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mirror of https://git.FreeBSD.org/src.git synced 2024-12-30 12:04:07 +00:00
freebsd/sys/kern/kern_condvar.c
2001-12-10 05:51:45 +00:00

579 lines
14 KiB
C

/*-
* Copyright (c) 2000 Jake Burkholder <jake@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.
*
* 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.
*
* $FreeBSD$
*/
#include "opt_ktrace.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/condvar.h>
#include <sys/signalvar.h>
#include <sys/resourcevar.h>
#ifdef KTRACE
#include <sys/uio.h>
#include <sys/ktrace.h>
#endif
/*
* Common sanity checks for cv_wait* functions.
*/
#define CV_ASSERT(cvp, mp, td) do { \
KASSERT((td) != NULL, ("%s: curthread NULL", __func__)); \
KASSERT((td)->td_proc->p_stat == SRUN, ("%s: not SRUN", __func__)); \
KASSERT((cvp) != NULL, ("%s: cvp NULL", __func__)); \
KASSERT((mp) != NULL, ("%s: mp NULL", __func__)); \
mtx_assert((mp), MA_OWNED | MA_NOTRECURSED); \
} while (0)
#ifdef CV_DEBUG
#define CV_WAIT_VALIDATE(cvp, mp) do { \
if (TAILQ_EMPTY(&(cvp)->cv_waitq)) { \
/* Only waiter. */ \
(cvp)->cv_mtx = (mp); \
} else { \
/* \
* Other waiter; assert that we're using the \
* same mutex. \
*/ \
KASSERT((cvp)->cv_mtx == (mp), \
("%s: Multiple mutexes", __func__)); \
} \
} while (0)
#define CV_SIGNAL_VALIDATE(cvp) do { \
if (!TAILQ_EMPTY(&(cvp)->cv_waitq)) { \
KASSERT(mtx_owned((cvp)->cv_mtx), \
("%s: Mutex not owned", __func__)); \
} \
} while (0)
#else
#define CV_WAIT_VALIDATE(cvp, mp)
#define CV_SIGNAL_VALIDATE(cvp)
#endif
static void cv_timedwait_end(void *arg);
/*
* Initialize a condition variable. Must be called before use.
*/
void
cv_init(struct cv *cvp, const char *desc)
{
TAILQ_INIT(&cvp->cv_waitq);
cvp->cv_mtx = NULL;
cvp->cv_description = desc;
}
/*
* Destroy a condition variable. The condition variable must be re-initialized
* in order to be re-used.
*/
void
cv_destroy(struct cv *cvp)
{
KASSERT(cv_waitq_empty(cvp), ("%s: cv_waitq non-empty", __func__));
}
/*
* Common code for cv_wait* functions. All require sched_lock.
*/
/*
* Switch context.
*/
static __inline void
cv_switch(struct thread *td)
{
td->td_proc->p_stat = SSLEEP;
td->td_proc->p_stats->p_ru.ru_nvcsw++;
mi_switch();
CTR3(KTR_PROC, "cv_switch: resume thread %p (pid %d, %s)", td,
td->td_proc->p_pid, td->td_proc->p_comm);
}
/*
* Switch context, catching signals.
*/
static __inline int
cv_switch_catch(struct thread *td)
{
struct proc *p;
int sig;
/*
* We put ourselves on the sleep queue and start our timeout before
* calling CURSIG, as we could stop there, and a wakeup or a SIGCONT (or
* both) could occur while we were stopped. A SIGCONT would cause us to
* be marked as SSLEEP without resuming us, thus we must be ready for
* sleep when CURSIG is called. If the wakeup happens while we're
* stopped, td->td_wchan will be 0 upon return from CURSIG.
*/
td->td_flags |= TDF_SINTR;
mtx_unlock_spin(&sched_lock);
p = td->td_proc;
PROC_LOCK(p);
sig = CURSIG(p); /* XXXKSE */
mtx_lock_spin(&sched_lock);
PROC_UNLOCK_NOSWITCH(p);
if (sig != 0) {
if (td->td_wchan != NULL)
cv_waitq_remove(td);
td->td_proc->p_stat = SRUN;
} else if (td->td_wchan != NULL) {
cv_switch(td);
}
td->td_flags &= ~TDF_SINTR;
return sig;
}
/*
* Add a thread to the wait queue of a condition variable.
*/
static __inline void
cv_waitq_add(struct cv *cvp, struct thread *td)
{
/*
* Process may be sitting on a slpque if asleep() was called, remove it
* before re-adding.
*/
if (td->td_wchan != NULL)
unsleep(td);
td->td_flags |= TDF_CVWAITQ;
td->td_wchan = cvp;
td->td_wmesg = cvp->cv_description;
td->td_kse->ke_slptime = 0; /* XXXKSE */
td->td_ksegrp->kg_slptime = 0; /* XXXKSE */
td->td_ksegrp->kg_pri.pri_native = td->td_ksegrp->kg_pri.pri_level;
CTR3(KTR_PROC, "cv_waitq_add: thread %p (pid %d, %s)", td,
td->td_proc->p_pid, td->td_proc->p_comm);
TAILQ_INSERT_TAIL(&cvp->cv_waitq, td, td_slpq);
}
/*
* Wait on a condition variable. The current thread is placed on the condition
* variable's wait queue and suspended. A cv_signal or cv_broadcast on the same
* condition variable will resume the thread. The mutex is released before
* sleeping and will be held on return. It is recommended that the mutex be
* held when cv_signal or cv_broadcast are called.
*/
void
cv_wait(struct cv *cvp, struct mtx *mp)
{
struct thread *td;
WITNESS_SAVE_DECL(mp);
td = curthread;
#ifdef KTRACE
if (td->td_proc && KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_SLEEP(0, &mp->mtx_object);
WITNESS_SAVE(&mp->mtx_object, mp);
mtx_lock_spin(&sched_lock);
if (cold || panicstr) {
/*
* After a panic, or during autoconfiguration, just give
* interrupts a chance, then just return; don't run any other
* thread or panic below, in case this is the idle process and
* already asleep.
*/
mtx_unlock_spin(&sched_lock);
return;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_unlock_flags(mp, MTX_NOSWITCH);
cv_waitq_add(cvp, td);
cv_switch(td);
mtx_unlock_spin(&sched_lock);
#ifdef KTRACE
if (KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 0, 0);
#endif
PICKUP_GIANT();
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
}
/*
* Wait on a condition variable, allowing interruption by signals. Return 0 if
* the thread was resumed with cv_signal or cv_broadcast, EINTR or ERESTART if
* a signal was caught. If ERESTART is returned the system call should be
* restarted if possible.
*/
int
cv_wait_sig(struct cv *cvp, struct mtx *mp)
{
struct thread *td;
struct proc *p;
int rval;
int sig;
WITNESS_SAVE_DECL(mp);
td = curthread;
p = td->td_proc;
rval = 0;
#ifdef KTRACE
if (td->td_proc && KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_SLEEP(0, &mp->mtx_object);
WITNESS_SAVE(&mp->mtx_object, mp);
mtx_lock_spin(&sched_lock);
if (cold || panicstr) {
/*
* After a panic, or during autoconfiguration, just give
* interrupts a chance, then just return; don't run any other
* procs or panic below, in case this is the idle process and
* already asleep.
*/
mtx_unlock_spin(&sched_lock);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_unlock_flags(mp, MTX_NOSWITCH);
cv_waitq_add(cvp, td);
sig = cv_switch_catch(td);
mtx_unlock_spin(&sched_lock);
PICKUP_GIANT();
PROC_LOCK(p);
if (sig == 0)
sig = CURSIG(p); /* XXXKSE */
if (sig != 0) {
if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
rval = EINTR;
else
rval = ERESTART;
}
PROC_UNLOCK(p);
#ifdef KTRACE
mtx_lock(&Giant);
if (KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 0, 0);
mtx_unlock(&Giant);
#endif
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
return (rval);
}
/*
* Wait on a condition variable for at most timo/hz seconds. Returns 0 if the
* process was resumed by cv_signal or cv_broadcast, EWOULDBLOCK if the timeout
* expires.
*/
int
cv_timedwait(struct cv *cvp, struct mtx *mp, int timo)
{
struct thread *td;
int rval;
WITNESS_SAVE_DECL(mp);
td = curthread;
rval = 0;
#ifdef KTRACE
ktrcsw(td->td_proc->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_SLEEP(0, &mp->mtx_object);
WITNESS_SAVE(&mp->mtx_object, mp);
mtx_lock_spin(&sched_lock);
if (cold || panicstr) {
/*
* After a panic, or during autoconfiguration, just give
* interrupts a chance, then just return; don't run any other
* thread or panic below, in case this is the idle process and
* already asleep.
*/
mtx_unlock_spin(&sched_lock);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_unlock_flags(mp, MTX_NOSWITCH);
cv_waitq_add(cvp, td);
callout_reset(&td->td_slpcallout, timo, cv_timedwait_end, td);
cv_switch(td);
if (td->td_flags & TDF_TIMEOUT) {
td->td_flags &= ~TDF_TIMEOUT;
rval = EWOULDBLOCK;
} else if (td->td_flags & TDF_TIMOFAIL)
td->td_flags &= ~TDF_TIMOFAIL;
else if (callout_stop(&td->td_slpcallout) == 0) {
/*
* Work around race with cv_timedwait_end similar to that
* between msleep and endtsleep.
*/
td->td_flags |= TDF_TIMEOUT;
td->td_proc->p_stats->p_ru.ru_nivcsw++;
mi_switch();
}
mtx_unlock_spin(&sched_lock);
#ifdef KTRACE
if (KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 0, 0);
#endif
PICKUP_GIANT();
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
return (rval);
}
/*
* Wait on a condition variable for at most timo/hz seconds, allowing
* interruption by signals. Returns 0 if the thread was resumed by cv_signal
* or cv_broadcast, EWOULDBLOCK if the timeout expires, and EINTR or ERESTART if
* a signal was caught.
*/
int
cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo)
{
struct thread *td;
struct proc *p;
int rval;
int sig;
WITNESS_SAVE_DECL(mp);
td = curthread;
p = td->td_proc;
rval = 0;
#ifdef KTRACE
if (td->td_proc && KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_SLEEP(0, &mp->mtx_object);
WITNESS_SAVE(&mp->mtx_object, mp);
mtx_lock_spin(&sched_lock);
if (cold || panicstr) {
/*
* After a panic, or during autoconfiguration, just give
* interrupts a chance, then just return; don't run any other
* thread or panic below, in case this is the idle process and
* already asleep.
*/
mtx_unlock_spin(&sched_lock);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_unlock_flags(mp, MTX_NOSWITCH);
cv_waitq_add(cvp, td);
callout_reset(&td->td_slpcallout, timo, cv_timedwait_end, td);
sig = cv_switch_catch(td);
if (td->td_flags & TDF_TIMEOUT) {
td->td_flags &= ~TDF_TIMEOUT;
rval = EWOULDBLOCK;
} else if (td->td_flags & TDF_TIMOFAIL)
td->td_flags &= ~TDF_TIMOFAIL;
else if (callout_stop(&td->td_slpcallout) == 0) {
/*
* Work around race with cv_timedwait_end similar to that
* between msleep and endtsleep.
*/
td->td_flags |= TDF_TIMEOUT;
td->td_proc->p_stats->p_ru.ru_nivcsw++;
mi_switch();
}
mtx_unlock_spin(&sched_lock);
PICKUP_GIANT();
PROC_LOCK(p);
if (sig == 0)
sig = CURSIG(p);
if (sig != 0) {
if (SIGISMEMBER(p->p_sigacts->ps_sigintr, sig))
rval = EINTR;
else
rval = ERESTART;
}
PROC_UNLOCK(p);
#ifdef KTRACE
mtx_lock(&Giant);
if (KTRPOINT(td->td_proc, KTR_CSW))
ktrcsw(td->td_proc->p_tracep, 0, 0);
mtx_unlock(&Giant);
#endif
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
return (rval);
}
/*
* Common code for signal and broadcast. Assumes waitq is not empty. Must be
* called with sched_lock held.
*/
static __inline void
cv_wakeup(struct cv *cvp)
{
struct thread *td;
mtx_assert(&sched_lock, MA_OWNED);
td = TAILQ_FIRST(&cvp->cv_waitq);
KASSERT(td->td_wchan == cvp, ("%s: bogus wchan", __func__));
KASSERT(td->td_flags & TDF_CVWAITQ, ("%s: not on waitq", __func__));
TAILQ_REMOVE(&cvp->cv_waitq, td, td_slpq);
td->td_flags &= ~TDF_CVWAITQ;
td->td_wchan = 0;
if (td->td_proc->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(td); */
CTR3(KTR_PROC, "cv_signal: thread %p (pid %d, %s)",
td, td->td_proc->p_pid, td->td_proc->p_comm);
if (td->td_ksegrp->kg_slptime > 1) /* XXXKSE */
updatepri(td);
td->td_kse->ke_slptime = 0;
td->td_ksegrp->kg_slptime = 0;
td->td_proc->p_stat = SRUN;
if (td->td_proc->p_sflag & PS_INMEM) {
setrunqueue(td);
maybe_resched(td->td_ksegrp);
} else {
td->td_proc->p_sflag |= PS_SWAPINREQ;
wakeup(&proc0); /* XXXKSE */
}
/* END INLINE EXPANSION */
}
}
/*
* Signal a condition variable, wakes up one waiting thread. Will also wakeup
* the swapper if the process is not in memory, so that it can bring the
* sleeping process in. Note that this may also result in additional threads
* being made runnable. Should be called with the same mutex as was passed to
* cv_wait held.
*/
void
cv_signal(struct cv *cvp)
{
KASSERT(cvp != NULL, ("%s: cvp NULL", __func__));
mtx_lock_spin(&sched_lock);
if (!TAILQ_EMPTY(&cvp->cv_waitq)) {
CV_SIGNAL_VALIDATE(cvp);
cv_wakeup(cvp);
}
mtx_unlock_spin(&sched_lock);
}
/*
* Broadcast a signal to a condition variable. Wakes up all waiting threads.
* Should be called with the same mutex as was passed to cv_wait held.
*/
void
cv_broadcast(struct cv *cvp)
{
KASSERT(cvp != NULL, ("%s: cvp NULL", __func__));
mtx_lock_spin(&sched_lock);
CV_SIGNAL_VALIDATE(cvp);
while (!TAILQ_EMPTY(&cvp->cv_waitq))
cv_wakeup(cvp);
mtx_unlock_spin(&sched_lock);
}
/*
* Remove a thread from the wait queue of its condition variable. This may be
* called externally.
*/
void
cv_waitq_remove(struct thread *td)
{
struct cv *cvp;
mtx_lock_spin(&sched_lock);
if ((cvp = td->td_wchan) != NULL && td->td_flags & TDF_CVWAITQ) {
TAILQ_REMOVE(&cvp->cv_waitq, td, td_slpq);
td->td_flags &= ~TDF_CVWAITQ;
td->td_wchan = NULL;
}
mtx_unlock_spin(&sched_lock);
}
/*
* Timeout function for cv_timedwait. Put the thread on the runqueue and set
* its timeout flag.
*/
static void
cv_timedwait_end(void *arg)
{
struct thread *td;
td = arg;
CTR3(KTR_PROC, "cv_timedwait_end: thread %p (pid %d, %s)", td, td->td_proc->p_pid,
td->td_proc->p_comm);
mtx_lock_spin(&sched_lock);
if (td->td_flags & TDF_TIMEOUT) {
td->td_flags &= ~TDF_TIMEOUT;
setrunqueue(td);
} else if (td->td_wchan != NULL) {
if (td->td_proc->p_stat == SSLEEP) /* XXXKSE */
setrunnable(td);
else
cv_waitq_remove(td);
td->td_flags |= TDF_TIMEOUT;
} else
td->td_flags |= TDF_TIMOFAIL;
mtx_unlock_spin(&sched_lock);
}