FreeBSD-5.3/sys/kern/subr_sleepqueue.c
/*
* Copyright (c) 2004 John Baldwin <jhb@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, 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. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*/
/*
* Implementation of sleep queues used to hold queue of threads blocked on
* a wait channel. Sleep queues different from turnstiles in that wait
* channels are not owned by anyone, so there is no priority propagation.
* Sleep queues can also provide a timeout and can also be interrupted by
* signals. That said, there are several similarities between the turnstile
* and sleep queue implementations. (Note: turnstiles were implemented
* first.) For example, both use a hash table of the same size where each
* bucket is referred to as a "chain" that contains both a spin lock and
* a linked list of queues. An individual queue is located by using a hash
* to pick a chain, locking the chain, and then walking the chain searching
* for the queue. This means that a wait channel object does not need to
* embed it's queue head just as locks do not embed their turnstile queue
* head. Threads also carry around a sleep queue that they lend to the
* wait channel when blocking. Just as in turnstiles, the queue includes
* a free list of the sleep queues of other threads blocked on the same
* wait channel in the case of multiple waiters.
*
* Some additional functionality provided by sleep queues include the
* ability to set a timeout. The timeout is managed using a per-thread
* callout that resumes a thread if it is asleep. A thread may also
* catch signals while it is asleep (aka an interruptible sleep). The
* signal code uses sleepq_abort() to interrupt a sleeping thread. Finally,
* sleep queues also provide some extra assertions. One is not allowed to
* mix the sleep/wakeup and cv APIs for a given wait channel. Also, one
* must consistently use the same lock to synchronize with a wait channel,
* though this check is currently only a warning for sleep/wakeup due to
* pre-existing abuse of that API. The same lock must also be held when
* awakening threads, though that is currently only enforced for condition
* variables.
*/
#include "opt_sleepqueue_profiling.h"
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: src/sys/kern/subr_sleepqueue.c,v 1.10.2.2 2004/10/16 02:17:54 ups Exp $");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sched.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/sysctl.h>
/*
* Constants for the hash table of sleep queue chains. These constants are
* the same ones that 4BSD (and possibly earlier versions of BSD) used.
* Basically, we ignore the lower 8 bits of the address since most wait
* channel pointers are aligned and only look at the next 7 bits for the
* hash. SC_TABLESIZE must be a power of two for SC_MASK to work properly.
*/
#define SC_TABLESIZE 128 /* Must be power of 2. */
#define SC_MASK (SC_TABLESIZE - 1)
#define SC_SHIFT 8
#define SC_HASH(wc) (((uintptr_t)(wc) >> SC_SHIFT) & SC_MASK)
#define SC_LOOKUP(wc) &sleepq_chains[SC_HASH(wc)]
/*
* There two different lists of sleep queues. Both lists are connected
* via the sq_hash entries. The first list is the sleep queue chain list
* that a sleep queue is on when it is attached to a wait channel. The
* second list is the free list hung off of a sleep queue that is attached
* to a wait channel.
*
* Each sleep queue also contains the wait channel it is attached to, the
* list of threads blocked on that wait channel, flags specific to the
* wait channel, and the lock used to synchronize with a wait channel.
* The flags are used to catch mismatches between the various consumers
* of the sleep queue API (e.g. sleep/wakeup and condition variables).
* The lock pointer is only used when invariants are enabled for various
* debugging checks.
*
* Locking key:
* c - sleep queue chain lock
*/
struct sleepqueue {
TAILQ_HEAD(, thread) sq_blocked; /* (c) Blocked threads. */
LIST_ENTRY(sleepqueue) sq_hash; /* (c) Chain and free list. */
LIST_HEAD(, sleepqueue) sq_free; /* (c) Free queues. */
void *sq_wchan; /* (c) Wait channel. */
int sq_type; /* (c) Queue type. */
#ifdef INVARIANTS
struct mtx *sq_lock; /* (c) Associated lock. */
#endif
};
struct sleepqueue_chain {
LIST_HEAD(, sleepqueue) sc_queues; /* List of sleep queues. */
struct mtx sc_lock; /* Spin lock for this chain. */
#ifdef SLEEPQUEUE_PROFILING
u_int sc_depth; /* Length of sc_queues. */
u_int sc_max_depth; /* Max length of sc_queues. */
#endif
};
#ifdef SLEEPQUEUE_PROFILING
u_int sleepq_max_depth;
SYSCTL_NODE(_debug, OID_AUTO, sleepq, CTLFLAG_RD, 0, "sleepq profiling");
SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
"sleepq chain stats");
SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
0, "maxmimum depth achieved of a single chain");
#endif
static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
MALLOC_DEFINE(M_SLEEPQUEUE, "sleep queues", "sleep queues");
/*
* Prototypes for non-exported routines.
*/
static int sleepq_check_timeout(void);
static void sleepq_switch(void *wchan);
static void sleepq_timeout(void *arg);
static void sleepq_remove_thread(struct sleepqueue *sq, struct thread *td);
static void sleepq_resume_thread(struct thread *td, int pri);
/*
* Early initialization of sleep queues that is called from the sleepinit()
* SYSINIT.
*/
void
init_sleepqueues(void)
{
#ifdef SLEEPQUEUE_PROFILING
struct sysctl_oid *chain_oid;
char chain_name[10];
#endif
int i;
for (i = 0; i < SC_TABLESIZE; i++) {
LIST_INIT(&sleepq_chains[i].sc_queues);
mtx_init(&sleepq_chains[i].sc_lock, "sleepq chain", NULL,
MTX_SPIN);
#ifdef SLEEPQUEUE_PROFILING
snprintf(chain_name, sizeof(chain_name), "%d", i);
chain_oid = SYSCTL_ADD_NODE(NULL,
SYSCTL_STATIC_CHILDREN(_debug_sleepq_chains), OID_AUTO,
chain_name, CTLFLAG_RD, NULL, "sleepq chain stats");
SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
"depth", CTLFLAG_RD, &sleepq_chains[i].sc_depth, 0, NULL);
SYSCTL_ADD_UINT(NULL, SYSCTL_CHILDREN(chain_oid), OID_AUTO,
"max_depth", CTLFLAG_RD, &sleepq_chains[i].sc_max_depth, 0,
NULL);
#endif
}
thread0.td_sleepqueue = sleepq_alloc();
}
/*
* Malloc and initialize a new sleep queue for a new thread.
*/
struct sleepqueue *
sleepq_alloc(void)
{
struct sleepqueue *sq;
sq = malloc(sizeof(struct sleepqueue), M_SLEEPQUEUE, M_WAITOK | M_ZERO);
TAILQ_INIT(&sq->sq_blocked);
LIST_INIT(&sq->sq_free);
return (sq);
}
/*
* Free a sleep queue when a thread is destroyed.
*/
void
sleepq_free(struct sleepqueue *sq)
{
MPASS(sq != NULL);
MPASS(TAILQ_EMPTY(&sq->sq_blocked));
free(sq, M_SLEEPQUEUE);
}
/*
* Look up the sleep queue associated with a given wait channel in the hash
* table locking the associated sleep queue chain. Return holdind the sleep
* queue chain lock. If no queue is found in the table, NULL is returned.
*/
struct sleepqueue *
sleepq_lookup(void *wchan)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
sc = SC_LOOKUP(wchan);
mtx_lock_spin(&sc->sc_lock);
LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
if (sq->sq_wchan == wchan)
return (sq);
return (NULL);
}
/*
* Unlock the sleep queue chain associated with a given wait channel.
*/
void
sleepq_release(void *wchan)
{
struct sleepqueue_chain *sc;
sc = SC_LOOKUP(wchan);
mtx_unlock_spin(&sc->sc_lock);
}
/*
* Places the current thread on the sleepqueue for the specified wait
* channel. If INVARIANTS is enabled, then it associates the passed in
* lock with the sleepq to make sure it is held when that sleep queue is
* woken up.
*/
void
sleepq_add(struct sleepqueue *sq, void *wchan, struct mtx *lock,
const char *wmesg, int flags)
{
struct sleepqueue_chain *sc;
struct thread *td, *td1;
td = curthread;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
MPASS(td->td_sleepqueue != NULL);
MPASS(wchan != NULL);
/* If the passed in sleep queue is NULL, use this thread's queue. */
if (sq == NULL) {
#ifdef SLEEPQUEUE_PROFILING
sc->sc_depth++;
if (sc->sc_depth > sc->sc_max_depth) {
sc->sc_max_depth = sc->sc_depth;
if (sc->sc_max_depth > sleepq_max_depth)
sleepq_max_depth = sc->sc_max_depth;
}
#endif
sq = td->td_sleepqueue;
LIST_INSERT_HEAD(&sc->sc_queues, sq, sq_hash);
KASSERT(TAILQ_EMPTY(&sq->sq_blocked),
("thread's sleep queue has a non-empty queue"));
KASSERT(LIST_EMPTY(&sq->sq_free),
("thread's sleep queue has a non-empty free list"));
KASSERT(sq->sq_wchan == NULL, ("stale sq_wchan pointer"));
sq->sq_wchan = wchan;
#ifdef INVARIANTS
sq->sq_lock = lock;
#endif
sq->sq_type = flags & SLEEPQ_TYPE;
TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
} else {
MPASS(wchan == sq->sq_wchan);
MPASS(lock == sq->sq_lock);
TAILQ_FOREACH(td1, &sq->sq_blocked, td_slpq)
if (td1->td_priority > td->td_priority)
break;
if (td1 != NULL)
TAILQ_INSERT_BEFORE(td1, td, td_slpq);
else
TAILQ_INSERT_TAIL(&sq->sq_blocked, td, td_slpq);
LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
}
td->td_sleepqueue = NULL;
mtx_lock_spin(&sched_lock);
td->td_wchan = wchan;
td->td_wmesg = wmesg;
if (flags & SLEEPQ_INTERRUPTIBLE)
td->td_flags |= TDF_SINTR;
mtx_unlock_spin(&sched_lock);
}
/*
* Sets a timeout that will remove the current thread from the specified
* sleep queue after timo ticks if the thread has not already been awakened.
*/
void
sleepq_set_timeout(void *wchan, int timo)
{
struct sleepqueue_chain *sc;
struct thread *td;
td = curthread;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
MPASS(TD_ON_SLEEPQ(td));
MPASS(td->td_sleepqueue == NULL);
MPASS(wchan != NULL);
callout_reset(&td->td_slpcallout, timo, sleepq_timeout, td);
}
/*
* Marks the pending sleep of the current thread as interruptible and
* makes an initial check for pending signals before putting a thread
* to sleep.
*/
int
sleepq_catch_signals(void *wchan)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
struct thread *td;
struct proc *p;
int do_upcall;
int sig;
do_upcall = 0;
td = curthread;
p = td->td_proc;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
MPASS(td->td_sleepqueue == NULL);
MPASS(wchan != NULL);
CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
(void *)td, (long)p->p_pid, p->p_comm);
/* Mark thread as being in an interruptible sleep. */
MPASS(td->td_flags & TDF_SINTR);
MPASS(TD_ON_SLEEPQ(td));
sleepq_release(wchan);
/* See if there are any pending signals for this thread. */
PROC_LOCK(p);
mtx_lock(&p->p_sigacts->ps_mtx);
sig = cursig(td);
mtx_unlock(&p->p_sigacts->ps_mtx);
if (sig == 0 && thread_suspend_check(1))
sig = SIGSTOP;
else
do_upcall = thread_upcall_check(td);
PROC_UNLOCK(p);
/*
* If there were pending signals and this thread is still on
* the sleep queue, remove it from the sleep queue. If the
* thread was removed from the sleep queue while we were blocked
* above, then clear TDF_SINTR before returning.
*/
sq = sleepq_lookup(wchan);
mtx_lock_spin(&sched_lock);
if (TD_ON_SLEEPQ(td) && (sig != 0 || do_upcall != 0)) {
mtx_unlock_spin(&sched_lock);
sleepq_remove_thread(sq, td);
} else {
if (!TD_ON_SLEEPQ(td) && sig == 0)
td->td_flags &= ~TDF_SINTR;
mtx_unlock_spin(&sched_lock);
}
return (sig);
}
/*
* Switches to another thread if we are still asleep on a sleep queue and
* drop the lock on the sleepqueue chain. Returns with sched_lock held.
*/
static void
sleepq_switch(void *wchan)
{
struct sleepqueue_chain *sc;
struct thread *td;
td = curthread;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
/*
* If we have a sleep queue, then we've already been woken up, so
* just return.
*/
if (td->td_sleepqueue != NULL) {
MPASS(!TD_ON_SLEEPQ(td));
mtx_unlock_spin(&sc->sc_lock);
mtx_lock_spin(&sched_lock);
return;
}
/*
* Otherwise, actually go to sleep.
*/
mtx_lock_spin(&sched_lock);
mtx_unlock_spin(&sc->sc_lock);
sched_sleep(td);
TD_SET_SLEEPING(td);
mi_switch(SW_VOL, NULL);
KASSERT(TD_IS_RUNNING(td), ("running but not TDS_RUNNING"));
CTR3(KTR_PROC, "sleepq resume: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
}
/*
* Check to see if we timed out.
*/
static int
sleepq_check_timeout(void)
{
struct thread *td;
mtx_assert(&sched_lock, MA_OWNED);
td = curthread;
/*
* If TDF_TIMEOUT is set, we timed out.
*/
if (td->td_flags & TDF_TIMEOUT) {
td->td_flags &= ~TDF_TIMEOUT;
return (EWOULDBLOCK);
}
/*
* If TDF_TIMOFAIL is set, the timeout ran after we had
* already been woken up.
*/
if (td->td_flags & TDF_TIMOFAIL)
td->td_flags &= ~TDF_TIMOFAIL;
/*
* If callout_stop() fails, then the timeout is running on
* another CPU, so synchronize with it to avoid having it
* accidentally wake up a subsequent sleep.
*/
else if (callout_stop(&td->td_slpcallout) == 0) {
td->td_flags |= TDF_TIMEOUT;
TD_SET_SLEEPING(td);
mi_switch(SW_INVOL, NULL);
}
return (0);
}
/*
* Check to see if we were awoken by a signal.
*/
static int
sleepq_check_signals(void)
{
struct thread *td;
mtx_assert(&sched_lock, MA_OWNED);
td = curthread;
/*
* If TDF_SINTR is clear, then we were awakened while executing
* sleepq_catch_signals().
*/
if (!(td->td_flags & TDF_SINTR))
return (0);
/* We are no longer in an interruptible sleep. */
td->td_flags &= ~TDF_SINTR;
if (td->td_flags & TDF_INTERRUPT)
return (td->td_intrval);
return (0);
}
/*
* If we were in an interruptible sleep and we weren't interrupted and
* didn't timeout, check to see if there are any pending signals and
* which return value we should use if so. The return value from an
* earlier call to sleepq_catch_signals() should be passed in as the
* argument.
*/
int
sleepq_calc_signal_retval(int sig)
{
struct thread *td;
struct proc *p;
int rval;
td = curthread;
p = td->td_proc;
PROC_LOCK(p);
mtx_lock(&p->p_sigacts->ps_mtx);
/* XXX: Should we always be calling cursig()? */
if (sig == 0)
sig = cursig(td);
if (sig != 0) {
if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
rval = EINTR;
else
rval = ERESTART;
} else
rval = 0;
mtx_unlock(&p->p_sigacts->ps_mtx);
PROC_UNLOCK(p);
return (rval);
}
/*
* Block the current thread until it is awakened from its sleep queue.
*/
void
sleepq_wait(void *wchan)
{
MPASS(!(curthread->td_flags & TDF_SINTR));
sleepq_switch(wchan);
mtx_unlock_spin(&sched_lock);
}
/*
* Block the current thread until it is awakened from its sleep queue
* or it is interrupted by a signal.
*/
int
sleepq_wait_sig(void *wchan)
{
int rval;
sleepq_switch(wchan);
rval = sleepq_check_signals();
mtx_unlock_spin(&sched_lock);
return (rval);
}
/*
* Block the current thread until it is awakened from its sleep queue
* or it times out while waiting.
*/
int
sleepq_timedwait(void *wchan)
{
int rval;
MPASS(!(curthread->td_flags & TDF_SINTR));
sleepq_switch(wchan);
rval = sleepq_check_timeout();
mtx_unlock_spin(&sched_lock);
return (rval);
}
/*
* Block the current thread until it is awakened from its sleep queue,
* it is interrupted by a signal, or it times out waiting to be awakened.
*/
int
sleepq_timedwait_sig(void *wchan, int signal_caught)
{
int rvalt, rvals;
sleepq_switch(wchan);
rvalt = sleepq_check_timeout();
rvals = sleepq_check_signals();
mtx_unlock_spin(&sched_lock);
if (signal_caught || rvalt == 0)
return (rvals);
else
return (rvalt);
}
/*
* Removes a thread from a sleep queue.
*/
static void
sleepq_remove_thread(struct sleepqueue *sq, struct thread *td)
{
struct sleepqueue_chain *sc;
MPASS(td != NULL);
MPASS(sq->sq_wchan != NULL);
MPASS(td->td_wchan == sq->sq_wchan);
sc = SC_LOOKUP(sq->sq_wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
/* Remove the thread from the queue. */
TAILQ_REMOVE(&sq->sq_blocked, td, td_slpq);
/*
* Get a sleep queue for this thread. If this is the last waiter,
* use the queue itself and take it out of the chain, otherwise,
* remove a queue from the free list.
*/
if (LIST_EMPTY(&sq->sq_free)) {
td->td_sleepqueue = sq;
#ifdef INVARIANTS
sq->sq_wchan = NULL;
#endif
#ifdef SLEEPQUEUE_PROFILING
sc->sc_depth--;
#endif
} else
td->td_sleepqueue = LIST_FIRST(&sq->sq_free);
LIST_REMOVE(td->td_sleepqueue, sq_hash);
mtx_lock_spin(&sched_lock);
td->td_wmesg = NULL;
td->td_wchan = NULL;
mtx_unlock_spin(&sched_lock);
}
/*
* Resumes a thread that was asleep on a queue.
*/
static void
sleepq_resume_thread(struct thread *td, int pri)
{
/*
* Note that thread td might not be sleeping if it is running
* sleepq_catch_signals() on another CPU or is blocked on
* its proc lock to check signals. It doesn't hurt to clear
* the sleeping flag if it isn't set though, so we just always
* do it. However, we can't assert that it is set.
*/
mtx_lock_spin(&sched_lock);
CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, td->td_proc->p_comm);
TD_CLR_SLEEPING(td);
/* Adjust priority if requested. */
MPASS(pri == -1 || (pri >= PRI_MIN && pri <= PRI_MAX));
if (pri != -1 && td->td_priority > pri)
sched_prio(td, pri);
setrunnable(td);
mtx_unlock_spin(&sched_lock);
}
/*
* Find the highest priority thread sleeping on a wait channel and resume it.
*/
void
sleepq_signal(void *wchan, int flags, int pri)
{
struct sleepqueue *sq;
struct thread *td;
CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
sq = sleepq_lookup(wchan);
if (sq == NULL) {
sleepq_release(wchan);
return;
}
KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
("%s: mismatch between sleep/wakeup and cv_*", __func__));
/* XXX: Do for all sleep queues eventually. */
if (flags & SLEEPQ_CONDVAR)
mtx_assert(sq->sq_lock, MA_OWNED);
/* Remove first thread from queue and awaken it. */
td = TAILQ_FIRST(&sq->sq_blocked);
sleepq_remove_thread(sq, td);
sleepq_release(wchan);
sleepq_resume_thread(td, pri);
}
/*
* Resume all threads sleeping on a specified wait channel.
*/
void
sleepq_broadcast(void *wchan, int flags, int pri)
{
TAILQ_HEAD(, thread) list;
struct sleepqueue *sq;
struct thread *td;
CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
sq = sleepq_lookup(wchan);
if (sq == NULL) {
sleepq_release(wchan);
return;
}
KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
("%s: mismatch between sleep/wakeup and cv_*", __func__));
/* XXX: Do for all sleep queues eventually. */
if (flags & SLEEPQ_CONDVAR)
mtx_assert(sq->sq_lock, MA_OWNED);
/* Move blocked threads from the sleep queue to a temporary list. */
TAILQ_INIT(&list);
while (!TAILQ_EMPTY(&sq->sq_blocked)) {
td = TAILQ_FIRST(&sq->sq_blocked);
sleepq_remove_thread(sq, td);
TAILQ_INSERT_TAIL(&list, td, td_slpq);
}
sleepq_release(wchan);
/* Resume all the threads on the temporary list. */
while (!TAILQ_EMPTY(&list)) {
td = TAILQ_FIRST(&list);
TAILQ_REMOVE(&list, td, td_slpq);
sleepq_resume_thread(td, pri);
}
}
/*
* Time sleeping threads out. When the timeout expires, the thread is
* removed from the sleep queue and made runnable if it is still asleep.
*/
static void
sleepq_timeout(void *arg)
{
struct sleepqueue *sq;
struct thread *td;
void *wchan;
td = arg;
CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
/*
* First, see if the thread is asleep and get the wait channel if
* it is.
*/
mtx_lock_spin(&sched_lock);
if (TD_ON_SLEEPQ(td)) {
wchan = td->td_wchan;
mtx_unlock_spin(&sched_lock);
sq = sleepq_lookup(wchan);
mtx_lock_spin(&sched_lock);
} else {
wchan = NULL;
sq = NULL;
}
/*
* At this point, if the thread is still on the sleep queue,
* we have that sleep queue locked as it cannot migrate sleep
* queues while we dropped sched_lock. If it had resumed and
* was on another CPU while the lock was dropped, it would have
* seen that TDF_TIMEOUT and TDF_TIMOFAIL are clear and the
* call to callout_stop() to stop this routine would have failed
* meaning that it would have already set TDF_TIMEOUT to
* synchronize with this function.
*/
if (TD_ON_SLEEPQ(td)) {
MPASS(td->td_wchan == wchan);
MPASS(sq != NULL);
td->td_flags |= TDF_TIMEOUT;
mtx_unlock_spin(&sched_lock);
sleepq_remove_thread(sq, td);
sleepq_release(wchan);
sleepq_resume_thread(td, -1);
return;
} else if (wchan != NULL)
sleepq_release(wchan);
/*
* Now check for the edge cases. First, if TDF_TIMEOUT is set,
* then the other thread has already yielded to us, so clear
* the flag and resume it. If TDF_TIMEOUT is not set, then the
* we know that the other thread is not on a sleep queue, but it
* hasn't resumed execution yet. In that case, set TDF_TIMOFAIL
* to let it know that the timeout has already run and doesn't
* need to be canceled.
*/
if (td->td_flags & TDF_TIMEOUT) {
MPASS(TD_IS_SLEEPING(td));
td->td_flags &= ~TDF_TIMEOUT;
TD_CLR_SLEEPING(td);
setrunnable(td);
} else
td->td_flags |= TDF_TIMOFAIL;
mtx_unlock_spin(&sched_lock);
}
/*
* Resumes a specific thread from the sleep queue associated with a specific
* wait channel if it is on that queue.
*/
void
sleepq_remove(struct thread *td, void *wchan)
{
struct sleepqueue *sq;
/*
* Look up the sleep queue for this wait channel, then re-check
* that the thread is asleep on that channel, if it is not, then
* bail.
*/
MPASS(wchan != NULL);
sq = sleepq_lookup(wchan);
mtx_lock_spin(&sched_lock);
if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
mtx_unlock_spin(&sched_lock);
sleepq_release(wchan);
return;
}
mtx_unlock_spin(&sched_lock);
MPASS(sq != NULL);
/* Thread is asleep on sleep queue sq, so wake it up. */
sleepq_remove_thread(sq, td);
sleepq_release(wchan);
sleepq_resume_thread(td, -1);
}
/*
* Abort a thread as if an interrupt had occurred. Only abort
* interruptible waits (unfortunately it isn't safe to abort others).
*
* XXX: What in the world does the comment below mean?
* Also, whatever the signal code does...
*/
void
sleepq_abort(struct thread *td)
{
void *wchan;
mtx_assert(&sched_lock, MA_OWNED);
MPASS(TD_ON_SLEEPQ(td));
MPASS(td->td_flags & TDF_SINTR);
/*
* If the TDF_TIMEOUT flag is set, just leave. A
* timeout is scheduled anyhow.
*/
if (td->td_flags & TDF_TIMEOUT)
return;
CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_proc->p_comm);
wchan = td->td_wchan;
mtx_unlock_spin(&sched_lock);
sleepq_remove(td, wchan);
mtx_lock_spin(&sched_lock);
}