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f404050e44
freebsd-nq/sys/kern/kern_mutex.c
John Baldwin f404050e44 Use an atomic operation with an appropriate memory barrier when releasing 
a contested sleep mutex in the case that at least two processes are blocked
on the contested mutex.
2000-11-29 18:41:19 +00:00

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/*-
* 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 $
* $FreeBSD$
*/
/*
* Main Entry: witness
* Pronunciation: 'wit-n&s
* Function: noun
* Etymology: Middle English witnesse, from Old English witnes knowledge,
* testimony, witness, from 2wit
* Date: before 12th century
* 1 : attestation of a fact or event : TESTIMONY
* 2 : one that gives evidence; specifically : one who testifies in
* a cause or before a judicial tribunal
* 3 : one asked to be present at a transaction so as to be able to
* testify to its having taken place
* 4 : one who has personal knowledge of something
* 5 a : something serving as evidence or proof : SIGN
* b : public affirmation by word or example of usually
* religious faith or conviction <the heroic witness to divine
* life -- Pilot>
* 6 capitalized : a member of the Jehovah's Witnesses
*/
#include "opt_ddb.h"
#include "opt_witness.h"
/*
* Cause non-inlined mtx_*() to be compiled.
* Must be defined early because other system headers may include mutex.h.
*/
#define _KERN_MUTEX_C_
#include <sys/param.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/systm.h>
#include <sys/vmmeter.h>
#include <sys/ktr.h>
#include <machine/atomic.h>
#include <machine/bus.h>
#include <machine/clock.h>
#include <machine/cpu.h>
#include <ddb/ddb.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <sys/mutex.h>
/*
* Machine independent bits of the mutex implementation
*/
/* All mutexes in system (used for debug/panic) */
#ifdef MUTEX_DEBUG
static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0,
"All mutexes queue head" };
static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, &all_mtx_debug,
TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
{ NULL, NULL }, &all_mtx, &all_mtx };
#else /* MUTEX_DEBUG */
static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, "All mutexes queue head",
TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
{ NULL, NULL }, &all_mtx, &all_mtx };
#endif /* MUTEX_DEBUG */
static int mtx_cur_cnt;
static int mtx_max_cnt;
void _mtx_enter_giant_def(void);
void _mtx_exit_giant_def(void);
static void propagate_priority(struct proc *) __unused;
#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
#define mtx_owner(m) (mtx_unowned(m) ? NULL \
: (struct proc *)((m)->mtx_lock & MTX_FLAGMASK))
#define RETIP(x) *(((uintptr_t *)(&x)) - 1)
#define SET_PRIO(p, pri) (p)->p_priority = (pri)
/*
* XXX Temporary, for use from assembly language
*/
void
_mtx_enter_giant_def(void)
{
mtx_enter(&Giant, MTX_DEF);
}
void
_mtx_exit_giant_def(void)
{
mtx_exit(&Giant, MTX_DEF);
}
static void
propagate_priority(struct proc *p)
{
int pri = p->p_priority;
struct mtx *m = p->p_blocked;
for (;;) {
struct proc *p1;
p = mtx_owner(m);
if (p == NULL) {
/*
* This really isn't quite right. Really
* ought to bump priority of process that
* next acquires the mutex.
*/
MPASS(m->mtx_lock == MTX_CONTESTED);
return;
}
MPASS(p->p_magic == P_MAGIC);
if (p->p_priority <= pri)
return;
/*
* If lock holder is actually running, just bump priority.
*/
if (TAILQ_NEXT(p, p_procq) == NULL) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
SET_PRIO(p, pri);
return;
}
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
MPASS(p->p_blocked == NULL);
remrunqueue(p);
SET_PRIO(p, pri);
setrunqueue(p);
return;
}
/*
* If we aren't blocked on a mutex, give up and quit.
*/
if (p->p_stat != SMTX) {
printf(
"XXX: process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat, m->mtx_description);
return;
}
/*
* Pick up the mutex that p is blocked on.
*/
m = p->p_blocked;
MPASS(m != NULL);
printf("XXX: process %d(%s) is blocked on %s\n", p->p_pid,
p->p_comm, m->mtx_description);
/*
* Check if the proc needs to be moved up on
* the blocked chain
*/
if ((p1 = TAILQ_PREV(p, rq, p_procq)) == NULL ||
p1->p_priority <= pri) {
if (p1)
printf(
"XXX: previous process %d(%s) has higher priority\n",
p->p_pid, p->p_comm);
else
printf("XXX: process at head of run queue\n");
continue;
}
/*
* Remove proc from blocked chain
*/
TAILQ_REMOVE(&m->mtx_blocked, p, p_procq);
TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) {
MPASS(p1->p_magic == P_MAGIC);
if (p1->p_priority > pri)
break;
}
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
CTR4(KTR_LOCK,
"propagate priority: p 0x%p moved before 0x%p on [0x%p] %s",
p, p1, m, m->mtx_description);
}
}
void
mtx_enter_hard(struct mtx *m, int type, int saveintr)
{
struct proc *p = CURPROC;
KASSERT(p != NULL, ("curproc is NULL in mutex"));
switch (type) {
case MTX_DEF:
if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)p) {
m->mtx_recurse++;
atomic_set_ptr(&m->mtx_lock, MTX_RECURSE);
CTR1(KTR_LOCK, "mtx_enter: 0x%p recurse", m);
return;
}
CTR3(KTR_LOCK, "mtx_enter: 0x%p contested (lock=%p) [0x%p]",
m, (void *)m->mtx_lock, (void *)RETIP(m));
while (!_obtain_lock(m, p)) {
uintptr_t v;
struct proc *p1;
mtx_enter(&sched_lock, MTX_SPIN | MTX_RLIKELY);
/*
* check if the lock has been released while
* waiting for the schedlock.
*/
if ((v = m->mtx_lock) == MTX_UNOWNED) {
mtx_exit(&sched_lock, MTX_SPIN);
continue;
}
/*
* The mutex was marked contested on release. This
* means that there are processes blocked on it.
*/
if (v == MTX_CONTESTED) {
p1 = TAILQ_FIRST(&m->mtx_blocked);
KASSERT(p1 != NULL, ("contested mutex has no contesters"));
KASSERT(p != NULL, ("curproc is NULL for contested mutex"));
m->mtx_lock = (uintptr_t)p | MTX_CONTESTED;
if (p1->p_priority < p->p_priority) {
SET_PRIO(p, p1->p_priority);
}
mtx_exit(&sched_lock, MTX_SPIN);
return;
}
/*
* If the mutex isn't already contested and
* a failure occurs setting the contested bit the
* mutex was either release or the
* state of the RECURSION bit changed.
*/
if ((v & MTX_CONTESTED) == 0 &&
!atomic_cmpset_ptr(&m->mtx_lock, (void *)v,
(void *)(v | MTX_CONTESTED))) {
mtx_exit(&sched_lock, MTX_SPIN);
continue;
}
/* We definitely have to sleep for this lock */
mtx_assert(m, MA_NOTOWNED);
#ifdef notyet
/*
* If we're borrowing an interrupted thread's VM
* context must clean up before going to sleep.
*/
if (p->p_flag & (P_ITHD | P_SITHD)) {
ithd_t *it = (ithd_t *)p;
if (it->it_interrupted) {
CTR2(KTR_LOCK,
"mtx_enter: 0x%x interrupted 0x%x",
it, it->it_interrupted);
intr_thd_fixup(it);
}
}
#endif
/* Put us on the list of procs blocked on this mutex */
if (TAILQ_EMPTY(&m->mtx_blocked)) {
p1 = (struct proc *)(m->mtx_lock &
MTX_FLAGMASK);
LIST_INSERT_HEAD(&p1->p_contested, m,
mtx_contested);
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
} else {
TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq)
if (p1->p_priority > p->p_priority)
break;
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p,
p_procq);
}
p->p_blocked = m; /* Who we're blocked on */
p->p_stat = SMTX;
#if 0
propagate_priority(p);
#endif
CTR3(KTR_LOCK, "mtx_enter: p 0x%p blocked on [0x%p] %s",
p, m, m->mtx_description);
mi_switch();
CTR3(KTR_LOCK,
"mtx_enter: p 0x%p free from blocked on [0x%p] %s",
p, m, m->mtx_description);
mtx_exit(&sched_lock, MTX_SPIN);
}
return;
case MTX_SPIN:
case MTX_SPIN | MTX_FIRST:
case MTX_SPIN | MTX_TOPHALF:
{
int i = 0;
if (m->mtx_lock == (uintptr_t)p) {
m->mtx_recurse++;
return;
}
CTR1(KTR_LOCK, "mtx_enter: %p spinning", m);
for (;;) {
if (_obtain_lock(m, p))
break;
while (m->mtx_lock != MTX_UNOWNED) {
if (i++ < 1000000)
continue;
if (i++ < 6000000)
DELAY (1);
#ifdef DDB
else if (!db_active)
#else
else
#endif
panic(
"spin lock %s held by 0x%p for > 5 seconds",
m->mtx_description,
(void *)m->mtx_lock);
}
}
#ifdef MUTEX_DEBUG
if (type != MTX_SPIN)
m->mtx_saveintr = 0xbeefface;
else
#endif
m->mtx_saveintr = saveintr;
CTR1(KTR_LOCK, "mtx_enter: 0x%p spin done", m);
return;
}
}
}
void
mtx_exit_hard(struct mtx *m, int type)
{
struct proc *p, *p1;
struct mtx *m1;
int pri;
p = CURPROC;
switch (type) {
case MTX_DEF:
case MTX_DEF | MTX_NOSWITCH:
if (m->mtx_recurse != 0) {
if (--(m->mtx_recurse) == 0)
atomic_clear_ptr(&m->mtx_lock, MTX_RECURSE);
CTR1(KTR_LOCK, "mtx_exit: 0x%p unrecurse", m);
return;
}
mtx_enter(&sched_lock, MTX_SPIN);
CTR1(KTR_LOCK, "mtx_exit: 0x%p contested", m);
p1 = TAILQ_FIRST(&m->mtx_blocked);
MPASS(p->p_magic == P_MAGIC);
MPASS(p1->p_magic == P_MAGIC);
TAILQ_REMOVE(&m->mtx_blocked, p1, p_procq);
if (TAILQ_EMPTY(&m->mtx_blocked)) {
LIST_REMOVE(m, mtx_contested);
_release_lock_quick(m);
CTR1(KTR_LOCK, "mtx_exit: 0x%p not held", m);
} else
atomic_store_rel_ptr(&m->mtx_lock,
(void *)MTX_CONTESTED);
pri = MAXPRI;
LIST_FOREACH(m1, &p->p_contested, mtx_contested) {
int cp = TAILQ_FIRST(&m1->mtx_blocked)->p_priority;
if (cp < pri)
pri = cp;
}
if (pri > p->p_nativepri)
pri = p->p_nativepri;
SET_PRIO(p, pri);
CTR2(KTR_LOCK, "mtx_exit: 0x%p contested setrunqueue 0x%p",
m, p1);
p1->p_blocked = NULL;
p1->p_stat = SRUN;
setrunqueue(p1);
if ((type & MTX_NOSWITCH) == 0 && p1->p_priority < pri) {
#ifdef notyet
if (p->p_flag & (P_ITHD | P_SITHD)) {
ithd_t *it = (ithd_t *)p;
if (it->it_interrupted) {
CTR2(KTR_LOCK,
"mtx_exit: 0x%x interruped 0x%x",
it, it->it_interrupted);
intr_thd_fixup(it);
}
}
#endif
setrunqueue(p);
CTR2(KTR_LOCK, "mtx_exit: 0x%p switching out lock=0x%p",
m, (void *)m->mtx_lock);
mi_switch();
CTR2(KTR_LOCK, "mtx_exit: 0x%p resuming lock=0x%p",
m, (void *)m->mtx_lock);
}
mtx_exit(&sched_lock, MTX_SPIN);
break;
case MTX_SPIN:
case MTX_SPIN | MTX_FIRST:
if (m->mtx_recurse != 0) {
m->mtx_recurse--;
return;
}
MPASS(mtx_owned(m));
_release_lock_quick(m);
if (type & MTX_FIRST)
enable_intr(); /* XXX is this kosher? */
else {
MPASS(m->mtx_saveintr != 0xbeefface);
restore_intr(m->mtx_saveintr);
}
break;
case MTX_SPIN | MTX_TOPHALF:
if (m->mtx_recurse != 0) {
m->mtx_recurse--;
return;
}
MPASS(mtx_owned(m));
_release_lock_quick(m);
break;
default:
panic("mtx_exit_hard: unsupported type 0x%x\n", type);
}
}
#define MV_DESTROY 0 /* validate before destory */
#define MV_INIT 1 /* validate before init */
#ifdef MUTEX_DEBUG
int mtx_validate __P((struct mtx *, int));
int
mtx_validate(struct mtx *m, int when)
{
struct mtx *mp;
int i;
int retval = 0;
if (m == &all_mtx || cold)
return 0;
mtx_enter(&all_mtx, MTX_DEF);
/*
* XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly
* we can re-enable the kernacc() checks.
*/
#ifndef __alpha__
MPASS(kernacc((caddr_t)all_mtx.mtx_next, sizeof(uintptr_t),
VM_PROT_READ) == 1);
#endif
MPASS(all_mtx.mtx_next->mtx_prev == &all_mtx);
for (i = 0, mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) {
#ifndef __alpha__
if (kernacc((caddr_t)mp->mtx_next, sizeof(uintptr_t),
VM_PROT_READ) != 1) {
panic("mtx_validate: mp=%p mp->mtx_next=%p",
mp, mp->mtx_next);
}
#endif
i++;
if (i > mtx_cur_cnt) {
panic("mtx_validate: too many in chain, known=%d\n",
mtx_cur_cnt);
}
}
MPASS(i == mtx_cur_cnt);
switch (when) {
case MV_DESTROY:
for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next)
if (mp == m)
break;
MPASS(mp == m);
break;
case MV_INIT:
for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next)
if (mp == m) {
/*
* Not good. This mutex already exists.
*/
printf("re-initing existing mutex %s\n",
m->mtx_description);
MPASS(m->mtx_lock == MTX_UNOWNED);
retval = 1;
}
}
mtx_exit(&all_mtx, MTX_DEF);
return (retval);
}
#endif
void
mtx_init(struct mtx *m, const char *t, int flag)
{
#ifdef MUTEX_DEBUG
struct mtx_debug *debug;
#endif
CTR2(KTR_LOCK, "mtx_init 0x%p (%s)", m, t);
#ifdef MUTEX_DEBUG
if (mtx_validate(m, MV_INIT)) /* diagnostic and error correction */
return;
if (flag & MTX_COLD)
debug = m->mtx_debug;
else
debug = NULL;
if (debug == NULL) {
#ifdef DIAGNOSTIC
if(cold && bootverbose)
printf("malloc'ing mtx_debug while cold for %s\n", t);
#endif
/* XXX - should not use DEVBUF */
debug = malloc(sizeof(struct mtx_debug), M_DEVBUF, M_NOWAIT);
MPASS(debug != NULL);
bzero(debug, sizeof(struct mtx_debug));
}
#endif
bzero((void *)m, sizeof *m);
TAILQ_INIT(&m->mtx_blocked);
#ifdef MUTEX_DEBUG
m->mtx_debug = debug;
#endif
m->mtx_description = t;
m->mtx_lock = MTX_UNOWNED;
/* Put on all mutex queue */
mtx_enter(&all_mtx, MTX_DEF);
m->mtx_next = &all_mtx;
m->mtx_prev = all_mtx.mtx_prev;
m->mtx_prev->mtx_next = m;
all_mtx.mtx_prev = m;
if (++mtx_cur_cnt > mtx_max_cnt)
mtx_max_cnt = mtx_cur_cnt;
mtx_exit(&all_mtx, MTX_DEF);
witness_init(m, flag);
}
void
mtx_destroy(struct mtx *m)
{
CTR2(KTR_LOCK, "mtx_destroy 0x%p (%s)", m, m->mtx_description);
#ifdef MUTEX_DEBUG
if (m->mtx_next == NULL)
panic("mtx_destroy: %p (%s) already destroyed",
m, m->mtx_description);
if (!mtx_owned(m)) {
MPASS(m->mtx_lock == MTX_UNOWNED);
} else {
MPASS((m->mtx_lock & (MTX_RECURSE|MTX_CONTESTED)) == 0);
}
mtx_validate(m, MV_DESTROY); /* diagnostic */
#endif
#ifdef WITNESS
if (m->mtx_witness)
witness_destroy(m);
#endif /* WITNESS */
/* Remove from the all mutex queue */
mtx_enter(&all_mtx, MTX_DEF);
m->mtx_next->mtx_prev = m->mtx_prev;
m->mtx_prev->mtx_next = m->mtx_next;
#ifdef MUTEX_DEBUG
m->mtx_next = m->mtx_prev = NULL;
free(m->mtx_debug, M_DEVBUF);
m->mtx_debug = NULL;
#endif
mtx_cur_cnt--;
mtx_exit(&all_mtx, MTX_DEF);
}
/*
* The non-inlined versions of the mtx_*() functions are always built (above),
* but the witness code depends on the MUTEX_DEBUG and WITNESS kernel options
* being specified.
*/
#if (defined(MUTEX_DEBUG) && defined(WITNESS))
#define WITNESS_COUNT 200
#define WITNESS_NCHILDREN 2
int witness_watch = 1;
struct witness {
struct witness *w_next;
const char *w_description;
const char *w_file;
int w_line;
struct witness *w_morechildren;
u_char w_childcnt;
u_char w_Giant_squawked:1;
u_char w_other_squawked:1;
u_char w_same_squawked:1;
u_char w_sleep:1;
u_char w_spin:1; /* this is a spin mutex */
u_int w_level;
struct witness *w_children[WITNESS_NCHILDREN];
};
struct witness_blessed {
char *b_lock1;
char *b_lock2;
};
#ifdef DDB
/*
* When DDB is enabled and witness_ddb is set to 1, it will cause the system to
* drop into kdebug() when:
* - a lock heirarchy violation occurs
* - locks are held when going to sleep.
*/
#ifdef WITNESS_DDB
int witness_ddb = 1;
#else
int witness_ddb = 0;
#endif
SYSCTL_INT(_debug, OID_AUTO, witness_ddb, CTLFLAG_RW, &witness_ddb, 0, "");
#endif /* DDB */
#ifdef WITNESS_SKIPSPIN
int witness_skipspin = 1;
#else
int witness_skipspin = 0;
#endif
SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0,
"");
MUTEX_DECLARE(static,w_mtx);
static struct witness *w_free;
static struct witness *w_all;
static int w_inited;
static int witness_dead; /* fatal error, probably no memory */
static struct witness w_data[WITNESS_COUNT];
static struct witness *enroll __P((const char *description, int flag));
static int itismychild __P((struct witness *parent, struct witness *child));
static void removechild __P((struct witness *parent, struct witness *child));
static int isitmychild __P((struct witness *parent, struct witness *child));
static int isitmydescendant __P((struct witness *parent, struct witness *child));
static int dup_ok __P((struct witness *));
static int blessed __P((struct witness *, struct witness *));
static void witness_displaydescendants
__P((void(*)(const char *fmt, ...), struct witness *));
static void witness_leveldescendents __P((struct witness *parent, int level));
static void witness_levelall __P((void));
static struct witness * witness_get __P((void));
static void witness_free __P((struct witness *m));
static char *ignore_list[] = {
"witness lock",
NULL
};
static char *spin_order_list[] = {
"sio",
"sched lock",
#ifdef __i386__
"clk",
#endif
"callout",
/*
* leaf locks
*/
NULL
};
static char *order_list[] = {
"uidinfo hash", "uidinfo struct", NULL,
NULL
};
static char *dup_list[] = {
NULL
};
static char *sleep_list[] = {
"Giant",
NULL
};
/*
* Pairs of locks which have been blessed
* Don't complain about order problems with blessed locks
*/
static struct witness_blessed blessed_list[] = {
};
static int blessed_count = sizeof(blessed_list) / sizeof(struct witness_blessed);
void
witness_init(struct mtx *m, int flag)
{
m->mtx_witness = enroll(m->mtx_description, flag);
}
void
witness_destroy(struct mtx *m)
{
struct mtx *m1;
struct proc *p;
p = CURPROC;
for ((m1 = LIST_FIRST(&p->p_heldmtx)); m1 != NULL;
m1 = LIST_NEXT(m1, mtx_held)) {
if (m1 == m) {
LIST_REMOVE(m, mtx_held);
break;
}
}
return;
}
void
witness_enter(struct mtx *m, int flags, const char *file, int line)
{
struct witness *w, *w1;
struct mtx *m1;
struct proc *p;
int i;
#ifdef DDB
int go_into_ddb = 0;
#endif /* DDB */
w = m->mtx_witness;
p = CURPROC;
if (flags & MTX_SPIN) {
if (!w->w_spin)
panic("mutex_enter: MTX_SPIN on MTX_DEF mutex %s @"
" %s:%d", m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
mtx_enter(&w_mtx, MTX_SPIN);
i = witness_spin_check;
if (i != 0 && w->w_level < i) {
mtx_exit(&w_mtx, MTX_SPIN);
panic("mutex_enter(%s:%x, MTX_SPIN) out of order @"
" %s:%d already holding %s:%x",
m->mtx_description, w->w_level, file, line,
spin_order_list[ffs(i)-1], i);
}
PCPU_SET(witness_spin_check, i | w->w_level);
mtx_exit(&w_mtx, MTX_SPIN);
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
return;
}
if (w->w_spin)
panic("mutex_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
if (witness_dead)
goto out;
if (cold || panicstr)
goto out;
if (!mtx_legal2block())
panic("blockable mtx_enter() of %s when not legal @ %s:%d",
m->mtx_description, file, line);
/*
* Is this the first mutex acquired
*/
if ((m1 = LIST_FIRST(&p->p_heldmtx)) == NULL)
goto out;
if ((w1 = m1->mtx_witness) == w) {
if (w->w_same_squawked || dup_ok(w))
goto out;
w->w_same_squawked = 1;
printf("acquring duplicate lock of same type: \"%s\"\n",
m->mtx_description);
printf(" 1st @ %s:%d\n", w->w_file, w->w_line);
printf(" 2nd @ %s:%d\n", file, line);
#ifdef DDB
go_into_ddb = 1;
#endif /* DDB */
goto out;
}
MPASS(!mtx_owned(&w_mtx));
mtx_enter(&w_mtx, MTX_SPIN);
/*
* If we have a known higher number just say ok
*/
if (witness_watch > 1 && w->w_level > w1->w_level) {
mtx_exit(&w_mtx, MTX_SPIN);
goto out;
}
if (isitmydescendant(m1->mtx_witness, w)) {
mtx_exit(&w_mtx, MTX_SPIN);
goto out;
}
for (i = 0; m1 != NULL; m1 = LIST_NEXT(m1, mtx_held), i++) {
MPASS(i < 200);
w1 = m1->mtx_witness;
if (isitmydescendant(w, w1)) {
mtx_exit(&w_mtx, MTX_SPIN);
if (blessed(w, w1))
goto out;
if (m1 == &Giant) {
if (w1->w_Giant_squawked)
goto out;
else
w1->w_Giant_squawked = 1;
} else {
if (w1->w_other_squawked)
goto out;
else
w1->w_other_squawked = 1;
}
printf("lock order reversal\n");
printf(" 1st %s last acquired @ %s:%d\n",
w->w_description, w->w_file, w->w_line);
printf(" 2nd %p %s @ %s:%d\n",
m1, w1->w_description, w1->w_file, w1->w_line);
printf(" 3rd %p %s @ %s:%d\n",
m, w->w_description, file, line);
#ifdef DDB
go_into_ddb = 1;
#endif /* DDB */
goto out;
}
}
m1 = LIST_FIRST(&p->p_heldmtx);
if (!itismychild(m1->mtx_witness, w))
mtx_exit(&w_mtx, MTX_SPIN);
out:
#ifdef DDB
if (witness_ddb && go_into_ddb)
Debugger("witness_enter");
#endif /* DDB */
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
/*
* If this pays off it likely means that a mutex being witnessed
* is acquired in hardclock. Put it in the ignore list. It is
* likely not the mutex this assert fails on.
*/
MPASS(m->mtx_held.le_prev == NULL);
LIST_INSERT_HEAD(&p->p_heldmtx, (struct mtx*)m, mtx_held);
}
void
witness_exit(struct mtx *m, int flags, const char *file, int line)
{
struct witness *w;
w = m->mtx_witness;
if (flags & MTX_SPIN) {
if (!w->w_spin)
panic("mutex_exit: MTX_SPIN on MTX_DEF mutex %s @"
" %s:%d", m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
mtx_enter(&w_mtx, MTX_SPIN);
PCPU_SET(witness_spin_check, witness_spin_check & ~w->w_level);
mtx_exit(&w_mtx, MTX_SPIN);
return;
}
if (w->w_spin)
panic("mutex_exit: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
if ((flags & MTX_NOSWITCH) == 0 && !mtx_legal2block() && !cold)
panic("switchable mtx_exit() of %s when not legal @ %s:%d",
m->mtx_description, file, line);
LIST_REMOVE(m, mtx_held);
m->mtx_held.le_prev = NULL;
}
void
witness_try_enter(struct mtx *m, int flags, const char *file, int line)
{
struct proc *p;
struct witness *w = m->mtx_witness;
if (flags & MTX_SPIN) {
if (!w->w_spin)
panic("mutex_try_enter: "
"MTX_SPIN on MTX_DEF mutex %s @ %s:%d",
m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
mtx_enter(&w_mtx, MTX_SPIN);
PCPU_SET(witness_spin_check, witness_spin_check | w->w_level);
mtx_exit(&w_mtx, MTX_SPIN);
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
return;
}
if (w->w_spin)
panic("mutex_try_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (m->mtx_recurse != 0)
return;
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
p = CURPROC;
MPASS(m->mtx_held.le_prev == NULL);
LIST_INSERT_HEAD(&p->p_heldmtx, (struct mtx*)m, mtx_held);
}
void
witness_display(void(*prnt)(const char *fmt, ...))
{
struct witness *w, *w1;
witness_levelall();
for (w = w_all; w; w = w->w_next) {
if (w->w_file == NULL)
continue;
for (w1 = w_all; w1; w1 = w1->w_next) {
if (isitmychild(w1, w))
break;
}
if (w1 != NULL)
continue;
/*
* This lock has no anscestors, display its descendants.
*/
witness_displaydescendants(prnt, w);
}
prnt("\nMutex which were never acquired\n");
for (w = w_all; w; w = w->w_next) {
if (w->w_file != NULL)
continue;
prnt("%s\n", w->w_description);
}
}
int
witness_sleep(int check_only, struct mtx *mtx, const char *file, int line)
{
struct mtx *m;
struct proc *p;
char **sleep;
int n = 0;
p = CURPROC;
for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
m = LIST_NEXT(m, mtx_held)) {
if (m == mtx)
continue;
for (sleep = sleep_list; *sleep!= NULL; sleep++)
if (strcmp(m->mtx_description, *sleep) == 0)
goto next;
printf("%s:%d: %s with \"%s\" locked from %s:%d\n",
file, line, check_only ? "could sleep" : "sleeping",
m->mtx_description,
m->mtx_witness->w_file, m->mtx_witness->w_line);
n++;
next:
}
#ifdef DDB
if (witness_ddb && n)
Debugger("witness_sleep");
#endif /* DDB */
return (n);
}
static struct witness *
enroll(const char *description, int flag)
{
int i;
struct witness *w, *w1;
char **ignore;
char **order;
if (!witness_watch)
return (NULL);
for (ignore = ignore_list; *ignore != NULL; ignore++)
if (strcmp(description, *ignore) == 0)
return (NULL);
if (w_inited == 0) {
mtx_init(&w_mtx, "witness lock", MTX_COLD | MTX_DEF);
for (i = 0; i < WITNESS_COUNT; i++) {
w = &w_data[i];
witness_free(w);
}
w_inited = 1;
for (order = order_list; *order != NULL; order++) {
w = enroll(*order, MTX_DEF);
w->w_file = "order list";
for (order++; *order != NULL; order++) {
w1 = enroll(*order, MTX_DEF);
w1->w_file = "order list";
itismychild(w, w1);
w = w1;
}
}
}
if ((flag & MTX_SPIN) && witness_skipspin)
return (NULL);
mtx_enter(&w_mtx, MTX_SPIN);
for (w = w_all; w; w = w->w_next) {
if (strcmp(description, w->w_description) == 0) {
mtx_exit(&w_mtx, MTX_SPIN);
return (w);
}
}
if ((w = witness_get()) == NULL)
return (NULL);
w->w_next = w_all;
w_all = w;
w->w_description = description;
mtx_exit(&w_mtx, MTX_SPIN);
if (flag & MTX_SPIN) {
w->w_spin = 1;
i = 1;
for (order = spin_order_list; *order != NULL; order++) {
if (strcmp(description, *order) == 0)
break;
i <<= 1;
}
if (*order == NULL)
panic("spin lock %s not in order list", description);
w->w_level = i;
}
return (w);
}
static int
itismychild(struct witness *parent, struct witness *child)
{
static int recursed;
/*
* Insert "child" after "parent"
*/
while (parent->w_morechildren)
parent = parent->w_morechildren;
if (parent->w_childcnt == WITNESS_NCHILDREN) {
if ((parent->w_morechildren = witness_get()) == NULL)
return (1);
parent = parent->w_morechildren;
}
MPASS(child != NULL);
parent->w_children[parent->w_childcnt++] = child;
/*
* now prune whole tree
*/
if (recursed)
return (0);
recursed = 1;
for (child = w_all; child != NULL; child = child->w_next) {
for (parent = w_all; parent != NULL;
parent = parent->w_next) {
if (!isitmychild(parent, child))
continue;
removechild(parent, child);
if (isitmydescendant(parent, child))
continue;
itismychild(parent, child);
}
}
recursed = 0;
witness_levelall();
return (0);
}
static void
removechild(struct witness *parent, struct witness *child)
{
struct witness *w, *w1;
int i;
for (w = parent; w != NULL; w = w->w_morechildren)
for (i = 0; i < w->w_childcnt; i++)
if (w->w_children[i] == child)
goto found;
return;
found:
for (w1 = w; w1->w_morechildren != NULL; w1 = w1->w_morechildren)
continue;
w->w_children[i] = w1->w_children[--w1->w_childcnt];
MPASS(w->w_children[i] != NULL);
if (w1->w_childcnt != 0)
return;
if (w1 == parent)
return;
for (w = parent; w->w_morechildren != w1; w = w->w_morechildren)
continue;
w->w_morechildren = 0;
witness_free(w1);
}
static int
isitmychild(struct witness *parent, struct witness *child)
{
struct witness *w;
int i;
for (w = parent; w != NULL; w = w->w_morechildren) {
for (i = 0; i < w->w_childcnt; i++) {
if (w->w_children[i] == child)
return (1);
}
}
return (0);
}
static int
isitmydescendant(struct witness *parent, struct witness *child)
{
struct witness *w;
int i;
int j;
for (j = 0, w = parent; w != NULL; w = w->w_morechildren, j++) {
MPASS(j < 1000);
for (i = 0; i < w->w_childcnt; i++) {
if (w->w_children[i] == child)
return (1);
}
for (i = 0; i < w->w_childcnt; i++) {
if (isitmydescendant(w->w_children[i], child))
return (1);
}
}
return (0);
}
void
witness_levelall (void)
{
struct witness *w, *w1;
for (w = w_all; w; w = w->w_next)
if (!w->w_spin)
w->w_level = 0;
for (w = w_all; w; w = w->w_next) {
if (w->w_spin)
continue;
for (w1 = w_all; w1; w1 = w1->w_next) {
if (isitmychild(w1, w))
break;
}
if (w1 != NULL)
continue;
witness_leveldescendents(w, 0);
}
}
static void
witness_leveldescendents(struct witness *parent, int level)
{
int i;
struct witness *w;
if (parent->w_level < level)
parent->w_level = level;
level++;
for (w = parent; w != NULL; w = w->w_morechildren)
for (i = 0; i < w->w_childcnt; i++)
witness_leveldescendents(w->w_children[i], level);
}
static void
witness_displaydescendants(void(*prnt)(const char *fmt, ...),
struct witness *parent)
{
struct witness *w;
int i;
int level = parent->w_level;
prnt("%d", level);
if (level < 10)
prnt(" ");
for (i = 0; i < level; i++)
prnt(" ");
prnt("%s", parent->w_description);
if (parent->w_file != NULL) {
prnt(" -- last acquired @ %s", parent->w_file);
#ifndef W_USE_WHERE
prnt(":%d", parent->w_line);
#endif
prnt("\n");
}
for (w = parent; w != NULL; w = w->w_morechildren)
for (i = 0; i < w->w_childcnt; i++)
witness_displaydescendants(prnt, w->w_children[i]);
}
static int
dup_ok(struct witness *w)
{
char **dup;
for (dup = dup_list; *dup!= NULL; dup++)
if (strcmp(w->w_description, *dup) == 0)
return (1);
return (0);
}
static int
blessed(struct witness *w1, struct witness *w2)
{
int i;
struct witness_blessed *b;
for (i = 0; i < blessed_count; i++) {
b = &blessed_list[i];
if (strcmp(w1->w_description, b->b_lock1) == 0) {
if (strcmp(w2->w_description, b->b_lock2) == 0)
return (1);
continue;
}
if (strcmp(w1->w_description, b->b_lock2) == 0)
if (strcmp(w2->w_description, b->b_lock1) == 0)
return (1);
}
return (0);
}
static struct witness *
witness_get()
{
struct witness *w;
if ((w = w_free) == NULL) {
witness_dead = 1;
mtx_exit(&w_mtx, MTX_SPIN);
printf("witness exhausted\n");
return (NULL);
}
w_free = w->w_next;
bzero(w, sizeof(*w));
return (w);
}
static void
witness_free(struct witness *w)
{
w->w_next = w_free;
w_free = w;
}
void
witness_list(struct proc *p)
{
struct mtx *m;
for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
m = LIST_NEXT(m, mtx_held)) {
printf("\t\"%s\" (%p) locked at %s:%d\n",
m->mtx_description, m,
m->mtx_witness->w_file, m->mtx_witness->w_line);
}
}
void
witness_save(struct mtx *m, const char **filep, int *linep)
{
*filep = m->mtx_witness->w_file;
*linep = m->mtx_witness->w_line;
}
void
witness_restore(struct mtx *m, const char *file, int line)
{
m->mtx_witness->w_file = file;
m->mtx_witness->w_line = line;
}
#endif /* (defined(MUTEX_DEBUG) && defined(WITNESS)) */
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