500 lines
12 KiB
C
500 lines
12 KiB
C
/* $NetBSD: kern_turnstile.c,v 1.10 2007/07/09 21:10:54 ad Exp $ */
|
|
|
|
/*-
|
|
* Copyright (c) 2002, 2006, 2007 The NetBSD Foundation, Inc.
|
|
* All rights reserved.
|
|
*
|
|
* This code is derived from software contributed to The NetBSD Foundation
|
|
* by Jason R. Thorpe and Andrew Doran.
|
|
*
|
|
* 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. All advertising materials mentioning features or use of this software
|
|
* must display the following acknowledgement:
|
|
* This product includes software developed by the NetBSD
|
|
* Foundation, Inc. and its contributors.
|
|
* 4. Neither the name of The NetBSD Foundation nor the names of its
|
|
* contributors may be used to endorse or promote products derived
|
|
* from this software without specific prior written permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
* ``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 FOUNDATION OR CONTRIBUTORS
|
|
* 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.
|
|
*/
|
|
|
|
/*
|
|
* Turnstiles are described in detail in:
|
|
*
|
|
* Solaris Internals: Core Kernel Architecture, Jim Mauro and
|
|
* Richard McDougall.
|
|
*
|
|
* Turnstiles are kept in a hash table. There are likely to be many more
|
|
* synchronisation objects than there are threads. Since a thread can block
|
|
* on only one lock at a time, we only need one turnstile per thread, and
|
|
* so they are allocated at thread creation time.
|
|
*
|
|
* When a thread decides it needs to block on a lock, it looks up the
|
|
* active turnstile for that lock. If no active turnstile exists, then
|
|
* the process lends its turnstile to the lock. If there is already an
|
|
* active turnstile for the lock, the thread places its turnstile on a
|
|
* list of free turnstiles, and references the active one instead.
|
|
*
|
|
* The act of looking up the turnstile acquires an interlock on the sleep
|
|
* queue. If a thread decides it doesn't need to block after all, then this
|
|
* interlock must be released by explicitly aborting the turnstile
|
|
* operation.
|
|
*
|
|
* When a thread is awakened, it needs to get its turnstile back. If there
|
|
* are still other threads waiting in the active turnstile, the the thread
|
|
* grabs a free turnstile off the free list. Otherwise, it can take back
|
|
* the active turnstile from the lock (thus deactivating the turnstile).
|
|
*
|
|
* Turnstiles are the place to do priority inheritence.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__KERNEL_RCSID(0, "$NetBSD: kern_turnstile.c,v 1.10 2007/07/09 21:10:54 ad Exp $");
|
|
|
|
#include <sys/param.h>
|
|
#include <sys/lock.h>
|
|
#include <sys/lockdebug.h>
|
|
#include <sys/pool.h>
|
|
#include <sys/proc.h>
|
|
#include <sys/sleepq.h>
|
|
#include <sys/systm.h>
|
|
|
|
#include <uvm/uvm_extern.h>
|
|
|
|
#define TS_HASH_SIZE 64
|
|
#define TS_HASH_MASK (TS_HASH_SIZE - 1)
|
|
#define TS_HASH(obj) (((uintptr_t)(obj) >> 3) & TS_HASH_MASK)
|
|
|
|
tschain_t turnstile_tab[TS_HASH_SIZE];
|
|
|
|
struct pool turnstile_pool;
|
|
struct pool_cache turnstile_cache;
|
|
|
|
int turnstile_ctor(void *, void *, int);
|
|
|
|
extern turnstile_t turnstile0;
|
|
|
|
/*
|
|
* turnstile_init:
|
|
*
|
|
* Initialize the turnstile mechanism.
|
|
*/
|
|
void
|
|
turnstile_init(void)
|
|
{
|
|
tschain_t *tc;
|
|
int i;
|
|
|
|
for (i = 0; i < TS_HASH_SIZE; i++) {
|
|
tc = &turnstile_tab[i];
|
|
LIST_INIT(&tc->tc_chain);
|
|
mutex_init(&tc->tc_mutex, MUTEX_SPIN, IPL_SCHED);
|
|
}
|
|
|
|
pool_init(&turnstile_pool, sizeof(turnstile_t), 0, 0, 0,
|
|
"tstilepl", &pool_allocator_nointr, IPL_NONE);
|
|
pool_cache_init(&turnstile_cache, &turnstile_pool,
|
|
turnstile_ctor, NULL, NULL);
|
|
|
|
(void)turnstile_ctor(NULL, &turnstile0, 0);
|
|
}
|
|
|
|
/*
|
|
* turnstile_ctor:
|
|
*
|
|
* Constructor for turnstiles.
|
|
*/
|
|
int
|
|
turnstile_ctor(void *arg, void *obj, int flags)
|
|
{
|
|
turnstile_t *ts = obj;
|
|
|
|
memset(ts, 0, sizeof(*ts));
|
|
sleepq_init(&ts->ts_sleepq[TS_READER_Q], NULL);
|
|
sleepq_init(&ts->ts_sleepq[TS_WRITER_Q], NULL);
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* turnstile_remove:
|
|
*
|
|
* Remove an LWP from a turnstile sleep queue and wake it.
|
|
*/
|
|
static inline void
|
|
turnstile_remove(turnstile_t *ts, lwp_t *l, sleepq_t *sq)
|
|
{
|
|
turnstile_t *nts;
|
|
|
|
KASSERT(l->l_ts == ts);
|
|
|
|
/*
|
|
* This process is no longer using the active turnstile.
|
|
* Find an inactive one on the free list to give to it.
|
|
*/
|
|
if ((nts = ts->ts_free) != NULL) {
|
|
KASSERT(TS_ALL_WAITERS(ts) > 1);
|
|
l->l_ts = nts;
|
|
ts->ts_free = nts->ts_free;
|
|
nts->ts_free = NULL;
|
|
} else {
|
|
/*
|
|
* If the free list is empty, this is the last
|
|
* waiter.
|
|
*/
|
|
KASSERT(TS_ALL_WAITERS(ts) == 1);
|
|
LIST_REMOVE(ts, ts_chain);
|
|
}
|
|
|
|
(void)sleepq_remove(sq, l);
|
|
}
|
|
|
|
/*
|
|
* turnstile_lookup:
|
|
*
|
|
* Look up the turnstile for the specified lock. This acquires and
|
|
* holds the turnstile chain lock (sleep queue interlock).
|
|
*/
|
|
turnstile_t *
|
|
turnstile_lookup(wchan_t obj)
|
|
{
|
|
turnstile_t *ts;
|
|
tschain_t *tc;
|
|
|
|
tc = &turnstile_tab[TS_HASH(obj)];
|
|
mutex_spin_enter(&tc->tc_mutex);
|
|
|
|
LIST_FOREACH(ts, &tc->tc_chain, ts_chain)
|
|
if (ts->ts_obj == obj)
|
|
return (ts);
|
|
|
|
/*
|
|
* No turnstile yet for this lock. No problem, turnstile_block()
|
|
* handles this by fetching the turnstile from the blocking thread.
|
|
*/
|
|
return (NULL);
|
|
}
|
|
|
|
/*
|
|
* turnstile_exit:
|
|
*
|
|
* Abort a turnstile operation.
|
|
*/
|
|
void
|
|
turnstile_exit(wchan_t obj)
|
|
{
|
|
tschain_t *tc;
|
|
|
|
tc = &turnstile_tab[TS_HASH(obj)];
|
|
mutex_spin_exit(&tc->tc_mutex);
|
|
}
|
|
|
|
/*
|
|
* turnstile_block:
|
|
*
|
|
* Enter an object into the turnstile chain and prepare the current
|
|
* LWP for sleep.
|
|
*/
|
|
void
|
|
turnstile_block(turnstile_t *ts, int q, wchan_t obj, syncobj_t *sobj)
|
|
{
|
|
lwp_t *l;
|
|
lwp_t *cur; /* cached curlwp */
|
|
lwp_t *owner;
|
|
turnstile_t *ots;
|
|
tschain_t *tc;
|
|
sleepq_t *sq;
|
|
pri_t prio;
|
|
|
|
tc = &turnstile_tab[TS_HASH(obj)];
|
|
l = cur = curlwp;
|
|
|
|
KASSERT(q == TS_READER_Q || q == TS_WRITER_Q);
|
|
KASSERT(mutex_owned(&tc->tc_mutex));
|
|
KASSERT(l != NULL && l->l_ts != NULL);
|
|
|
|
if (ts == NULL) {
|
|
/*
|
|
* We are the first thread to wait for this object;
|
|
* lend our turnstile to it.
|
|
*/
|
|
ts = l->l_ts;
|
|
KASSERT(TS_ALL_WAITERS(ts) == 0);
|
|
KASSERT(TAILQ_EMPTY(&ts->ts_sleepq[TS_READER_Q].sq_queue) &&
|
|
TAILQ_EMPTY(&ts->ts_sleepq[TS_WRITER_Q].sq_queue));
|
|
ts->ts_obj = obj;
|
|
ts->ts_inheritor = NULL;
|
|
ts->ts_sleepq[TS_READER_Q].sq_mutex = &tc->tc_mutex;
|
|
ts->ts_sleepq[TS_WRITER_Q].sq_mutex = &tc->tc_mutex;
|
|
LIST_INSERT_HEAD(&tc->tc_chain, ts, ts_chain);
|
|
} else {
|
|
/*
|
|
* Object already has a turnstile. Put our turnstile
|
|
* onto the free list, and reference the existing
|
|
* turnstile instead.
|
|
*/
|
|
ots = l->l_ts;
|
|
ots->ts_free = ts->ts_free;
|
|
ts->ts_free = ots;
|
|
l->l_ts = ts;
|
|
|
|
KASSERT(ts->ts_obj == obj);
|
|
KASSERT(TS_ALL_WAITERS(ts) != 0);
|
|
KASSERT(!TAILQ_EMPTY(&ts->ts_sleepq[TS_READER_Q].sq_queue) ||
|
|
!TAILQ_EMPTY(&ts->ts_sleepq[TS_WRITER_Q].sq_queue));
|
|
}
|
|
|
|
sq = &ts->ts_sleepq[q];
|
|
sleepq_enter(sq, l);
|
|
LOCKDEBUG_BARRIER(&tc->tc_mutex, 1);
|
|
l->l_priority = sched_kpri(l);
|
|
prio = lwp_eprio(l);
|
|
sleepq_enqueue(sq, prio, obj, "tstile", sobj);
|
|
|
|
/*
|
|
* lend our priority to lwps on the blocking chain.
|
|
*/
|
|
|
|
for (;;) {
|
|
bool dolock;
|
|
|
|
if (l->l_wchan == NULL)
|
|
break;
|
|
|
|
owner = (*l->l_syncobj->sobj_owner)(l->l_wchan);
|
|
if (owner == NULL)
|
|
break;
|
|
|
|
KASSERT(l != owner);
|
|
KASSERT(cur != owner);
|
|
|
|
if (l->l_mutex != owner->l_mutex)
|
|
dolock = true;
|
|
else
|
|
dolock = false;
|
|
if (dolock && !lwp_trylock(owner)) {
|
|
/*
|
|
* restart from curlwp.
|
|
*/
|
|
lwp_unlock(l);
|
|
l = cur;
|
|
lwp_lock(l);
|
|
prio = lwp_eprio(l);
|
|
continue;
|
|
}
|
|
if (prio >= lwp_eprio(owner)) {
|
|
if (dolock)
|
|
lwp_unlock(owner);
|
|
break;
|
|
}
|
|
ts = l->l_ts;
|
|
KASSERT(ts->ts_inheritor == owner || ts->ts_inheritor == NULL);
|
|
if (ts->ts_inheritor == NULL) {
|
|
ts->ts_inheritor = owner;
|
|
ts->ts_eprio = prio;
|
|
SLIST_INSERT_HEAD(&owner->l_pi_lenders, ts, ts_pichain);
|
|
lwp_lendpri(owner, prio);
|
|
} else if (prio < ts->ts_eprio) {
|
|
ts->ts_eprio = prio;
|
|
lwp_lendpri(owner, prio);
|
|
}
|
|
if (dolock)
|
|
lwp_unlock(l);
|
|
l = owner;
|
|
}
|
|
LOCKDEBUG_BARRIER(l->l_mutex, 1);
|
|
if (cur->l_mutex != l->l_mutex) {
|
|
lwp_unlock(l);
|
|
lwp_lock(cur);
|
|
}
|
|
LOCKDEBUG_BARRIER(cur->l_mutex, 1);
|
|
|
|
sleepq_block(0, false);
|
|
}
|
|
|
|
/*
|
|
* turnstile_wakeup:
|
|
*
|
|
* Wake up the specified number of threads that are blocked
|
|
* in a turnstile.
|
|
*/
|
|
void
|
|
turnstile_wakeup(turnstile_t *ts, int q, int count, lwp_t *nl)
|
|
{
|
|
sleepq_t *sq;
|
|
tschain_t *tc;
|
|
lwp_t *l;
|
|
|
|
tc = &turnstile_tab[TS_HASH(ts->ts_obj)];
|
|
sq = &ts->ts_sleepq[q];
|
|
|
|
KASSERT(q == TS_READER_Q || q == TS_WRITER_Q);
|
|
KASSERT(count > 0 && count <= TS_WAITERS(ts, q));
|
|
KASSERT(mutex_owned(&tc->tc_mutex) && sq->sq_mutex == &tc->tc_mutex);
|
|
KASSERT(ts->ts_inheritor == curlwp || ts->ts_inheritor == NULL);
|
|
|
|
/*
|
|
* restore inherited priority if necessary.
|
|
*/
|
|
|
|
if (ts->ts_inheritor != NULL) {
|
|
turnstile_t *iter;
|
|
turnstile_t *next;
|
|
turnstile_t *prev = NULL;
|
|
pri_t prio;
|
|
bool dolock;
|
|
|
|
ts->ts_inheritor = NULL;
|
|
l = curlwp;
|
|
|
|
dolock = l->l_mutex == &l->l_cpu->ci_schedstate.spc_lwplock;
|
|
if (dolock) {
|
|
lwp_lock(l);
|
|
}
|
|
|
|
/*
|
|
* the following loop does two things.
|
|
*
|
|
* - remove ts from the list.
|
|
*
|
|
* - from the rest of the list, find the highest priority.
|
|
*/
|
|
|
|
prio = MAXPRI;
|
|
KASSERT(!SLIST_EMPTY(&l->l_pi_lenders));
|
|
for (iter = SLIST_FIRST(&l->l_pi_lenders);
|
|
iter != NULL; iter = next) {
|
|
KASSERT(lwp_eprio(l) <= ts->ts_eprio);
|
|
next = SLIST_NEXT(iter, ts_pichain);
|
|
if (iter == ts) {
|
|
if (prev == NULL) {
|
|
SLIST_REMOVE_HEAD(&l->l_pi_lenders,
|
|
ts_pichain);
|
|
} else {
|
|
SLIST_REMOVE_AFTER(prev, ts_pichain);
|
|
}
|
|
} else if (prio > iter->ts_eprio) {
|
|
prio = iter->ts_eprio;
|
|
}
|
|
prev = iter;
|
|
}
|
|
|
|
lwp_lendpri(l, prio);
|
|
|
|
if (dolock) {
|
|
lwp_unlock(l);
|
|
}
|
|
}
|
|
|
|
if (nl != NULL) {
|
|
#if defined(DEBUG) || defined(LOCKDEBUG)
|
|
TAILQ_FOREACH(l, &sq->sq_queue, l_sleepchain) {
|
|
if (l == nl)
|
|
break;
|
|
}
|
|
if (l == NULL)
|
|
panic("turnstile_wakeup: nl not on sleepq");
|
|
#endif
|
|
turnstile_remove(ts, nl, sq);
|
|
} else {
|
|
while (count-- > 0) {
|
|
l = TAILQ_FIRST(&sq->sq_queue);
|
|
KASSERT(l != NULL);
|
|
turnstile_remove(ts, l, sq);
|
|
}
|
|
}
|
|
mutex_spin_exit(&tc->tc_mutex);
|
|
}
|
|
|
|
/*
|
|
* turnstile_unsleep:
|
|
*
|
|
* Remove an LWP from the turnstile. This is called when the LWP has
|
|
* not been awoken normally but instead interrupted: for example, if it
|
|
* has received a signal. It's not a valid action for turnstiles,
|
|
* since LWPs blocking on a turnstile are not interruptable.
|
|
*/
|
|
void
|
|
turnstile_unsleep(lwp_t *l)
|
|
{
|
|
|
|
lwp_unlock(l);
|
|
panic("turnstile_unsleep");
|
|
}
|
|
|
|
/*
|
|
* turnstile_changepri:
|
|
*
|
|
* Adjust the priority of an LWP residing on a turnstile.
|
|
*/
|
|
void
|
|
turnstile_changepri(lwp_t *l, pri_t pri)
|
|
{
|
|
|
|
/* XXX priority inheritance */
|
|
sleepq_changepri(l, pri);
|
|
}
|
|
|
|
#if defined(LOCKDEBUG)
|
|
/*
|
|
* turnstile_print:
|
|
*
|
|
* Given the address of a lock object, print the contents of a
|
|
* turnstile.
|
|
*/
|
|
void
|
|
turnstile_print(volatile void *obj, void (*pr)(const char *, ...))
|
|
{
|
|
turnstile_t *ts;
|
|
tschain_t *tc;
|
|
sleepq_t *rsq, *wsq;
|
|
lwp_t *l;
|
|
|
|
tc = &turnstile_tab[TS_HASH(obj)];
|
|
|
|
LIST_FOREACH(ts, &tc->tc_chain, ts_chain)
|
|
if (ts->ts_obj == obj)
|
|
break;
|
|
|
|
(*pr)("Turnstile chain at %p.\n", tc);
|
|
if (ts == NULL) {
|
|
(*pr)("=> No active turnstile for this lock.\n");
|
|
return;
|
|
}
|
|
|
|
rsq = &ts->ts_sleepq[TS_READER_Q];
|
|
wsq = &ts->ts_sleepq[TS_WRITER_Q];
|
|
|
|
(*pr)("=> Turnstile at %p (wrq=%p, rdq=%p).\n", ts, rsq, wsq);
|
|
|
|
(*pr)("=> %d waiting readers:", rsq->sq_waiters);
|
|
TAILQ_FOREACH(l, &rsq->sq_queue, l_sleepchain) {
|
|
(*pr)(" %p", l);
|
|
}
|
|
(*pr)("\n");
|
|
|
|
(*pr)("=> %d waiting writers:", wsq->sq_waiters);
|
|
TAILQ_FOREACH(l, &wsq->sq_queue, l_sleepchain) {
|
|
(*pr)(" %p", l);
|
|
}
|
|
(*pr)("\n");
|
|
}
|
|
#endif /* LOCKDEBUG */
|