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freebsd-dev/sys/kern/kern_mutex.c
jhb 5c1fadddce Fix mtx_legal2block. The only time that it is bad to block on a mutex is 
if we hold a spin mutex, since we can trivially get into deadlocks if we
start switching out of processes that hold spinlocks.  Checking to see if
interrupts were disabled was a sort of cheap way of doing this since most
of the time interrupts were only disabled when holding a spin lock.  At
least on the i386.  To fix this properly, use a per-process counter
p_spinlocks that counts the number of spin locks currently held, and
instead of checking to see if interrupts are disabled in the witness code,
check to see if we hold any spin locks.  Since child processes always
start up with the sched lock magically held in fork_exit(), we initialize
p_spinlocks to 1 for child processes.  Note that proc0 doesn't go through
fork_exit(), so it starts with no spin locks held.

Consulting from:	cp
2001-03-09 07:24:17 +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 $
* $FreeBSD$
*/
/*
* Machine independent bits of mutex implementation and implementation of
* `witness' structure & related debugging routines.
*/
/*
* 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"
#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>
/*
* The WITNESS-enabled mutex debug structure.
*/
#ifdef WITNESS
struct mtx_debug {
struct witness *mtxd_witness;
LIST_ENTRY(mtx) mtxd_held;
const char *mtxd_file;
int mtxd_line;
};
#define mtx_held mtx_debug->mtxd_held
#define mtx_file mtx_debug->mtxd_file
#define mtx_line mtx_debug->mtxd_line
#define mtx_witness mtx_debug->mtxd_witness
#endif /* WITNESS */
/*
* Internal utility macros.
*/
#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 SET_PRIO(p, pri) (p)->p_pri.pri_level = (pri)
/*
* Early WITNESS-enabled declarations.
*/
#ifdef WITNESS
/*
* Internal WITNESS routines which must be prototyped early.
*
* XXX: When/if witness code is cleaned up, it would be wise to place all
* witness prototyping early in this file.
*/
static void witness_init(struct mtx *, int flag);
static void witness_destroy(struct mtx *);
static void witness_display(void(*)(const char *fmt, ...));
MALLOC_DEFINE(M_WITNESS, "witness", "witness mtx_debug structure");
/* All mutexes in system (used for debug/panic) */
static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0 };
/*
* This global is set to 0 once it becomes safe to use the witness code.
*/
static int witness_cold = 1;
#else /* WITNESS */
/* XXX XXX XXX
* flag++ is sleazoid way of shuting up warning
*/
#define witness_init(m, flag) flag++
#define witness_destroy(m)
#define witness_try_enter(m, t, f, l)
#endif /* WITNESS */
/*
* All mutex locks in system are kept on the all_mtx list.
*/
static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, 0, "All mutexes queue head",
TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
{ NULL, NULL }, &all_mtx, &all_mtx,
#ifdef WITNESS
&all_mtx_debug
#else
NULL
#endif
};
/*
* Global variables for book keeping.
*/
static int mtx_cur_cnt;
static int mtx_max_cnt;
/*
* Couple of strings for KTR_LOCK tracing in order to avoid duplicates.
*/
char STR_mtx_lock_slp[] = "GOT (sleep) %s [%p] r=%d at %s:%d";
char STR_mtx_unlock_slp[] = "REL (sleep) %s [%p] r=%d at %s:%d";
char STR_mtx_lock_spn[] = "GOT (spin) %s [%p] r=%d at %s:%d";
char STR_mtx_unlock_spn[] = "REL (spin) %s [%p] r=%d at %s:%d";
/*
* Prototypes for non-exported routines.
*
* NOTE: Prototypes for witness routines are placed at the bottom of the file.
*/
static void propagate_priority(struct proc *);
static void
propagate_priority(struct proc *p)
{
int pri = p->p_pri.pri_level;
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_pri.pri_level <= pri)
return;
/*
* Bump this process' priority.
*/
SET_PRIO(p, pri);
/*
* If lock holder is actually running, just bump priority.
*/
if (p->p_oncpu != NOCPU) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
return;
}
#ifndef SMP
/*
* 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.)
*/
KASSERT(p != curproc, ("Deadlock detected"));
#endif
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
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);
/*
* Check if the proc needs to be moved up on
* the blocked chain
*/
if (p == TAILQ_FIRST(&m->mtx_blocked)) {
continue;
}
p1 = TAILQ_PREV(p, procqueue, p_procq);
if (p1->p_pri.pri_level <= pri) {
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_pri.pri_level > pri)
break;
}
MPASS(p1 != NULL);
TAILQ_INSERT_BEFORE(p1, p, p_procq);
CTR4(KTR_LOCK,
"propagate_priority: p %p moved before %p on [%p] %s",
p, p1, m, m->mtx_description);
}
}
/*
* The important part of mtx_trylock{,_flags}()
* Tries to acquire lock `m.' We do NOT handle recursion here; we assume that
* if we're called, it's because we know we don't already own this lock.
*/
int
_mtx_trylock(struct mtx *m, int opts, const char *file, int line)
{
int rval;
MPASS(curproc != NULL);
/*
* _mtx_trylock does not accept MTX_NOSWITCH option.
*/
KASSERT((opts & MTX_NOSWITCH) == 0,
("mtx_trylock() called with invalid option flag(s) %d", opts));
rval = _obtain_lock(m, curproc);
#ifdef WITNESS
if (rval && m->mtx_witness != NULL) {
/*
* We do not handle recursion in _mtx_trylock; see the
* note at the top of the routine.
*/
KASSERT(!mtx_recursed(m),
("mtx_trylock() called on a recursed mutex"));
witness_try_enter(m, (opts | m->mtx_flags), file, line);
}
#endif /* WITNESS */
if ((opts & MTX_QUIET) == 0)
CTR5(KTR_LOCK, "TRY_LOCK %s [%p] result=%d at %s:%d",
m->mtx_description, m, rval, file, line);
return rval;
}
/*
* _mtx_lock_sleep: the tougher part of acquiring an MTX_DEF lock.
*
* We call this if the lock is either contested (i.e. we need to go to
* sleep waiting for it), or if we need to recurse on it.
*/
void
_mtx_lock_sleep(struct mtx *m, int opts, const char *file, int line)
{
struct proc *p = curproc;
if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)p) {
m->mtx_recurse++;
atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
if ((opts & MTX_QUIET) == 0)
CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
return;
}
if ((opts & MTX_QUIET) == 0)
CTR4(KTR_LOCK,
"_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
m->mtx_description, (void *)m->mtx_lock, file, line);
while (!_obtain_lock(m, p)) {
uintptr_t v;
struct proc *p1;
mtx_lock_spin(&sched_lock);
/*
* Check if the lock has been released while spinning for
* the sched_lock.
*/
if ((v = m->mtx_lock) == MTX_UNOWNED) {
mtx_unlock_spin(&sched_lock);
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);
MPASS(p1 != NULL);
m->mtx_lock = (uintptr_t)p | MTX_CONTESTED;
if (p1->p_pri.pri_level < p->p_pri.pri_level)
SET_PRIO(p, p1->p_pri.pri_level);
mtx_unlock_spin(&sched_lock);
return;
}
/*
* If the mutex isn't already contested and a failure occurs
* setting the contested bit, the mutex was either released
* or the state of the MTX_RECURSED bit changed.
*/
if ((v & MTX_CONTESTED) == 0 &&
!atomic_cmpset_ptr(&m->mtx_lock, (void *)v,
(void *)(v | MTX_CONTESTED))) {
mtx_unlock_spin(&sched_lock);
continue;
}
/*
* We deffinately must sleep for this lock.
*/
mtx_assert(m, MA_NOTOWNED);
#ifdef notyet
/*
* If we're borrowing an interrupted thread's VM context, we
* must clean up before going to sleep.
*/
if (p->p_ithd != NULL) {
struct ithd *it = p->p_ithd;
if (it->it_interrupted) {
if ((opts & MTX_QUIET) == 0)
CTR2(KTR_LOCK,
"_mtx_lock_sleep: %p interrupted %p",
it, it->it_interrupted);
intr_thd_fixup(it);
}
}
#endif
/*
* Put us on the list of threads 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_pri.pri_level > p->p_pri.pri_level)
break;
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
}
/*
* Save who we're blocked on.
*/
p->p_blocked = m;
p->p_mtxname = m->mtx_description;
p->p_stat = SMTX;
propagate_priority(p);
if ((opts & MTX_QUIET) == 0)
CTR3(KTR_LOCK,
"_mtx_lock_sleep: p %p blocked on [%p] %s", p, m,
m->mtx_description);
mi_switch();
if ((opts & MTX_QUIET) == 0)
CTR3(KTR_LOCK,
"_mtx_lock_sleep: p %p free from blocked on [%p] %s",
p, m, m->mtx_description);
mtx_unlock_spin(&sched_lock);
}
return;
}
/*
* _mtx_lock_spin: the tougher part of acquiring an MTX_SPIN lock.
*
* This is only called if we need to actually spin for the lock. Recursion
* is handled inline.
*/
void
_mtx_lock_spin(struct mtx *m, int opts, u_int mtx_intr, const char *file,
int line)
{
int i = 0;
if ((opts & MTX_QUIET) == 0)
CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
for (;;) {
if (_obtain_lock(m, curproc))
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 %p for > 5 seconds",
m->mtx_description, (void *)m->mtx_lock);
}
}
m->mtx_saveintr = mtx_intr;
if ((opts & MTX_QUIET) == 0)
CTR1(KTR_LOCK, "_mtx_lock_spin: %p spin done", m);
return;
}
/*
* _mtx_unlock_sleep: the tougher part of releasing an MTX_DEF lock.
*
* We are only called here if the lock is recursed or contested (i.e. we
* need to wake up a blocked thread).
*/
void
_mtx_unlock_sleep(struct mtx *m, int opts, const char *file, int line)
{
struct proc *p, *p1;
struct mtx *m1;
int pri;
p = curproc;
if (mtx_recursed(m)) {
if (--(m->mtx_recurse) == 0)
atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
if ((opts & MTX_QUIET) == 0)
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
return;
}
mtx_lock_spin(&sched_lock);
if ((opts & MTX_QUIET) == 0)
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %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);
if ((opts & MTX_QUIET) == 0)
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, &p->p_contested, mtx_contested) {
int cp = TAILQ_FIRST(&m1->mtx_blocked)->p_pri.pri_level;
if (cp < pri)
pri = cp;
}
if (pri > p->p_pri.pri_native)
pri = p->p_pri.pri_native;
SET_PRIO(p, pri);
if ((opts & MTX_QUIET) == 0)
CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p",
m, p1);
p1->p_blocked = NULL;
p1->p_stat = SRUN;
setrunqueue(p1);
if ((opts & MTX_NOSWITCH) == 0 && p1->p_pri.pri_level < pri) {
#ifdef notyet
if (p->p_ithd != NULL) {
struct ithd *it = p->p_ithd;
if (it->it_interrupted) {
if ((opts & MTX_QUIET) == 0)
CTR2(KTR_LOCK,
"_mtx_unlock_sleep: %p interrupted %p",
it, it->it_interrupted);
intr_thd_fixup(it);
}
}
#endif
setrunqueue(p);
if ((opts & MTX_QUIET) == 0)
CTR2(KTR_LOCK,
"_mtx_unlock_sleep: %p switching out lock=%p", m,
(void *)m->mtx_lock);
mi_switch();
if ((opts & MTX_QUIET) == 0)
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)
{
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_description, file, line);
if (mtx_recursed(m)) {
if ((what & MA_NOTRECURSED) != 0)
panic("mutex %s recursed at %s:%d",
m->mtx_description, file, line);
} else if ((what & MA_RECURSED) != 0) {
panic("mutex %s unrecursed at %s:%d",
m->mtx_description, file, line);
}
break;
case MA_NOTOWNED:
if (mtx_owned(m))
panic("mutex %s owned at %s:%d",
m->mtx_description, file, line);
break;
default:
panic("unknown mtx_assert at %s:%d", file, line);
}
}
#endif
/*
* The MUTEX_DEBUG-enabled mtx_validate()
*/
#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;
#ifdef WITNESS
if (witness_cold)
return 0;
#endif
if (m == &all_mtx || cold)
return 0;
mtx_lock(&all_mtx);
/*
* 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_unlock(&all_mtx);
return (retval);
}
#endif
/*
* Mutex initialization routine; initialize lock `m' of type contained in
* `opts' with options contained in `opts' and description `description.'
* Place on "all_mtx" queue.
*/
void
mtx_init(struct mtx *m, const char *description, int opts)
{
if ((opts & MTX_QUIET) == 0)
CTR2(KTR_LOCK, "mtx_init %p (%s)", m, description);
#ifdef MUTEX_DEBUG
/* Diagnostic and error correction */
if (mtx_validate(m, MV_INIT))
return;
#endif
bzero((void *)m, sizeof *m);
TAILQ_INIT(&m->mtx_blocked);
#ifdef WITNESS
if (!witness_cold) {
m->mtx_debug = malloc(sizeof(struct mtx_debug),
M_WITNESS, M_NOWAIT | M_ZERO);
MPASS(m->mtx_debug != NULL);
}
#endif
m->mtx_description = description;
m->mtx_flags = opts;
m->mtx_lock = MTX_UNOWNED;
/* Put on all mutex queue */
mtx_lock(&all_mtx);
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_unlock(&all_mtx);
#ifdef WITNESS
if (!witness_cold)
witness_init(m, opts);
#endif
}
/*
* Remove lock `m' from all_mtx queue.
*/
void
mtx_destroy(struct mtx *m)
{
#ifdef WITNESS
KASSERT(!witness_cold, ("%s: Cannot destroy while still cold\n",
__FUNCTION__));
#endif
CTR2(KTR_LOCK, "mtx_destroy %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_RECURSED|MTX_CONTESTED)) == 0);
}
/* diagnostic */
mtx_validate(m, MV_DESTROY);
#endif
#ifdef WITNESS
if (m->mtx_witness)
witness_destroy(m);
#endif /* WITNESS */
/* Remove from the all mutex queue */
mtx_lock(&all_mtx);
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_WITNESS);
m->mtx_debug = NULL;
#endif
mtx_cur_cnt--;
mtx_unlock(&all_mtx);
}
/*
* The WITNESS-enabled diagnostic code.
*/
#ifdef WITNESS
static void
witness_fixup(void *dummy __unused)
{
struct mtx *mp;
/*
* We have to release Giant before initializing its witness
* structure so that WITNESS doesn't get confused.
*/
mtx_unlock(&Giant);
mtx_assert(&Giant, MA_NOTOWNED);
mtx_lock(&all_mtx);
/* Iterate through all mutexes and finish up mutex initialization. */
for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) {
mp->mtx_debug = malloc(sizeof(struct mtx_debug),
M_WITNESS, M_NOWAIT | M_ZERO);
MPASS(mp->mtx_debug != NULL);
witness_init(mp, mp->mtx_flags);
}
mtx_unlock(&all_mtx);
/* Mark the witness code as being ready for use. */
atomic_store_rel_int(&witness_cold, 0);
mtx_lock(&Giant);
}
SYSINIT(wtnsfxup, SI_SUB_MUTEX, SI_ORDER_FIRST, witness_fixup, NULL)
#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_spin:1; /* MTX_SPIN type 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.
*/
int witness_ddb;
#ifdef WITNESS_DDB
TUNABLE_INT_DECL("debug.witness_ddb", 1, witness_ddb);
#else
TUNABLE_INT_DECL("debug.witness_ddb", 0, witness_ddb);
#endif
SYSCTL_INT(_debug, OID_AUTO, witness_ddb, CTLFLAG_RW, &witness_ddb, 0, "");
#endif /* DDB */
int witness_skipspin;
#ifdef WITNESS_SKIPSPIN
TUNABLE_INT_DECL("debug.witness_skipspin", 1, witness_skipspin);
#else
TUNABLE_INT_DECL("debug.witness_skipspin", 0, witness_skipspin);
#endif
SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0,
"");
/*
* Witness-enabled globals
*/
static struct mtx 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];
/*
* Internal witness routine prototypes
*/
static struct witness *enroll(const char *description, int flag);
static int itismychild(struct witness *parent, struct witness *child);
static void removechild(struct witness *parent, struct witness *child);
static int isitmychild(struct witness *parent, struct witness *child);
static int isitmydescendant(struct witness *parent, struct witness *child);
static int dup_ok(struct witness *);
static int blessed(struct witness *, struct witness *);
static void
witness_displaydescendants(void(*)(const char *fmt, ...), struct witness *);
static void witness_leveldescendents(struct witness *parent, int level);
static void witness_levelall(void);
static struct witness * witness_get(void);
static void witness_free(struct witness *m);
static char *ignore_list[] = {
"witness lock",
NULL
};
static char *spin_order_list[] = {
#if defined(__i386__) && defined (SMP)
"com",
#endif
"sio",
#ifdef __i386__
"cy",
#endif
"ng_node",
"ng_worklist",
"ithread table lock",
"ithread list lock",
"sched lock",
#ifdef __i386__
"clk",
#endif
"callout",
/*
* leaf locks
*/
#ifdef SMP
#ifdef __i386__
"ap boot",
"imen",
#endif
"smp rendezvous",
#endif
NULL
};
static char *order_list[] = {
"Giant", "proctree", "allproc", "process lock", "uidinfo hash",
"uidinfo struct", NULL,
NULL
};
static char *dup_list[] = {
"process lock",
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);
static void
witness_init(struct mtx *m, int flag)
{
m->mtx_witness = enroll(m->mtx_description, flag);
}
static void
witness_destroy(struct mtx *m)
{
struct mtx *m1;
struct proc *p;
p = curproc;
LIST_FOREACH(m1, &p->p_heldmtx, mtx_held) {
if (m1 == m) {
LIST_REMOVE(m, mtx_held);
break;
}
}
return;
}
static void
witness_display(void(*prnt)(const char *fmt, ...))
{
struct witness *w, *w1;
int level, found;
KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
witness_levelall();
/*
* First, handle sleep mutexes which have been acquired at least
* once.
*/
prnt("Sleep mutexes:\n");
for (w = w_all; w; w = w->w_next) {
if (w->w_file == NULL || w->w_spin)
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);
}
/*
* Now do spin mutexes which have been acquired at least once.
*/
prnt("\nSpin mutexes:\n");
level = 0;
while (level < sizeof(spin_order_list) / sizeof(char *)) {
found = 0;
for (w = w_all; w; w = w->w_next) {
if (w->w_file == NULL || !w->w_spin)
continue;
if (w->w_level == 1 << level) {
witness_displaydescendants(prnt, w);
level++;
found = 1;
}
}
if (found == 0)
level++;
}
/*
* Finally, any mutexes which have not been acquired yet.
*/
prnt("\nMutexes 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);
}
}
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 */
if (witness_cold || m->mtx_witness == NULL || panicstr)
return;
w = m->mtx_witness;
p = curproc;
if (flags & MTX_SPIN) {
if ((m->mtx_flags & MTX_SPIN) == 0)
panic("mutex_enter: MTX_SPIN on MTX_DEF mutex %s @"
" %s:%d", m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_enter: recursion on non-recursive"
" mutex %s @ %s:%d", m->mtx_description,
file, line);
return;
}
mtx_lock_spin_flags(&w_mtx, MTX_QUIET);
i = PCPU_GET(witness_spin_check);
if (i != 0 && w->w_level < i) {
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
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_unlock_spin_flags(&w_mtx, MTX_QUIET);
p->p_spinlocks++;
MPASS(p->p_spinlocks > 0);
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
return;
}
if ((m->mtx_flags & MTX_SPIN) != 0)
panic("mutex_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_enter: recursion on non-recursive"
" mutex %s @ %s:%d", m->mtx_description,
file, line);
return;
}
if (witness_dead)
goto out;
if (cold)
goto out;
if (p->p_spinlocks != 0)
panic("blockable mtx_lock() 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_lock_spin_flags(&w_mtx, MTX_QUIET);
/*
* If we have a known higher number just say ok
*/
if (witness_watch > 1 && w->w_level > w1->w_level) {
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
goto out;
}
if (isitmydescendant(m1->mtx_witness, w)) {
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
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_unlock_spin_flags(&w_mtx, MTX_QUIET);
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_unlock_spin_flags(&w_mtx, MTX_QUIET);
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_try_enter(struct mtx *m, int flags, const char *file, int line)
{
struct proc *p;
struct witness *w = m->mtx_witness;
if (witness_cold)
return;
if (panicstr)
return;
if (flags & MTX_SPIN) {
if ((m->mtx_flags & MTX_SPIN) == 0)
panic("mutex_try_enter: "
"MTX_SPIN on MTX_DEF mutex %s @ %s:%d",
m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_try_enter: recursion on"
" non-recursive mutex %s @ %s:%d",
m->mtx_description, file, line);
return;
}
mtx_lock_spin_flags(&w_mtx, MTX_QUIET);
PCPU_SET(witness_spin_check,
PCPU_GET(witness_spin_check) | w->w_level);
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
w->w_file = file;
w->w_line = line;
m->mtx_line = line;
m->mtx_file = file;
return;
}
if ((m->mtx_flags & MTX_SPIN) != 0)
panic("mutex_try_enter: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_try_enter: recursion on non-recursive"
" mutex %s @ %s:%d", m->mtx_description, file,
line);
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_exit(struct mtx *m, int flags, const char *file, int line)
{
struct witness *w;
struct proc *p;
if (witness_cold || m->mtx_witness == NULL || panicstr)
return;
w = m->mtx_witness;
p = curproc;
if (flags & MTX_SPIN) {
if ((m->mtx_flags & MTX_SPIN) == 0)
panic("mutex_exit: MTX_SPIN on MTX_DEF mutex %s @"
" %s:%d", m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_exit: recursion on non-recursive"
" mutex %s @ %s:%d", m->mtx_description,
file, line);
return;
}
mtx_lock_spin_flags(&w_mtx, MTX_QUIET);
PCPU_SET(witness_spin_check,
PCPU_GET(witness_spin_check) & ~w->w_level);
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
MPASS(p->p_spinlocks > 0);
p->p_spinlocks--;
return;
}
if ((m->mtx_flags & MTX_SPIN) != 0)
panic("mutex_exit: MTX_DEF on MTX_SPIN mutex %s @ %s:%d",
m->mtx_description, file, line);
if (mtx_recursed(m)) {
if ((m->mtx_flags & MTX_RECURSE) == 0)
panic("mutex_exit: recursion on non-recursive"
" mutex %s @ %s:%d", m->mtx_description,
file, line);
return;
}
if ((flags & MTX_NOSWITCH) == 0 && p->p_spinlocks != 0 && !cold)
panic("switchable mtx_unlock() of %s when not legal @ %s:%d",
m->mtx_description, file, line);
LIST_REMOVE(m, mtx_held);
m->mtx_held.le_prev = NULL;
}
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;
KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
p = curproc;
LIST_FOREACH(m, &p->p_heldmtx, mtx_held) {
if (m == mtx)
continue;
for (sleep = sleep_list; *sleep!= NULL; sleep++)
if (strcmp(m->mtx_description, *sleep) == 0)
goto next;
if (n == 0)
printf("Whee!\n");
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_SPIN);
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_lock_spin_flags(&w_mtx, MTX_QUIET);
for (w = w_all; w; w = w->w_next) {
if (strcmp(description, w->w_description) == 0) {
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
return (w);
}
}
if ((w = witness_get()) == NULL)
return (NULL);
w->w_next = w_all;
w_all = w;
w->w_description = description;
mtx_unlock_spin_flags(&w_mtx, MTX_QUIET);
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;
level = parent->w_spin ? ffs(parent->w_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:%d\n", parent->w_file,
parent->w_line);
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_unlock_spin_flags(&w_mtx, MTX_QUIET);
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;
}
int
witness_list(struct proc *p)
{
struct mtx *m;
int nheld;
KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
nheld = 0;
LIST_FOREACH(m, &p->p_heldmtx, 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);
nheld++;
}
return (nheld);
}
#ifdef DDB
DB_SHOW_COMMAND(mutexes, db_witness_list)
{
witness_list(curproc);
}
DB_SHOW_COMMAND(witness, db_witness_display)
{
witness_display(db_printf);
}
#endif
void
witness_save(struct mtx *m, const char **filep, int *linep)
{
KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
if (m->mtx_witness == NULL)
return;
*filep = m->mtx_witness->w_file;
*linep = m->mtx_witness->w_line;
}
void
witness_restore(struct mtx *m, const char *file, int line)
{
KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
if (m->mtx_witness == NULL)
return;
m->mtx_witness->w_file = file;
m->mtx_witness->w_line = line;
}
#endif /* WITNESS */
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