.lo_name);
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td->td_proc->p_stats->p_ru.ru_nvcsw++;
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mi_switch();
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR3(KTR_LOCK,
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"_mtx_lock_sleep: p %p free from blocked on [%p] %s",
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td, m, m->mtx_object.lo_name);
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mtx_unlock_spin(&sched_lock);
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}
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return;
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}
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/*
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* _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
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*
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* This is only called if we need to actually spin for the lock. Recursion
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* is handled inline.
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*/
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void
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_mtx_lock_spin(struct mtx *m, int opts, const char *file, int line)
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{
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int i = 0;
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
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for (;;) {
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if (_obtain_lock(m, curthread))
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break;
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/* Give interrupts a chance while we spin. */
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critical_exit();
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while (m->mtx_lock != MTX_UNOWNED) {
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if (i++ < 10000000)
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continue;
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if (i++ < 60000000)
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DELAY(1);
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#ifdef DDB
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else if (!db_active)
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#else
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else
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#endif
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panic("spin lock %s held by %p for > 5 seconds",
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m->mtx_object.lo_name, (void *)m->mtx_lock);
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}
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critical_enter();
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}
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
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return;
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}
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|
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/*
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* _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
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*
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* We are only called here if the lock is recursed or contested (i.e. we
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* need to wake up a blocked thread).
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*/
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void
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_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
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{
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struct thread *td, *td1;
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struct mtx *m1;
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int pri;
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struct ksegrp *kg;
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td = curthread;
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kg = td->td_ksegrp;
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if (mtx_recursed(m)) {
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if (--(m->mtx_recurse) == 0)
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atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
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return;
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}
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mtx_lock_spin(&sched_lock);
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
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CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
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td1 = TAILQ_FIRST(&m->mtx_blocked);
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MPASS(td->td_proc->p_magic == P_MAGIC);
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MPASS(td1->td_proc->p_magic == P_MAGIC);
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TAILQ_REMOVE(&m->mtx_blocked, td1, td_blkq);
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if (TAILQ_EMPTY(&m->mtx_blocked)) {
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LIST_REMOVE(m, mtx_contested);
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_release_lock_quick(m);
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if (LOCK_LOG_TEST(&m->mtx_object, opts))
|
|
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m);
|
|
} else
|
|
atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED);
|
|
|
|
pri = PRI_MAX;
|
|
LIST_FOREACH(m1, &td->td_contested, mtx_contested) {
|
|
int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_ksegrp->kg_pri.pri_level;
|
|
if (cp < pri)
|
|
pri = cp;
|
|
}
|
|
|
|
if (pri > kg->kg_pri.pri_native)
|
|
pri = kg->kg_pri.pri_native;
|
|
SET_PRIO(td, pri);
|
|
|
|
if (LOCK_LOG_TEST(&m->mtx_object, opts))
|
|
CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p",
|
|
m, td1);
|
|
|
|
td1->td_blocked = NULL;
|
|
td1->td_proc->p_stat = SRUN;
|
|
setrunqueue(td1);
|
|
|
|
if (td->td_critnest == 1 && td1->td_ksegrp->kg_pri.pri_level < pri) {
|
|
#ifdef notyet
|
|
if (td->td_ithd != NULL) {
|
|
struct ithd *it = td->td_ithd;
|
|
|
|
if (it->it_interrupted) {
|
|
if (LOCK_LOG_TEST(&m->mtx_object, opts))
|
|
CTR2(KTR_LOCK,
|
|
"_mtx_unlock_sleep: %p interrupted %p",
|
|
it, it->it_interrupted);
|
|
intr_thd_fixup(it);
|
|
}
|
|
}
|
|
#endif
|
|
setrunqueue(td);
|
|
if (LOCK_LOG_TEST(&m->mtx_object, opts))
|
|
CTR2(KTR_LOCK,
|
|
"_mtx_unlock_sleep: %p switching out lock=%p", m,
|
|
(void *)m->mtx_lock);
|
|
|
|
td->td_proc->p_stats->p_ru.ru_nivcsw++;
|
|
mi_switch();
|
|
if (LOCK_LOG_TEST(&m->mtx_object, opts))
|
|
CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p",
|
|
m, (void *)m->mtx_lock);
|
|
}
|
|
|
|
mtx_unlock_spin(&sched_lock);
|
|
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* All the unlocking of MTX_SPIN locks is done inline.
|
|
* See the _rel_spin_lock() macro for the details.
|
|
*/
|
|
|
|
/*
|
|
* The backing function for the INVARIANTS-enabled mtx_assert()
|
|
*/
|
|
#ifdef INVARIANT_SUPPORT
|
|
void
|
|
_mtx_assert(struct mtx *m, int what, const char *file, int line)
|
|
{
|
|
|
|
if (panicstr != NULL)
|
|
return;
|
|
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->mtx_object.lo_name, file, line);
|
|
if (mtx_recursed(m)) {
|
|
if ((what & MA_NOTRECURSED) != 0)
|
|
panic("mutex %s recursed at %s:%d",
|
|
m->mtx_object.lo_name, file, line);
|
|
} else if ((what & MA_RECURSED) != 0) {
|
|
panic("mutex %s unrecursed at %s:%d",
|
|
m->mtx_object.lo_name, file, line);
|
|
}
|
|
break;
|
|
case MA_NOTOWNED:
|
|
if (mtx_owned(m))
|
|
panic("mutex %s owned at %s:%d",
|
|
m->mtx_object.lo_name, file, line);
|
|
break;
|
|
default:
|
|
panic("unknown mtx_assert at %s:%d", file, line);
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* The MUTEX_DEBUG-enabled mtx_validate()
|
|
*
|
|
* Most of these checks have been moved off into the LO_INITIALIZED flag
|
|
* maintained by the witness code.
|
|
*/
|
|
#ifdef MUTEX_DEBUG
|
|
|
|
void mtx_validate __P((struct mtx *));
|
|
|
|
void
|
|
mtx_validate(struct mtx *m)
|
|
{
|
|
|
|
/*
|
|
* XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly
|
|
* we can re-enable the kernacc() checks.
|
|
*/
|
|
#ifndef __alpha__
|
|
/*
|
|
* Can't call kernacc() from early init386(), especially when
|
|
* initializing Giant mutex, because some stuff in kernacc()
|
|
* requires Giant itself.
|
|
*/
|
|
if (!cold)
|
|
if (!kernacc((caddr_t)m, sizeof(m),
|
|
VM_PROT_READ | VM_PROT_WRITE))
|
|
panic("Can't read and write to mutex %p", m);
|
|
#endif
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Mutex initialization routine; initialize lock `m' of type contained in
|
|
* `opts' with options contained in `opts' and description `description.'
|
|
*/
|
|
void
|
|
mtx_init(struct mtx *m, const char *description, int opts)
|
|
{
|
|
struct lock_object *lock;
|
|
|
|
MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
|
|
MTX_SLEEPABLE | MTX_NOWITNESS)) == 0);
|
|
|
|
#ifdef MUTEX_DEBUG
|
|
/* Diagnostic and error correction */
|
|
mtx_validate(m);
|
|
#endif
|
|
|
|
lock = &m->mtx_object;
|
|
KASSERT((lock->lo_flags & LO_INITIALIZED) == 0,
|
|
("mutex %s %p already initialized", description, m));
|
|
bzero(m, sizeof(*m));
|
|
if (opts & MTX_SPIN)
|
|
lock->lo_class = &lock_class_mtx_spin;
|
|
else
|
|
lock->lo_class = &lock_class_mtx_sleep;
|
|
lock->lo_name = description;
|
|
if (opts & MTX_QUIET)
|
|
lock->lo_flags = LO_QUIET;
|
|
if (opts & MTX_RECURSE)
|
|
lock->lo_flags |= LO_RECURSABLE;
|
|
if (opts & MTX_SLEEPABLE)
|
|
lock->lo_flags |= LO_SLEEPABLE;
|
|
if ((opts & MTX_NOWITNESS) == 0)
|
|
lock->lo_flags |= LO_WITNESS;
|
|
|
|
m->mtx_lock = MTX_UNOWNED;
|
|
TAILQ_INIT(&m->mtx_blocked);
|
|
|
|
LOCK_LOG_INIT(lock, opts);
|
|
|
|
WITNESS_INIT(lock);
|
|
}
|
|
|
|
/*
|
|
* 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(struct mtx *m)
|
|
{
|
|
|
|
LOCK_LOG_DESTROY(&m->mtx_object, 0);
|
|
|
|
if (!mtx_owned(m))
|
|
MPASS(mtx_unowned(m));
|
|
else {
|
|
MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
|
|
|
|
/* Tell witness this isn't locked to make it happy. */
|
|
WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE, __FILE__,
|
|
__LINE__);
|
|
}
|
|
|
|
WITNESS_DESTROY(&m->mtx_object);
|
|
}
|
|
|
|
/*
|
|
* Encapsulated Giant mutex routines. These routines provide encapsulation
|
|
* control for the Giant mutex, allowing sysctls to be used to turn on and
|
|
* off Giant around certain subsystems. The default value for the sysctls
|
|
* are set to what developers believe is stable and working in regards to
|
|
* the Giant pushdown. Developers should not turn off Giant via these
|
|
* sysctls unless they know what they are doing.
|
|
*
|
|
* Callers of mtx_lock_giant() are expected to pass the return value to an
|
|
* accompanying mtx_unlock_giant() later on. If multiple subsystems are
|
|
* effected by a Giant wrap, all related sysctl variables must be zero for
|
|
* the subsystem call to operate without Giant (as determined by the caller).
|
|
*/
|
|
|
|
SYSCTL_NODE(_kern, OID_AUTO, giant, CTLFLAG_RD, NULL, "Giant mutex manipulation");
|
|
|
|
static int kern_giant_all = 0;
|
|
SYSCTL_INT(_kern_giant, OID_AUTO, all, CTLFLAG_RW, &kern_giant_all, 0, "");
|
|
|
|
int kern_giant_proc = 1; /* Giant around PROC locks */
|
|
int kern_giant_file = 1; /* Giant around struct file & filedesc */
|
|
SYSCTL_INT(_kern_giant, OID_AUTO, proc, CTLFLAG_RW, &kern_giant_proc, 0, "");
|
|
SYSCTL_INT(_kern_giant, OID_AUTO, file, CTLFLAG_RW, &kern_giant_file, 0, "");
|
|
|
|
int
|
|
mtx_lock_giant(int sysctlvar)
|
|
{
|
|
if (sysctlvar || kern_giant_all) {
|
|
mtx_lock(&Giant);
|
|
return(1);
|
|
}
|
|
return(0);
|
|
}
|
|
|
|
void
|
|
mtx_unlock_giant(int s)
|
|
{
|
|
if (s)
|
|
mtx_unlock(&Giant);
|
|
}
|
|
|