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freebsd-dev/sys/kern/kern_mutex.c
John Baldwin 6936206ebd Split the WITNESS and MUTEX_DEBUG options apart so that WITNESS does not 
depend on MUTEX_DEBUG.  The MUTEX_DEBUG option turns on extra assertions
and checks to verify that mutexes themselves are implemented properly.
The WITNESS option uses extra checks and diagnostics to verify that other
code is using mutexes properly.
2000-12-01 00:10:59 +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 WITNESS
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 /* WITNESS */
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 /* WITNESS */
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 *);
#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;
mtx_assert(&sched_lock, MA_OWNED);
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);
KASSERT(p->p_stat != SSLEEP, ("sleeping process owns a mutex"));
if (p->p_priority <= pri)
return;
/*
* Bump this process' priority.
*/
SET_PRIO(p, pri);
/*
* If lock holder is actually running, just bump priority.
*/
#ifdef SMP
/*
* For SMP, we can check the p_oncpu field to see if we are
* running.
*/
if (p->p_oncpu != 0xff) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
return;
}
#else
/*
* For UP, we check to see if p is curproc (this shouldn't
* ever happen however as it would mean we are in a deadlock.)
*/
if (p == curproc) {
panic("Deadlock detected");
return;
}
#endif
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
printf("XXX: moving process %d(%s) to a new run queue\n",
p->p_pid, p->p_comm);
MPASS(p->p_blocked == NULL);
remrunqueue(p);
setrunqueue(p);
return;
}
/*
* If we aren't blocked on a mutex, we should be.
*/
KASSERT(p->p_stat == SMTX, (
"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));
/*
* 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 (p == TAILQ_FIRST(&m->mtx_blocked)) {
printf("XXX: process at head of run queue\n");
continue;
}
p1 = TAILQ_PREV(p, rq, p_procq);
if (p1->p_priority <= pri) {
printf(
"XXX: previous process %d(%s) has higher priority\n",
p->p_pid, p->p_comm);
continue;
}
/*
* Remove proc from blocked chain and determine where
* it should be moved up to. Since we know that p1 has
* a lower priority than p, we know that at least one
* process in the chain has a lower priority and that
* p1 will thus not be NULL after the loop.
*/
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;
}
MPASS(p1 != NULL);
TAILQ_INSERT_BEFORE(p1, 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));
/*
* Save our priority. Even though p_nativepri is protected
* by sched_lock, we don't obtain it here as it can be
* expensive. Since this is the only place p_nativepri is
* set, and since two CPUs will not be executing the same
* process concurrently, we know that no other CPU is going
* to be messing with this. Also, p_nativepri is only read
* when we are blocked on a mutex, so that can't be happening
* right now either.
*/
p->p_nativepri = p->p_priority;
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_mtxname = m->mtx_description;
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_mtxname = 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 WITNESS
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;
#endif
#ifdef WITNESS
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 WITNESS
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;
#endif
#ifdef WITNESS
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 WITNESS kernel option being specified.
*/
#ifdef 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 /* WITNESS */
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