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freebsd/sys/kern/kern_sx.c
Don Lewis 857d9c60d0 Extend the mutex pool implementation to permit the creation and use of
multiple mutex pools with different options and sizes.  Mutex pools can
be created with either the default sleep mutexes or with spin mutexes.
A dynamically created mutex pool can now be destroyed if it is no longer
needed.

Create two pools by default, one that matches the existing pool that
uses the MTX_NOWITNESS option that should be used for building higher
level locks, and a new pool with witness checking enabled.

Modify the users of the existing mutex pool to use the appropriate pool
in the new implementation.

Reviewed by:	jhb
2003-07-13 01:22:21 +00:00

350 lines
8.7 KiB
C

/*
* Copyright (C) 2001 Jason Evans <jasone@freebsd.org>. 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(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``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 THE COPYRIGHT HOLDER(S) 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.
*/
/*
* Shared/exclusive locks. This implementation assures deterministic lock
* granting behavior, so that slocks and xlocks are interleaved.
*
* Priority propagation will not generally raise the priority of lock holders,
* so should not be relied upon in combination with sx locks.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/ktr.h>
#include <sys/condvar.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/sx.h>
struct lock_class lock_class_sx = {
"sx",
LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE
};
#ifndef INVARIANTS
#define _sx_assert(sx, what, file, line)
#endif
void
sx_sysinit(void *arg)
{
struct sx_args *sargs = arg;
sx_init(sargs->sa_sx, sargs->sa_desc);
}
void
sx_init(struct sx *sx, const char *description)
{
struct lock_object *lock;
lock = &sx->sx_object;
KASSERT((lock->lo_flags & LO_INITIALIZED) == 0,
("sx lock %s %p already initialized", description, sx));
bzero(sx, sizeof(*sx));
lock->lo_class = &lock_class_sx;
lock->lo_type = lock->lo_name = description;
lock->lo_flags = LO_WITNESS | LO_RECURSABLE | LO_SLEEPABLE |
LO_UPGRADABLE;
sx->sx_lock = mtx_pool_find(mtxpool_lockbuilder, sx);
sx->sx_cnt = 0;
cv_init(&sx->sx_shrd_cv, description);
sx->sx_shrd_wcnt = 0;
cv_init(&sx->sx_excl_cv, description);
sx->sx_excl_wcnt = 0;
sx->sx_xholder = NULL;
LOCK_LOG_INIT(lock, 0);
WITNESS_INIT(lock);
}
void
sx_destroy(struct sx *sx)
{
LOCK_LOG_DESTROY(&sx->sx_object, 0);
KASSERT((sx->sx_cnt == 0 && sx->sx_shrd_wcnt == 0 && sx->sx_excl_wcnt ==
0), ("%s (%s): holders or waiters\n", __func__,
sx->sx_object.lo_name));
sx->sx_lock = NULL;
cv_destroy(&sx->sx_shrd_cv);
cv_destroy(&sx->sx_excl_cv);
WITNESS_DESTROY(&sx->sx_object);
}
void
_sx_slock(struct sx *sx, const char *file, int line)
{
mtx_lock(sx->sx_lock);
KASSERT(sx->sx_xholder != curthread,
("%s (%s): slock while xlock is held @ %s:%d\n", __func__,
sx->sx_object.lo_name, file, line));
/*
* Loop in case we lose the race for lock acquisition.
*/
while (sx->sx_cnt < 0) {
sx->sx_shrd_wcnt++;
cv_wait(&sx->sx_shrd_cv, sx->sx_lock);
sx->sx_shrd_wcnt--;
}
/* Acquire a shared lock. */
sx->sx_cnt++;
LOCK_LOG_LOCK("SLOCK", &sx->sx_object, 0, 0, file, line);
WITNESS_LOCK(&sx->sx_object, 0, file, line);
mtx_unlock(sx->sx_lock);
}
int
_sx_try_slock(struct sx *sx, const char *file, int line)
{
mtx_lock(sx->sx_lock);
if (sx->sx_cnt >= 0) {
sx->sx_cnt++;
LOCK_LOG_TRY("SLOCK", &sx->sx_object, 0, 1, file, line);
WITNESS_LOCK(&sx->sx_object, LOP_TRYLOCK, file, line);
mtx_unlock(sx->sx_lock);
return (1);
} else {
LOCK_LOG_TRY("SLOCK", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
return (0);
}
}
void
_sx_xlock(struct sx *sx, const char *file, int line)
{
mtx_lock(sx->sx_lock);
/*
* With sx locks, we're absolutely not permitted to recurse on
* xlocks, as it is fatal (deadlock). Normally, recursion is handled
* by WITNESS, but as it is not semantically correct to hold the
* xlock while in here, we consider it API abuse and put it under
* INVARIANTS.
*/
KASSERT(sx->sx_xholder != curthread,
("%s (%s): xlock already held @ %s:%d", __func__,
sx->sx_object.lo_name, file, line));
/* Loop in case we lose the race for lock acquisition. */
while (sx->sx_cnt != 0) {
sx->sx_excl_wcnt++;
cv_wait(&sx->sx_excl_cv, sx->sx_lock);
sx->sx_excl_wcnt--;
}
MPASS(sx->sx_cnt == 0);
/* Acquire an exclusive lock. */
sx->sx_cnt--;
sx->sx_xholder = curthread;
LOCK_LOG_LOCK("XLOCK", &sx->sx_object, 0, 0, file, line);
WITNESS_LOCK(&sx->sx_object, LOP_EXCLUSIVE, file, line);
mtx_unlock(sx->sx_lock);
}
int
_sx_try_xlock(struct sx *sx, const char *file, int line)
{
mtx_lock(sx->sx_lock);
if (sx->sx_cnt == 0) {
sx->sx_cnt--;
sx->sx_xholder = curthread;
LOCK_LOG_TRY("XLOCK", &sx->sx_object, 0, 1, file, line);
WITNESS_LOCK(&sx->sx_object, LOP_EXCLUSIVE | LOP_TRYLOCK, file,
line);
mtx_unlock(sx->sx_lock);
return (1);
} else {
LOCK_LOG_TRY("XLOCK", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
return (0);
}
}
void
_sx_sunlock(struct sx *sx, const char *file, int line)
{
_sx_assert(sx, SX_SLOCKED, file, line);
mtx_lock(sx->sx_lock);
WITNESS_UNLOCK(&sx->sx_object, 0, file, line);
/* Release. */
sx->sx_cnt--;
/*
* If we just released the last shared lock, wake any waiters up, giving
* exclusive lockers precedence. In order to make sure that exclusive
* lockers won't be blocked forever, don't wake shared lock waiters if
* there are exclusive lock waiters.
*/
if (sx->sx_excl_wcnt > 0) {
if (sx->sx_cnt == 0)
cv_signal(&sx->sx_excl_cv);
} else if (sx->sx_shrd_wcnt > 0)
cv_broadcast(&sx->sx_shrd_cv);
LOCK_LOG_LOCK("SUNLOCK", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
}
void
_sx_xunlock(struct sx *sx, const char *file, int line)
{
_sx_assert(sx, SX_XLOCKED, file, line);
mtx_lock(sx->sx_lock);
MPASS(sx->sx_cnt == -1);
WITNESS_UNLOCK(&sx->sx_object, LOP_EXCLUSIVE, file, line);
/* Release. */
sx->sx_cnt++;
sx->sx_xholder = NULL;
/*
* Wake up waiters if there are any. Give precedence to slock waiters.
*/
if (sx->sx_shrd_wcnt > 0)
cv_broadcast(&sx->sx_shrd_cv);
else if (sx->sx_excl_wcnt > 0)
cv_signal(&sx->sx_excl_cv);
LOCK_LOG_LOCK("XUNLOCK", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
}
int
_sx_try_upgrade(struct sx *sx, const char *file, int line)
{
_sx_assert(sx, SX_SLOCKED, file, line);
mtx_lock(sx->sx_lock);
if (sx->sx_cnt == 1) {
sx->sx_cnt = -1;
sx->sx_xholder = curthread;
LOCK_LOG_TRY("XUPGRADE", &sx->sx_object, 0, 1, file, line);
WITNESS_UPGRADE(&sx->sx_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
file, line);
mtx_unlock(sx->sx_lock);
return (1);
} else {
LOCK_LOG_TRY("XUPGRADE", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
return (0);
}
}
void
_sx_downgrade(struct sx *sx, const char *file, int line)
{
_sx_assert(sx, SX_XLOCKED, file, line);
mtx_lock(sx->sx_lock);
MPASS(sx->sx_cnt == -1);
WITNESS_DOWNGRADE(&sx->sx_object, 0, file, line);
sx->sx_cnt = 1;
sx->sx_xholder = NULL;
if (sx->sx_shrd_wcnt > 0)
cv_broadcast(&sx->sx_shrd_cv);
LOCK_LOG_LOCK("XDOWNGRADE", &sx->sx_object, 0, 0, file, line);
mtx_unlock(sx->sx_lock);
}
#ifdef INVARIANT_SUPPORT
#ifndef INVARIANTS
#undef _sx_assert
#endif
/*
* In the non-WITNESS case, sx_assert() can only detect that at least
* *some* thread owns an slock, but it cannot guarantee that *this*
* thread owns an slock.
*/
void
_sx_assert(struct sx *sx, int what, const char *file, int line)
{
switch (what) {
case SX_LOCKED:
case SX_SLOCKED:
#ifdef WITNESS
witness_assert(&sx->sx_object, what, file, line);
#else
mtx_lock(sx->sx_lock);
if (sx->sx_cnt <= 0 &&
(what == SX_SLOCKED || sx->sx_xholder != curthread))
printf("Lock %s not %slocked @ %s:%d\n",
sx->sx_object.lo_name, (what == SX_SLOCKED) ?
"share " : "", file, line);
mtx_unlock(sx->sx_lock);
#endif
break;
case SX_XLOCKED:
mtx_lock(sx->sx_lock);
if (sx->sx_xholder != curthread)
printf("Lock %s not exclusively locked @ %s:%d\n",
sx->sx_object.lo_name, file, line);
mtx_unlock(sx->sx_lock);
break;
default:
panic("Unknown sx lock assertion: %d @ %s:%d", what, file,
line);
}
}
#endif /* INVARIANT_SUPPORT */