freebsd-dev/sys/kern/subr_turnstile.c
Matthew Dillon d23f5958bc Add mtx_lock_giant() and mtx_unlock_giant() wrappers for sysctl management
of Giant during the Giant unwinding phase, and start work on instrumenting
Giant for the file and proc mutexes.

These wrappers allow developers to turn on and off Giant around various
subsystems.  DEVELOPERS SHOULD NEVER TURN OFF GIANT AROUND A SUBSYSTEM JUST
BECAUSE THE SYSCTL EXISTS!  General developers should only considering
turning on Giant for a subsystem whos default is off (to help track down
bugs).  Only developers working on particular subsystems who know what
they are doing should consider turning off Giant.

These wrappers will greatly improve our ability to unwind Giant and test
the kernel on a (mostly) subsystem by subsystem basis.   They allow Giant
unwinding developers (GUDs) to emplace appropriate subsystem and structural
mutexes in the main tree and then request that the larger community test
the work by turning off Giant around the subsystem(s), without the larger
community having to mess around with patches.  These wrappers also allow
GUDs to boot into a (more likely to be) working system in the midst of
their unwinding work and to test that work under more controlled
circumstances.

There is a master sysctl, kern.giant.all, which defaults to 0 (off).  If
turned on it overrides *ALL* other kern.giant sysctls and forces Giant to
be turned on for all wrapped subsystems.  If turned off then Giant around
individual subsystems are controlled by various other kern.giant.XXX sysctls.

Code which overlaps multiple subsystems must have all related subsystem Giant
sysctls turned off in order to run without Giant.
2001-10-26 20:48:04 +00:00

765 lines
20 KiB
C

/*-
* 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 <sys/param.h>
#include <sys/bus.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/resourcevar.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>
/*
* Internal utility macros.
*/
#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
#define mtx_owner(m) (mtx_unowned((m)) ? NULL \
: (struct thread *)((m)->mtx_lock & MTX_FLAGMASK))
#define SET_PRIO(td, pri) (td)->td_ksegrp->kg_pri.pri_level = (pri)
/*
* Lock classes for sleep and spin mutexes.
*/
struct lock_class lock_class_mtx_sleep = {
"sleep mutex",
LC_SLEEPLOCK | LC_RECURSABLE
};
struct lock_class lock_class_mtx_spin = {
"spin mutex",
LC_SPINLOCK | LC_RECURSABLE
};
/*
* Prototypes for non-exported routines.
*/
static void propagate_priority(struct thread *);
static void
propagate_priority(struct thread *td)
{
struct ksegrp *kg = td->td_ksegrp;
int pri = kg->kg_pri.pri_level;
struct mtx *m = td->td_blocked;
mtx_assert(&sched_lock, MA_OWNED);
for (;;) {
struct thread *td1;
td = mtx_owner(m);
if (td == NULL) {
/*
* This really isn't quite right. Really
* ought to bump priority of thread that
* next acquires the mutex.
*/
MPASS(m->mtx_lock == MTX_CONTESTED);
return;
}
kg = td->td_ksegrp;
MPASS(td->td_proc->p_magic == P_MAGIC);
KASSERT(td->td_proc->p_stat != SSLEEP, ("sleeping thread owns a mutex"));
if (kg->kg_pri.pri_level <= pri) /* lower is higher priority */
return;
/*
* Bump this thread's priority.
*/
SET_PRIO(td, pri);
/*
* If lock holder is actually running, just bump priority.
*/
/* XXXKSE this test is not sufficient */
if (td->td_kse && (td->td_kse->ke_oncpu != NOCPU)) {
MPASS(td->td_proc->p_stat == SRUN
|| td->td_proc->p_stat == SZOMB
|| td->td_proc->p_stat == SSTOP);
return;
}
#ifndef SMP
/*
* For UP, we check to see if td is curthread (this shouldn't
* ever happen however as it would mean we are in a deadlock.)
*/
KASSERT(td != curthread, ("Deadlock detected"));
#endif
/*
* If on run queue move to new run queue, and quit.
* XXXKSE this gets a lot more complicated under threads
* but try anyhow.
*/
if (td->td_proc->p_stat == SRUN) {
MPASS(td->td_blocked == NULL);
remrunqueue(td);
setrunqueue(td);
return;
}
/*
* If we aren't blocked on a mutex, we should be.
*/
KASSERT(td->td_proc->p_stat == SMTX, (
"process %d(%s):%d holds %s but isn't blocked on a mutex\n",
td->td_proc->p_pid, td->td_proc->p_comm, td->td_proc->p_stat,
m->mtx_object.lo_name));
/*
* Pick up the mutex that td is blocked on.
*/
m = td->td_blocked;
MPASS(m != NULL);
/*
* Check if the thread needs to be moved up on
* the blocked chain
*/
if (td == TAILQ_FIRST(&m->mtx_blocked)) {
continue;
}
td1 = TAILQ_PREV(td, threadqueue, td_blkq);
if (td1->td_ksegrp->kg_pri.pri_level <= pri) {
continue;
}
/*
* Remove thread from blocked chain and determine where
* it should be moved up to. Since we know that td1 has
* a lower priority than td, we know that at least one
* thread in the chain has a lower priority and that
* td1 will thus not be NULL after the loop.
*/
TAILQ_REMOVE(&m->mtx_blocked, td, td_blkq);
TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq) {
MPASS(td1->td_proc->p_magic == P_MAGIC);
if (td1->td_ksegrp->kg_pri.pri_level > pri)
break;
}
MPASS(td1 != NULL);
TAILQ_INSERT_BEFORE(td1, td, td_blkq);
CTR4(KTR_LOCK,
"propagate_priority: p %p moved before %p on [%p] %s",
td, td1, m, m->mtx_object.lo_name);
}
}
/*
* Function versions of the inlined __mtx_* macros. These are used by
* modules and can also be called from assembly language if needed.
*/
void
_mtx_lock_flags(struct mtx *m, int opts, const char *file, int line)
{
MPASS(curthread != NULL);
KASSERT((opts & MTX_NOSWITCH) == 0,
("MTX_NOSWITCH used at %s:%d", file, line));
_get_sleep_lock(m, curthread, opts, file, line);
LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
line);
WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
}
void
_mtx_unlock_flags(struct mtx *m, int opts, const char *file, int line)
{
MPASS(curthread != NULL);
mtx_assert(m, MA_OWNED);
WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
line);
_rel_sleep_lock(m, curthread, opts, file, line);
}
void
_mtx_lock_spin_flags(struct mtx *m, int opts, const char *file, int line)
{
MPASS(curthread != NULL);
_get_spin_lock(m, curthread, opts, file, line);
LOCK_LOG_LOCK("LOCK", &m->mtx_object, opts, m->mtx_recurse, file,
line);
WITNESS_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
}
void
_mtx_unlock_spin_flags(struct mtx *m, int opts, const char *file, int line)
{
MPASS(curthread != NULL);
mtx_assert(m, MA_OWNED);
WITNESS_UNLOCK(&m->mtx_object, opts | LOP_EXCLUSIVE, file, line);
LOCK_LOG_LOCK("UNLOCK", &m->mtx_object, opts, m->mtx_recurse, file,
line);
_rel_spin_lock(m);
}
/*
* 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(curthread != 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, curthread);
LOCK_LOG_TRY("LOCK", &m->mtx_object, opts, rval, file, line);
if (rval) {
/*
* 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_LOCK(&m->mtx_object, opts | LOP_EXCLUSIVE | LOP_TRYLOCK,
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 thread *td = curthread;
struct ksegrp *kg = td->td_ksegrp;
if ((m->mtx_lock & MTX_FLAGMASK) == (uintptr_t)td) {
m->mtx_recurse++;
atomic_set_ptr(&m->mtx_lock, MTX_RECURSED);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR1(KTR_LOCK, "_mtx_lock_sleep: %p recursing", m);
return;
}
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR4(KTR_LOCK,
"_mtx_lock_sleep: %s contested (lock=%p) at %s:%d",
m->mtx_object.lo_name, (void *)m->mtx_lock, file, line);
while (!_obtain_lock(m, td)) {
uintptr_t v;
struct thread *td1;
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 threads blocked on it.
*/
if (v == MTX_CONTESTED) {
td1 = TAILQ_FIRST(&m->mtx_blocked);
MPASS(td1 != NULL);
m->mtx_lock = (uintptr_t)td | MTX_CONTESTED;
if (td1->td_ksegrp->kg_pri.pri_level < kg->kg_pri.pri_level)
SET_PRIO(td, td1->td_ksegrp->kg_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 (td->td_ithd != NULL) {
struct ithd *it = td->td_ithd;
if (it->it_interrupted) {
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR2(KTR_LOCK,
"_mtx_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)) {
td1 = (struct thread *)(m->mtx_lock & MTX_FLAGMASK);
LIST_INSERT_HEAD(&td1->td_contested, m, mtx_contested);
TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq);
} else {
TAILQ_FOREACH(td1, &m->mtx_blocked, td_blkq)
if (td1->td_ksegrp->kg_pri.pri_level > kg->kg_pri.pri_level)
break;
if (td1)
TAILQ_INSERT_BEFORE(td1, td, td_blkq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, td, td_blkq);
}
/*
* Save who we're blocked on.
*/
td->td_blocked = m;
td->td_mtxname = m->mtx_object.lo_name;
td->td_proc->p_stat = SMTX;
propagate_priority(td);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR3(KTR_LOCK,
"_mtx_lock_sleep: p %p blocked on [%p] %s", td, m,
m->mtx_object.lo_name);
td->td_proc->p_stats->p_ru.ru_nvcsw++;
mi_switch();
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR3(KTR_LOCK,
"_mtx_lock_sleep: p %p free from blocked on [%p] %s",
td, m, m->mtx_object.lo_name);
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, critical_t mtx_crit, const char *file,
int line)
{
int i = 0;
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR1(KTR_LOCK, "_mtx_lock_spin: %p spinning", m);
for (;;) {
if (_obtain_lock(m, curthread))
break;
/* Give interrupts a chance while we spin. */
critical_exit(mtx_crit);
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_object.lo_name, (void *)m->mtx_lock);
}
mtx_crit = critical_enter();
}
m->mtx_savecrit = mtx_crit;
if (LOCK_LOG_TEST(&m->mtx_object, opts))
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 thread *td, *td1;
struct mtx *m1;
int pri;
struct ksegrp *kg;
td = curthread;
kg = td->td_ksegrp;
if (mtx_recursed(m)) {
if (--(m->mtx_recurse) == 0)
atomic_clear_ptr(&m->mtx_lock, MTX_RECURSED);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p unrecurse", m);
return;
}
mtx_lock_spin(&sched_lock);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p contested", m);
td1 = TAILQ_FIRST(&m->mtx_blocked);
MPASS(td->td_proc->p_magic == P_MAGIC);
MPASS(td1->td_proc->p_magic == P_MAGIC);
TAILQ_REMOVE(&m->mtx_blocked, td1, td_blkq);
if (TAILQ_EMPTY(&m->mtx_blocked)) {
LIST_REMOVE(m, mtx_contested);
_release_lock_quick(m);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR1(KTR_LOCK, "_mtx_unlock_sleep: %p not held", m);
} else
atomic_store_rel_ptr(&m->mtx_lock, (void *)MTX_CONTESTED);
pri = PRI_MAX;
LIST_FOREACH(m1, &td->td_contested, mtx_contested) {
int cp = TAILQ_FIRST(&m1->mtx_blocked)->td_ksegrp->kg_pri.pri_level;
if (cp < pri)
pri = cp;
}
if (pri > kg->kg_pri.pri_native)
pri = kg->kg_pri.pri_native;
SET_PRIO(td, pri);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p contested setrunqueue %p",
m, td1);
td1->td_blocked = NULL;
td1->td_proc->p_stat = SRUN;
setrunqueue(td1);
if ((opts & MTX_NOSWITCH) == 0 && td1->td_ksegrp->kg_pri.pri_level < pri) {
#ifdef notyet
if (td->td_ithd != NULL) {
struct ithd *it = td->td_ithd;
if (it->it_interrupted) {
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR2(KTR_LOCK,
"_mtx_unlock_sleep: %p interrupted %p",
it, it->it_interrupted);
intr_thd_fixup(it);
}
}
#endif
setrunqueue(td);
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR2(KTR_LOCK,
"_mtx_unlock_sleep: %p switching out lock=%p", m,
(void *)m->mtx_lock);
td->td_proc->p_stats->p_ru.ru_nivcsw++;
mi_switch();
if (LOCK_LOG_TEST(&m->mtx_object, opts))
CTR2(KTR_LOCK, "_mtx_unlock_sleep: %p resuming lock=%p",
m, (void *)m->mtx_lock);
}
mtx_unlock_spin(&sched_lock);
return;
}
/*
* All the unlocking of MTX_SPIN locks is done inline.
* See the _rel_spin_lock() macro for the details.
*/
/*
* The backing function for the INVARIANTS-enabled mtx_assert()
*/
#ifdef INVARIANT_SUPPORT
void
_mtx_assert(struct mtx *m, int what, const char *file, int line)
{
if (panicstr != NULL)
return;
switch (what) {
case MA_OWNED:
case MA_OWNED | MA_RECURSED:
case MA_OWNED | MA_NOTRECURSED:
if (!mtx_owned(m))
panic("mutex %s not owned at %s:%d",
m->mtx_object.lo_name, file, line);
if (mtx_recursed(m)) {
if ((what & MA_NOTRECURSED) != 0)
panic("mutex %s recursed at %s:%d",
m->mtx_object.lo_name, file, line);
} else if ((what & MA_RECURSED) != 0) {
panic("mutex %s unrecursed at %s:%d",
m->mtx_object.lo_name, file, line);
}
break;
case MA_NOTOWNED:
if (mtx_owned(m))
panic("mutex %s owned at %s:%d",
m->mtx_object.lo_name, file, line);
break;
default:
panic("unknown mtx_assert at %s:%d", file, line);
}
}
#endif
/*
* The MUTEX_DEBUG-enabled mtx_validate()
*
* Most of these checks have been moved off into the LO_INITIALIZED flag
* maintained by the witness code.
*/
#ifdef MUTEX_DEBUG
void mtx_validate __P((struct mtx *));
void
mtx_validate(struct mtx *m)
{
/*
* XXX - When kernacc() is fixed on the alpha to handle K0_SEG memory properly
* we can re-enable the kernacc() checks.
*/
#ifndef __alpha__
/*
* Can't call kernacc() from early init386(), especially when
* initializing Giant mutex, because some stuff in kernacc()
* requires Giant itself.
*/
if (!cold)
if (!kernacc((caddr_t)m, sizeof(m),
VM_PROT_READ | VM_PROT_WRITE))
panic("Can't read and write to mutex %p", m);
#endif
}
#endif
/*
* Mutex initialization routine; initialize lock `m' of type contained in
* `opts' with options contained in `opts' and description `description.'
*/
void
mtx_init(struct mtx *m, const char *description, int opts)
{
struct lock_object *lock;
MPASS((opts & ~(MTX_SPIN | MTX_QUIET | MTX_RECURSE |
MTX_SLEEPABLE | MTX_NOWITNESS)) == 0);
#ifdef MUTEX_DEBUG
/* Diagnostic and error correction */
mtx_validate(m);
#endif
lock = &m->mtx_object;
KASSERT((lock->lo_flags & LO_INITIALIZED) == 0,
("mutex %s %p already initialized", description, m));
bzero(m, sizeof(*m));
if (opts & MTX_SPIN)
lock->lo_class = &lock_class_mtx_spin;
else
lock->lo_class = &lock_class_mtx_sleep;
lock->lo_name = description;
if (opts & MTX_QUIET)
lock->lo_flags = LO_QUIET;
if (opts & MTX_RECURSE)
lock->lo_flags |= LO_RECURSABLE;
if (opts & MTX_SLEEPABLE)
lock->lo_flags |= LO_SLEEPABLE;
if ((opts & MTX_NOWITNESS) == 0)
lock->lo_flags |= LO_WITNESS;
m->mtx_lock = MTX_UNOWNED;
TAILQ_INIT(&m->mtx_blocked);
LOCK_LOG_INIT(lock, opts);
WITNESS_INIT(lock);
}
/*
* Remove lock `m' from all_mtx queue. We don't allow MTX_QUIET to be
* passed in as a flag here because if the corresponding mtx_init() was
* called with MTX_QUIET set, then it will already be set in the mutex's
* flags.
*/
void
mtx_destroy(struct mtx *m)
{
LOCK_LOG_DESTROY(&m->mtx_object, 0);
if (!mtx_owned(m))
MPASS(mtx_unowned(m));
else {
MPASS((m->mtx_lock & (MTX_RECURSED|MTX_CONTESTED)) == 0);
/* Tell witness this isn't locked to make it happy. */
WITNESS_UNLOCK(&m->mtx_object, LOP_EXCLUSIVE | LOP_NOSWITCH,
__FILE__, __LINE__);
}
WITNESS_DESTROY(&m->mtx_object);
}
/*
* Encapsulated Giant mutex routines. These routines provide encapsulation
* control for the Giant mutex, allowing sysctls to be used to turn on and
* off Giant around certain subsystems. The default value for the sysctls
* are set to what developers believe is stable and working in regards to
* the Giant pushdown. Developers should not turn off Giant via these
* sysctls unless they know what they are doing.
*
* Callers of mtx_lock_giant() are expected to pass the return value to an
* accompanying mtx_unlock_giant() later on. If multiple subsystems are
* effected by a Giant wrap, all related sysctl variables must be zero for
* the subsystem call to operate without Giant (as determined by the caller).
*/
SYSCTL_NODE(_kern, OID_AUTO, giant, CTLFLAG_RD, NULL, "Giant mutex manipulation");
static int kern_giant_all = 0;
SYSCTL_INT(_kern_giant, OID_AUTO, all, CTLFLAG_RW, &kern_giant_all, 0, "");
int kern_giant_proc = 1; /* Giant around PROC locks */
int kern_giant_file = 1; /* Giant around struct file & filedesc */
SYSCTL_INT(_kern_giant, OID_AUTO, proc, CTLFLAG_RW, &kern_giant_proc, 0, "");
SYSCTL_INT(_kern_giant, OID_AUTO, file, CTLFLAG_RW, &kern_giant_file, 0, "");
int
mtx_lock_giant(int sysctlvar)
{
if (sysctlvar || kern_giant_all) {
mtx_lock(&Giant);
return(1);
}
return(0);
}
void
mtx_unlock_giant(int s)
{
if (s)
mtx_unlock(&Giant);
}