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/*-
* 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 <sys/cdefs.h>
__FBSDID("$FreeBSD: release/9.1.0/sys/kern/subr_sleepqueue.c 236344 2012-05-30 23:22:52Z rstone $");
#include "opt_sleepqueue_profiling.h"
#include "opt_ddb.h"
#include "opt_kdtrace.h"
#include "opt_sched.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/sched.h>
#include <sys/sdt.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>
#include <sys/sysctl.h>
#include <vm/uma.h>
#ifdef DDB
#include <ddb/ddb.h>
#endif
/*
* 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)]
#define NR_SLEEPQS 2
/*
* 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[NR_SLEEPQS]; /* (c) Blocked threads. */
u_int sq_blockedcnt[NR_SLEEPQS]; /* (c) N. of 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 lock_object *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");
static void sleepq_profile(const char *wmesg);
static int prof_enabled;
#endif
static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
static uma_zone_t sleepq_zone;
/*
* Prototypes for non-exported routines.
*/
static int sleepq_catch_signals(void *wchan, int pri);
static int sleepq_check_signals(void);
static int sleepq_check_timeout(void);
#ifdef INVARIANTS
static void sleepq_dtor(void *mem, int size, void *arg);
#endif
static int sleepq_init(void *mem, int size, int flags);
static int sleepq_resume_thread(struct sleepqueue *sq, struct thread *td,
int pri);
static void sleepq_switch(void *wchan, int pri);
static void sleepq_timeout(void *arg);
SDT_PROBE_DECLARE(sched, , , sleep);
SDT_PROBE_DECLARE(sched, , , wakeup);
/*
* 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 | MTX_RECURSE);
#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
}
sleepq_zone = uma_zcreate("SLEEPQUEUE", sizeof(struct sleepqueue),
#ifdef INVARIANTS
NULL, sleepq_dtor, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
#else
NULL, NULL, sleepq_init, NULL, UMA_ALIGN_CACHE, 0);
#endif
thread0.td_sleepqueue = sleepq_alloc();
}
/*
* Get a sleep queue for a new thread.
*/
struct sleepqueue *
sleepq_alloc(void)
{
return (uma_zalloc(sleepq_zone, M_WAITOK));
}
/*
* Free a sleep queue when a thread is destroyed.
*/
void
sleepq_free(struct sleepqueue *sq)
{
uma_zfree(sleepq_zone, sq);
}
/*
* Lock the sleep queue chain associated with the specified wait channel.
*/
void
sleepq_lock(void *wchan)
{
struct sleepqueue_chain *sc;
sc = SC_LOOKUP(wchan);
mtx_lock_spin(&sc->sc_lock);
}
/*
* Look up the sleep queue associated with a given wait channel in the hash
* table locking the associated sleep queue chain. 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_assert(&sc->sc_lock, MA_OWNED);
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 sleep queue 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(void *wchan, struct lock_object *lock, const char *wmesg, int flags,
int queue)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
struct thread *td;
td = curthread;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
MPASS(td->td_sleepqueue != NULL);
MPASS(wchan != NULL);
MPASS((queue >= 0) && (queue < NR_SLEEPQS));
/* If this thread is not allowed to sleep, die a horrible death. */
KASSERT(!(td->td_pflags & TDP_NOSLEEPING),
("Trying sleep, but thread marked as sleeping prohibited"));
/* Look up the sleep queue associated with the wait channel 'wchan'. */
sq = sleepq_lookup(wchan);
/*
* If the wait channel does not already have a sleep queue, use
* this thread's sleep queue. Otherwise, insert the current thread
* into the sleep queue already in use by this wait channel.
*/
if (sq == NULL) {
#ifdef INVARIANTS
int i;
sq = td->td_sleepqueue;
for (i = 0; i < NR_SLEEPQS; i++) {
KASSERT(TAILQ_EMPTY(&sq->sq_blocked[i]),
("thread's sleep queue %d is not empty", i));
KASSERT(sq->sq_blockedcnt[i] == 0,
("thread's sleep queue %d count mismatches", i));
}
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_lock = lock;
#endif
#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);
sq->sq_wchan = wchan;
sq->sq_type = flags & SLEEPQ_TYPE;
} else {
MPASS(wchan == sq->sq_wchan);
MPASS(lock == sq->sq_lock);
MPASS((flags & SLEEPQ_TYPE) == sq->sq_type);
LIST_INSERT_HEAD(&sq->sq_free, td->td_sleepqueue, sq_hash);
}
thread_lock(td);
TAILQ_INSERT_TAIL(&sq->sq_blocked[queue], td, td_slpq);
sq->sq_blockedcnt[queue]++;
td->td_sleepqueue = NULL;
td->td_sqqueue = queue;
td->td_wchan = wchan;
td->td_wmesg = wmesg;
if (flags & SLEEPQ_INTERRUPTIBLE) {
td->td_flags |= TDF_SINTR;
td->td_flags &= ~TDF_SLEEPABORT;
if (flags & SLEEPQ_STOP_ON_BDRY)
td->td_flags |= TDF_SBDRY;
}
thread_unlock(td);
}
/*
* 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_curcpu(&td->td_slpcallout, timo, sleepq_timeout, td);
}
/*
* Return the number of actual sleepers for the specified queue.
*/
u_int
sleepq_sleepcnt(void *wchan, int queue)
{
struct sleepqueue *sq;
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
MPASS((queue >= 0) && (queue < NR_SLEEPQS));
sq = sleepq_lookup(wchan);
if (sq == NULL)
return (0);
return (sq->sq_blockedcnt[queue]);
}
/*
* Marks the pending sleep of the current thread as interruptible and
* makes an initial check for pending signals before putting a thread
* to sleep. Enters and exits with the thread lock held. Thread lock
* may have transitioned from the sleepq lock to a run lock.
*/
static int
sleepq_catch_signals(void *wchan, int pri)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
struct thread *td;
struct proc *p;
struct sigacts *ps;
int sig, ret, stop_allowed;
td = curthread;
p = curproc;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
MPASS(wchan != NULL);
if ((td->td_pflags & TDP_WAKEUP) != 0) {
td->td_pflags &= ~TDP_WAKEUP;
ret = EINTR;
thread_lock(td);
goto out;
}
/*
* See if there are any pending signals for this thread. If not
* we can switch immediately. Otherwise do the signal processing
* directly.
*/
thread_lock(td);
if ((td->td_flags & (TDF_NEEDSIGCHK | TDF_NEEDSUSPCHK)) == 0) {
sleepq_switch(wchan, pri);
return (0);
}
stop_allowed = (td->td_flags & TDF_SBDRY) ? SIG_STOP_NOT_ALLOWED :
SIG_STOP_ALLOWED;
thread_unlock(td);
mtx_unlock_spin(&sc->sc_lock);
CTR3(KTR_PROC, "sleepq catching signals: thread %p (pid %ld, %s)",
(void *)td, (long)p->p_pid, td->td_name);
PROC_LOCK(p);
ps = p->p_sigacts;
mtx_lock(&ps->ps_mtx);
sig = cursig(td, stop_allowed);
if (sig == 0) {
mtx_unlock(&ps->ps_mtx);
ret = thread_suspend_check(1);
MPASS(ret == 0 || ret == EINTR || ret == ERESTART);
} else {
if (SIGISMEMBER(ps->ps_sigintr, sig))
ret = EINTR;
else
ret = ERESTART;
mtx_unlock(&ps->ps_mtx);
}
/*
* Lock the per-process spinlock prior to dropping the PROC_LOCK
* to avoid a signal delivery race. PROC_LOCK, PROC_SLOCK, and
* thread_lock() are currently held in tdsendsignal().
*/
PROC_SLOCK(p);
mtx_lock_spin(&sc->sc_lock);
PROC_UNLOCK(p);
thread_lock(td);
PROC_SUNLOCK(p);
if (ret == 0) {
sleepq_switch(wchan, pri);
return (0);
}
out:
/*
* There were pending signals and this thread is still
* on the sleep queue, remove it from the sleep queue.
*/
if (TD_ON_SLEEPQ(td)) {
sq = sleepq_lookup(wchan);
if (sleepq_resume_thread(sq, td, 0)) {
#ifdef INVARIANTS
/*
* This thread hasn't gone to sleep yet, so it
* should not be swapped out.
*/
panic("not waking up swapper");
#endif
}
}
mtx_unlock_spin(&sc->sc_lock);
MPASS(td->td_lock != &sc->sc_lock);
return (ret);
}
/*
* Switches to another thread if we are still asleep on a sleep queue.
* Returns with thread lock.
*/
static void
sleepq_switch(void *wchan, int pri)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
struct thread *td;
td = curthread;
sc = SC_LOOKUP(wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* If we have a sleep queue, then we've already been woken up, so
* just return.
*/
if (td->td_sleepqueue != NULL) {
mtx_unlock_spin(&sc->sc_lock);
return;
}
/*
* If TDF_TIMEOUT is set, then our sleep has been timed out
* already but we are still on the sleep queue, so dequeue the
* thread and return.
*/
if (td->td_flags & TDF_TIMEOUT) {
MPASS(TD_ON_SLEEPQ(td));
sq = sleepq_lookup(wchan);
if (sleepq_resume_thread(sq, td, 0)) {
#ifdef INVARIANTS
/*
* This thread hasn't gone to sleep yet, so it
* should not be swapped out.
*/
panic("not waking up swapper");
#endif
}
mtx_unlock_spin(&sc->sc_lock);
return;
}
#ifdef SLEEPQUEUE_PROFILING
if (prof_enabled)
sleepq_profile(td->td_wmesg);
#endif
MPASS(td->td_sleepqueue == NULL);
sched_sleep(td, pri);
thread_lock_set(td, &sc->sc_lock);
SDT_PROBE0(sched, , , sleep);
TD_SET_SLEEPING(td);
mi_switch(SW_VOL | SWT_SLEEPQ, 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_name);
}
/*
* Check to see if we timed out.
*/
static int
sleepq_check_timeout(void)
{
struct thread *td;
td = curthread;
THREAD_LOCK_ASSERT(td, MA_OWNED);
/*
* 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 | SWT_SLEEPQTIMO, NULL);
}
return (0);
}
/*
* Check to see if we were awoken by a signal.
*/
static int
sleepq_check_signals(void)
{
struct thread *td;
td = curthread;
THREAD_LOCK_ASSERT(td, MA_OWNED);
/* We are no longer in an interruptible sleep. */
if (td->td_flags & TDF_SINTR)
td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
if (td->td_flags & TDF_SLEEPABORT) {
td->td_flags &= ~TDF_SLEEPABORT;
return (td->td_intrval);
}
return (0);
}
/*
* Block the current thread until it is awakened from its sleep queue.
*/
void
sleepq_wait(void *wchan, int pri)
{
struct thread *td;
td = curthread;
MPASS(!(td->td_flags & TDF_SINTR));
thread_lock(td);
sleepq_switch(wchan, pri);
thread_unlock(td);
}
/*
* 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 pri)
{
int rcatch;
int rval;
rcatch = sleepq_catch_signals(wchan, pri);
rval = sleepq_check_signals();
thread_unlock(curthread);
if (rcatch)
return (rcatch);
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 pri)
{
struct thread *td;
int rval;
td = curthread;
MPASS(!(td->td_flags & TDF_SINTR));
thread_lock(td);
sleepq_switch(wchan, pri);
rval = sleepq_check_timeout();
thread_unlock(td);
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 pri)
{
int rcatch, rvalt, rvals;
rcatch = sleepq_catch_signals(wchan, pri);
rvalt = sleepq_check_timeout();
rvals = sleepq_check_signals();
thread_unlock(curthread);
if (rcatch)
return (rcatch);
if (rvals)
return (rvals);
return (rvalt);
}
/*
* Returns the type of sleepqueue given a waitchannel.
*/
int
sleepq_type(void *wchan)
{
struct sleepqueue *sq;
int type;
MPASS(wchan != NULL);
sleepq_lock(wchan);
sq = sleepq_lookup(wchan);
if (sq == NULL) {
sleepq_release(wchan);
return (-1);
}
type = sq->sq_type;
sleepq_release(wchan);
return (type);
}
/*
* Removes a thread from a sleep queue and makes it
* runnable.
*/
static int
sleepq_resume_thread(struct sleepqueue *sq, struct thread *td, int pri)
{
struct sleepqueue_chain *sc;
MPASS(td != NULL);
MPASS(sq->sq_wchan != NULL);
MPASS(td->td_wchan == sq->sq_wchan);
MPASS(td->td_sqqueue < NR_SLEEPQS && td->td_sqqueue >= 0);
THREAD_LOCK_ASSERT(td, MA_OWNED);
sc = SC_LOOKUP(sq->sq_wchan);
mtx_assert(&sc->sc_lock, MA_OWNED);
SDT_PROBE2(sched, , , wakeup, td, td->td_proc);
/* Remove the thread from the queue. */
sq->sq_blockedcnt[td->td_sqqueue]--;
TAILQ_REMOVE(&sq->sq_blocked[td->td_sqqueue], 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);
td->td_wmesg = NULL;
td->td_wchan = NULL;
td->td_flags &= ~(TDF_SINTR | TDF_SBDRY);
CTR3(KTR_PROC, "sleepq_wakeup: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, td->td_name);
/* Adjust priority if requested. */
MPASS(pri == 0 || (pri >= PRI_MIN && pri <= PRI_MAX));
if (pri != 0 && td->td_priority > pri &&
PRI_BASE(td->td_pri_class) == PRI_TIMESHARE)
sched_prio(td, 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. There's no need to mark the
* thread runnable in that case.
*/
if (TD_IS_SLEEPING(td)) {
TD_CLR_SLEEPING(td);
return (setrunnable(td));
}
return (0);
}
#ifdef INVARIANTS
/*
* UMA zone item deallocator.
*/
static void
sleepq_dtor(void *mem, int size, void *arg)
{
struct sleepqueue *sq;
int i;
sq = mem;
for (i = 0; i < NR_SLEEPQS; i++) {
MPASS(TAILQ_EMPTY(&sq->sq_blocked[i]));
MPASS(sq->sq_blockedcnt[i] == 0);
}
}
#endif
/*
* UMA zone item initializer.
*/
static int
sleepq_init(void *mem, int size, int flags)
{
struct sleepqueue *sq;
int i;
bzero(mem, size);
sq = mem;
for (i = 0; i < NR_SLEEPQS; i++) {
TAILQ_INIT(&sq->sq_blocked[i]);
sq->sq_blockedcnt[i] = 0;
}
LIST_INIT(&sq->sq_free);
return (0);
}
/*
* Find the highest priority thread sleeping on a wait channel and resume it.
*/
int
sleepq_signal(void *wchan, int flags, int pri, int queue)
{
struct sleepqueue *sq;
struct thread *td, *besttd;
int wakeup_swapper;
CTR2(KTR_PROC, "sleepq_signal(%p, %d)", wchan, flags);
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
MPASS((queue >= 0) && (queue < NR_SLEEPQS));
sq = sleepq_lookup(wchan);
if (sq == NULL)
return (0);
KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
("%s: mismatch between sleep/wakeup and cv_*", __func__));
/*
* Find the highest priority thread on the queue. If there is a
* tie, use the thread that first appears in the queue as it has
* been sleeping the longest since threads are always added to
* the tail of sleep queues.
*/
besttd = NULL;
TAILQ_FOREACH(td, &sq->sq_blocked[queue], td_slpq) {
if (besttd == NULL || td->td_priority < besttd->td_priority)
besttd = td;
}
MPASS(besttd != NULL);
thread_lock(besttd);
wakeup_swapper = sleepq_resume_thread(sq, besttd, pri);
thread_unlock(besttd);
return (wakeup_swapper);
}
/*
* Resume all threads sleeping on a specified wait channel.
*/
int
sleepq_broadcast(void *wchan, int flags, int pri, int queue)
{
struct sleepqueue *sq;
struct thread *td, *tdn;
int wakeup_swapper;
CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
KASSERT(wchan != NULL, ("%s: invalid NULL wait channel", __func__));
MPASS((queue >= 0) && (queue < NR_SLEEPQS));
sq = sleepq_lookup(wchan);
if (sq == NULL)
return (0);
KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
("%s: mismatch between sleep/wakeup and cv_*", __func__));
/* Resume all blocked threads on the sleep queue. */
wakeup_swapper = 0;
TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) {
thread_lock(td);
if (sleepq_resume_thread(sq, td, pri))
wakeup_swapper = 1;
thread_unlock(td);
}
return (wakeup_swapper);
}
/*
* 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_chain *sc;
struct sleepqueue *sq;
struct thread *td;
void *wchan;
int wakeup_swapper;
td = arg;
wakeup_swapper = 0;
CTR3(KTR_PROC, "sleepq_timeout: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
/*
* First, see if the thread is asleep and get the wait channel if
* it is.
*/
thread_lock(td);
if (TD_IS_SLEEPING(td) && TD_ON_SLEEPQ(td)) {
wchan = td->td_wchan;
sc = SC_LOOKUP(wchan);
THREAD_LOCKPTR_ASSERT(td, &sc->sc_lock);
sq = sleepq_lookup(wchan);
MPASS(sq != NULL);
td->td_flags |= TDF_TIMEOUT;
wakeup_swapper = sleepq_resume_thread(sq, td, 0);
thread_unlock(td);
if (wakeup_swapper)
kick_proc0();
return;
}
/*
* If the thread is on the SLEEPQ but isn't sleeping yet, it
* can either be on another CPU in between sleepq_add() and
* one of the sleepq_*wait*() routines or it can be in
* sleepq_catch_signals().
*/
if (TD_ON_SLEEPQ(td)) {
td->td_flags |= TDF_TIMEOUT;
thread_unlock(td);
return;
}
/*
* 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);
wakeup_swapper = setrunnable(td);
} else
td->td_flags |= TDF_TIMOFAIL;
thread_unlock(td);
if (wakeup_swapper)
kick_proc0();
}
/*
* 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;
int wakeup_swapper;
/*
* 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);
sleepq_lock(wchan);
sq = sleepq_lookup(wchan);
/*
* We can not lock the thread here as it may be sleeping on a
* different sleepq. However, holding the sleepq lock for this
* wchan can guarantee that we do not miss a wakeup for this
* channel. The asserts below will catch any false positives.
*/
if (!TD_ON_SLEEPQ(td) || td->td_wchan != wchan) {
sleepq_release(wchan);
return;
}
/* Thread is asleep on sleep queue sq, so wake it up. */
thread_lock(td);
MPASS(sq != NULL);
MPASS(td->td_wchan == wchan);
wakeup_swapper = sleepq_resume_thread(sq, td, 0);
thread_unlock(td);
sleepq_release(wchan);
if (wakeup_swapper)
kick_proc0();
}
/*
* Abort a thread as if an interrupt had occurred. Only abort
* interruptible waits (unfortunately it isn't safe to abort others).
*/
int
sleepq_abort(struct thread *td, int intrval)
{
struct sleepqueue *sq;
void *wchan;
THREAD_LOCK_ASSERT(td, MA_OWNED);
MPASS(TD_ON_SLEEPQ(td));
MPASS(td->td_flags & TDF_SINTR);
MPASS(intrval == EINTR || intrval == ERESTART);
/*
* If the TDF_TIMEOUT flag is set, just leave. A
* timeout is scheduled anyhow.
*/
if (td->td_flags & TDF_TIMEOUT)
return (0);
CTR3(KTR_PROC, "sleepq_abort: thread %p (pid %ld, %s)",
(void *)td, (long)td->td_proc->p_pid, (void *)td->td_name);
td->td_intrval = intrval;
td->td_flags |= TDF_SLEEPABORT;
/*
* If the thread has not slept yet it will find the signal in
* sleepq_catch_signals() and call sleepq_resume_thread. Otherwise
* we have to do it here.
*/
if (!TD_IS_SLEEPING(td))
return (0);
wchan = td->td_wchan;
MPASS(wchan != NULL);
sq = sleepq_lookup(wchan);
MPASS(sq != NULL);
/* Thread is asleep on sleep queue sq, so wake it up. */
return (sleepq_resume_thread(sq, td, 0));
}
#ifdef SLEEPQUEUE_PROFILING
#define SLEEPQ_PROF_LOCATIONS 1024
#define SLEEPQ_SBUFSIZE 512
struct sleepq_prof {
LIST_ENTRY(sleepq_prof) sp_link;
const char *sp_wmesg;
long sp_count;
};
LIST_HEAD(sqphead, sleepq_prof);
struct sqphead sleepq_prof_free;
struct sqphead sleepq_hash[SC_TABLESIZE];
static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
static struct mtx sleepq_prof_lock;
MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
static void
sleepq_profile(const char *wmesg)
{
struct sleepq_prof *sp;
mtx_lock_spin(&sleepq_prof_lock);
if (prof_enabled == 0)
goto unlock;
LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
if (sp->sp_wmesg == wmesg)
goto done;
sp = LIST_FIRST(&sleepq_prof_free);
if (sp == NULL)
goto unlock;
sp->sp_wmesg = wmesg;
LIST_REMOVE(sp, sp_link);
LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
done:
sp->sp_count++;
unlock:
mtx_unlock_spin(&sleepq_prof_lock);
return;
}
static void
sleepq_prof_reset(void)
{
struct sleepq_prof *sp;
int enabled;
int i;
mtx_lock_spin(&sleepq_prof_lock);
enabled = prof_enabled;
prof_enabled = 0;
for (i = 0; i < SC_TABLESIZE; i++)
LIST_INIT(&sleepq_hash[i]);
LIST_INIT(&sleepq_prof_free);
for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
sp = &sleepq_profent[i];
sp->sp_wmesg = NULL;
sp->sp_count = 0;
LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
}
prof_enabled = enabled;
mtx_unlock_spin(&sleepq_prof_lock);
}
static int
enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
{
int error, v;
v = prof_enabled;
error = sysctl_handle_int(oidp, &v, v, req);
if (error)
return (error);
if (req->newptr == NULL)
return (error);
if (v == prof_enabled)
return (0);
if (v == 1)
sleepq_prof_reset();
mtx_lock_spin(&sleepq_prof_lock);
prof_enabled = !!v;
mtx_unlock_spin(&sleepq_prof_lock);
return (0);
}
static int
reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
{
int error, v;
v = 0;
error = sysctl_handle_int(oidp, &v, 0, req);
if (error)
return (error);
if (req->newptr == NULL)
return (error);
if (v == 0)
return (0);
sleepq_prof_reset();
return (0);
}
static int
dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
{
struct sleepq_prof *sp;
struct sbuf *sb;
int enabled;
int error;
int i;
error = sysctl_wire_old_buffer(req, 0);
if (error != 0)
return (error);
sb = sbuf_new_for_sysctl(NULL, NULL, SLEEPQ_SBUFSIZE, req);
sbuf_printf(sb, "\nwmesg\tcount\n");
enabled = prof_enabled;
mtx_lock_spin(&sleepq_prof_lock);
prof_enabled = 0;
mtx_unlock_spin(&sleepq_prof_lock);
for (i = 0; i < SC_TABLESIZE; i++) {
LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
sbuf_printf(sb, "%s\t%ld\n",
sp->sp_wmesg, sp->sp_count);
}
}
mtx_lock_spin(&sleepq_prof_lock);
prof_enabled = enabled;
mtx_unlock_spin(&sleepq_prof_lock);
error = sbuf_finish(sb);
sbuf_delete(sb);
return (error);
}
SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, reset_sleepq_prof_stats, "I",
"Reset sleepqueue profiling statistics");
SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
#endif
#ifdef DDB
DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
{
struct sleepqueue_chain *sc;
struct sleepqueue *sq;
#ifdef INVARIANTS
struct lock_object *lock;
#endif
struct thread *td;
void *wchan;
int i;
if (!have_addr)
return;
/*
* First, see if there is an active sleep queue for the wait channel
* indicated by the address.
*/
wchan = (void *)addr;
sc = SC_LOOKUP(wchan);
LIST_FOREACH(sq, &sc->sc_queues, sq_hash)
if (sq->sq_wchan == wchan)
goto found;
/*
* Second, see if there is an active sleep queue at the address
* indicated.
*/
for (i = 0; i < SC_TABLESIZE; i++)
LIST_FOREACH(sq, &sleepq_chains[i].sc_queues, sq_hash) {
if (sq == (struct sleepqueue *)addr)
goto found;
}
db_printf("Unable to locate a sleep queue via %p\n", (void *)addr);
return;
found:
db_printf("Wait channel: %p\n", sq->sq_wchan);
db_printf("Queue type: %d\n", sq->sq_type);
#ifdef INVARIANTS
if (sq->sq_lock) {
lock = sq->sq_lock;
db_printf("Associated Interlock: %p - (%s) %s\n", lock,
LOCK_CLASS(lock)->lc_name, lock->lo_name);
}
#endif
db_printf("Blocked threads:\n");
for (i = 0; i < NR_SLEEPQS; i++) {
db_printf("\nQueue[%d]:\n", i);
if (TAILQ_EMPTY(&sq->sq_blocked[i]))
db_printf("\tempty\n");
else
TAILQ_FOREACH(td, &sq->sq_blocked[0],
td_slpq) {
db_printf("\t%p (tid %d, pid %d, \"%s\")\n", td,
td->td_tid, td->td_proc->p_pid,
td->td_name);
}
db_printf("(expected: %u)\n", sq->sq_blockedcnt[i]);
}
}
/* Alias 'show sleepqueue' to 'show sleepq'. */
DB_SHOW_ALIAS(sleepqueue, db_show_sleepqueue);
#endif