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Implement condition variables.

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This commit is contained in:
Jason Evans 2001-01-16 01:00:43 +00:00
parent e01862e9b0
commit 238510fc46
9 changed files with 851 additions and 9 deletions
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13
share/man/man9/Makefile
View File

@ -13,7 +13,7 @@ MAN9= CONDSPLASSERT.9 DELAY.9 KASSERT.9 MD5.9 SPLASSERT.9 \
VOP_STRATEGY.9 \
accf_data.9 accf_http.9 at_exit.9 at_fork.9 atomic.9 \
bios.9 boot.9 buf.9 \
cd.9 copy.9 \
cd.9 condvar.9 copy.9 \
devfs_add_devswf.9 devfs_link.9 devfs_remove_dev.9 devstat.9 \
devtoname.9 \
fetch.9 \
@ -77,6 +77,17 @@ MLINKS+=atomic.9 atomic_subtract.9
MLINKS+=atomic.9 atomic_store.9
MLINKS+=at_exit.9 rm_at_exit.9
MLINKS+=at_fork.9 rm_at_fork.9
MLINKS+=condvar.9 cv_init.9
MLINKS+=condvar.9 cv_destroy.9
MLINKS+=condvar.9 cv_wait.9
MLINKS+=condvar.9 cv_wait_sig.9
MLINKS+=condvar.9 cv_timedwait.9
MLINKS+=condvar.9 cv_timedwait_sig.9
MLINKS+=condvar.9 cv_signal.9
MLINKS+=condvar.9 cv_broadcast.9
MLINKS+=condvar.9 cv_waitq_remove.9
MLINKS+=condvar.9 cv_waitq_empty.9
MLINKS+=condvar.9 cv_wmesg.9
MLINKS+=copy.9 copyin.9 copy.9 copyinstr.9 copy.9 copyout.9 copy.9 copystr.9
MLINKS+=devfs_link.9 devfs_makelink.9
MLINKS+=devstat.9 devicestat.9 devstat.9 devstat_add_entry.9

196
share/man/man9/condvar.9 Normal file
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@ -0,0 +1,196 @@
.\"
.\" Copyright (C) 2000 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.
.\"
.\" $FreeBSD$
.\"
.Dd December 11, 2000
.Dt CONDVAR 9
.Os
.Sh NAME
.Nm condvar ,
.Nm cv_init ,
.Nm cv_destroy ,
.Nm cv_wait ,
.Nm cv_wait_sig ,
.Nm cv_timedwait ,
.Nm cv_timedwait_sig ,
.Nm cv_signal ,
.Nm cv_broadcast ,
.Nm cv_waitq_remove ,
.Nm cv_waitq_empty ,
.Nm cv_wmesg
.Nd kernel condition variable
.Sh SYNOPSIS
.Fd #include <sys/condvar.h>
.Ft void
.Fn cv_init "struct cv *cvp" "const char *desc"
.Ft void
.Fn cv_destroy "struct cv *cvp"
.Ft void
.Fn cv_wait "struct cv *cvp" "struct mtx *mp"
.Ft int
.Fn cv_wait_sig "struct cv *cvp" "struct mtx *mp"
.Ft int
.Fn cv_timedwait "struct cv *cvp" "struct mtx *mp" "int timo"
.Ft int
.Fn cv_timedwait_sig "struct cv *cvp" "struct mtx *mp" "int timo"
.Ft void
.Fn cv_signal "struct cv *cvp"
.Ft void
.Fn cv_broadcast "struct cv *cvp"
.Ft void
.Fn cv_waitq_remove "struct proc *p"
.Ft int
.Fn cv_waitq_empty "struct cv *cvp"
.Ft const char *
.Fn cv_wmesg "struct cv *cvp"
.Sh DESCRIPTION
Condition variables are used in conjunction with mutexes to wait for conditions
to occur.
Condition variables are created with
.Fn cv_init ,
where
.Ar cvp
is a pointer to space for a
.Dv struct cv ,
and
.Ar desc
is a pointer to a null-terminated character string that describes the condition
variable.
Condition variables are destroyed with
.Fn cv_destroy .
Threads wait on condition variables by calling
.Fn cv_wait ,
.Fn cv_wait_sig ,
.Fn cv_timedwait ,
or
.Fn cv_timedwait_sig .
Threads unblock waiters by calling
.Fn cv_signal
to unblock one waiter, or
.Fn cv_broadcast
to unblock all waiters.
.Fn cv_waitq_remove
removes a waiting thread from a condition variable wait queue, if it is on one.
.Fn cv_waitq_empty
reports whether there are any waiters on
.Ar cvp .
.Fn cv_wmesg
returns the description string of
.Ar cvp ,
as set by the initial call to
.Fn cv_init .
.Pp
A thread must hold
.Ar mp
before calling
.Fn cv_wait ,
.Fn cv_wait_sig ,
.Fn cv_timedwait ,
or
.Fn cv_timedwait_sig .
When a thread waits on a condition,
.Ar mp
is atomically released before the thread is blocked, then atomically reacquired
before the function call returns.
All waiters must pass the same
.Ar mp
in conjunction with
.Ar cvp .
A thread must hold
.Ar mp
while calling
.Fn cv_signal
or
.Fn cv_broadcast ,
even though it isn't passed as an argument.
.Pp
When
.Fn cv_wait ,
.Fn cv_wait_sig ,
.Fn cv_timedwait ,
and
.Fn cv_timedwait_sig
unblock, their calling threads are made runnable.
.Fn cv_timedwait
and
.Fn cv_timedwait_sig
wait for at most
.Ar timo
/
.Dv HZ
seconds before being unblocked and returning
.Er EWOULDBLOCK ;
otherwise, they return 0.
.Fn cv_wait_sig
and
.Fn cv_timedwait_sig
return prematurely with a value of
.Er EINTR
or
.Er ERESTART
if a signal is caught, or 0 if signaled via
.Fn cv_signal
or
.Fn cv_broadcast .
.Sh RETURN VALUES
If successful,
.Fn cv_wait_sig ,
.Fn cv_timedwait ,
and
.Fn cv_timedwait_sig
return 0.
Otherwise, a non-zero error code is returned.
.Pp
.Fn cv_waitq_empty
returns non-zero if there are no threads on the wait queue; 0 otherwise.
.Pp
.Fn cv_wmesg
returns the description string that was passed to
.Fn cv_init .
.Sh ERRORS
.Fn cv_wait_sig
and
.Fn cv_timedwait_sig
will fail if:
.Bl -tag -width Er
.It Bq Er EINTR
An unmasked signal was caught.
.It Bq Er ERESTART
A masked signal was caught.
.El
.Pp
.Fn cv_timedwait
and
.Fn cv_timedwait_sig
will fail if:
.Bl -tag -width Er
.It Bq Er EWOULDBLOCK
Timeout expired.
.El
.Sh SEE ALSO
.Xr msleep 9 ,
.Xr mutex 9

1
sys/conf/files
View File

@ -618,6 +618,7 @@ kern/kern_acct.c standard
kern/kern_acl.c standard
kern/kern_cap.c standard
kern/kern_clock.c standard
kern/kern_condvar.c standard
kern/kern_conf.c standard
kern/kern_descrip.c standard
kern/kern_environment.c standard

1
sys/conf/options
View File

@ -471,6 +471,7 @@ KTR_ENTRIES opt_global.h
KTR_EXTEND opt_global.h
KTR_VERBOSE opt_ktr.h
MUTEX_DEBUG opt_global.h
CV_DEBUG opt_global.h
WITNESS opt_global.h
WITNESS_DDB opt_witness.h
WITNESS_SKIPSPIN opt_witness.h

547
sys/kern/kern_condvar.c Normal file
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@ -0,0 +1,547 @@
/*-
* 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/proc.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/condvar.h>
#include <sys/mutex.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, p) do { \
KASSERT((p) != NULL, ("%s: curproc NULL", __FUNCTION__)); \
KASSERT((p)->p_stat == SRUN, ("%s: not SRUN", __FUNCTION__)); \
KASSERT((cvp) != NULL, ("%s: cvp NULL", __FUNCTION__)); \
KASSERT((mp) != NULL, ("%s: mp NULL", __FUNCTION__)); \
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", __FUNCTION__)); \
} \
} while (0)
#define CV_SIGNAL_VALIDATE(cvp) do { \
if (!TAILQ_EMPTY(&(cvp)->cv_waitq)) { \
KASSERT(mtx_owned((cvp)->cv_mtx), \
("%s: Mutex not owned", __FUNCTION__)); \
} \
} 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", __FUNCTION__));
}
/*
* Common code for cv_wait* functions. All require sched_lock.
*/
/*
* Switch context.
*/
static __inline void
cv_switch(struct proc *p)
{
p->p_stat = SSLEEP;
p->p_stats->p_ru.ru_nvcsw++;
mi_switch();
CTR3(KTR_PROC, "cv_switch: resume proc %p (pid %d, %s)", p, p->p_pid,
p->p_comm);
}
/*
* Switch context, catching signals.
*/
static __inline int
cv_switch_catch(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, p->p_wchan will be 0 upon return from CURSIG.
*/
p->p_flag |= P_SINTR;
mtx_exit(&sched_lock, MTX_SPIN);
/* proc_lock(p); */
sig = CURSIG(p);
mtx_enter(&sched_lock, MTX_SPIN);
/* proc_unlock_noswitch(p); */
if (sig != 0) {
if (p->p_wchan != NULL)
cv_waitq_remove(p);
p->p_stat = SRUN;
} else if (p->p_wchan != NULL) {
cv_switch(p);
}
p->p_flag &= ~P_SINTR;
return sig;
}
/*
* Add a process to the wait queue of a condition variable.
*/
static __inline void
cv_waitq_add(struct cv *cvp, struct proc *p)
{
/*
* Process may be sitting on a slpque if asleep() was called, remove it
* before re-adding.
*/
if (p->p_wchan != NULL)
unsleep(p);
p->p_flag |= P_CVWAITQ;
p->p_wchan = cvp;
p->p_wmesg = cvp->cv_description;
p->p_slptime = 0;
p->p_nativepri = p->p_priority;
CTR3(KTR_PROC, "cv_waitq_add: proc %p (pid %d, %s)", p, p->p_pid,
p->p_comm);
TAILQ_INSERT_TAIL(&cvp->cv_waitq, p, p_slpq);
}
/*
* Wait on a condition variable. The current process 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 process. 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 proc *p;
WITNESS_SAVE_DECL(mp);
p = CURPROC;
#ifdef KTRACE
if (p && KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, p);
WITNESS_SLEEP(0, mp);
WITNESS_SAVE(mp, mp);
mtx_enter(&sched_lock, MTX_SPIN);
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_exit(&sched_lock, MTX_SPIN);
return;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_exit(mp, MTX_DEF | MTX_NOSWITCH);
cv_waitq_add(cvp, p);
cv_switch(p);
curpriority = p->p_usrpri;
mtx_exit(&sched_lock, MTX_SPIN);
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
PICKUP_GIANT();
mtx_enter(mp, MTX_DEF);
WITNESS_RESTORE(mp, mp);
}
/*
* Wait on a condition variable, allowing interruption by signals. Return 0 if
* the process 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 proc *p;
int rval;
int sig;
WITNESS_SAVE_DECL(mp);
p = CURPROC;
rval = 0;
#ifdef KTRACE
if (p && KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, p);
WITNESS_SLEEP(0, mp);
WITNESS_SAVE(mp, mp);
mtx_enter(&sched_lock, MTX_SPIN);
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_exit(&sched_lock, MTX_SPIN);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_exit(mp, MTX_DEF | MTX_NOSWITCH);
cv_waitq_add(cvp, p);
sig = cv_switch_catch(p);
curpriority = p->p_usrpri;
mtx_exit(&sched_lock, MTX_SPIN);
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
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
mtx_enter(mp, MTX_DEF);
WITNESS_RESTORE(mp, 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 proc *p;
int rval;
WITNESS_SAVE_DECL(mp);
p = CURPROC;
rval = 0;
#ifdef KTRACE
if (p && KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, p);
WITNESS_SLEEP(0, mp);
WITNESS_SAVE(mp, mp);
mtx_enter(&sched_lock, MTX_SPIN);
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_exit(&sched_lock, MTX_SPIN);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_exit(mp, MTX_DEF | MTX_NOSWITCH);
cv_waitq_add(cvp, p);
callout_reset(&p->p_slpcallout, timo, cv_timedwait_end, p);
cv_switch(p);
curpriority = p->p_usrpri;
if (p->p_flag & P_TIMEOUT) {
p->p_flag &= ~P_TIMEOUT;
rval = EWOULDBLOCK;
} else
callout_stop(&p->p_slpcallout);
mtx_exit(&sched_lock, MTX_SPIN);
#ifdef KTRACE
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
PICKUP_GIANT();
mtx_enter(mp, MTX_DEF);
WITNESS_RESTORE(mp, mp);
return (rval);
}
/*
* Wait on a condition variable for at most timo/hz seconds, allowing
* interruption by signals. Returns 0 if the process 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 proc *p;
int rval;
int sig;
WITNESS_SAVE_DECL(mp);
p = CURPROC;
rval = 0;
#ifdef KTRACE
if (p && KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 1, 0);
#endif
CV_ASSERT(cvp, mp, p);
WITNESS_SLEEP(0, mp);
WITNESS_SAVE(mp, mp);
mtx_enter(&sched_lock, MTX_SPIN);
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_exit(&sched_lock, MTX_SPIN);
return 0;
}
CV_WAIT_VALIDATE(cvp, mp);
DROP_GIANT_NOSWITCH();
mtx_exit(mp, MTX_DEF | MTX_NOSWITCH);
cv_waitq_add(cvp, p);
callout_reset(&p->p_slpcallout, timo, cv_timedwait_end, p);
sig = cv_switch_catch(p);
curpriority = p->p_usrpri;
if (p->p_flag & P_TIMEOUT) {
p->p_flag &= ~P_TIMEOUT;
rval = EWOULDBLOCK;
} else
callout_stop(&p->p_slpcallout);
mtx_exit(&sched_lock, MTX_SPIN);
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
if (KTRPOINT(p, KTR_CSW))
ktrcsw(p->p_tracep, 0, 0);
#endif
mtx_enter(mp, MTX_DEF);
WITNESS_RESTORE(mp, 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 proc *p;
p = TAILQ_FIRST(&cvp->cv_waitq);
KASSERT(p->p_wchan == cvp, ("%s: bogus wchan", __FUNCTION__));
KASSERT(p->p_flag & P_CVWAITQ, ("%s: not on waitq", __FUNCTION__));
TAILQ_REMOVE(&cvp->cv_waitq, p, p_slpq);
p->p_flag &= ~P_CVWAITQ;
p->p_wchan = 0;
if (p->p_stat == SSLEEP) {
/* OPTIMIZED EXPANSION OF setrunnable(p); */
CTR3(KTR_PROC, "cv_signal: proc %p (pid %d, %s)",
p, p->p_pid, p->p_comm);
if (p->p_slptime > 1)
updatepri(p);
p->p_slptime = 0;
p->p_stat = SRUN;
if (p->p_flag & P_INMEM) {
setrunqueue(p);
maybe_resched(p);
} else {
p->p_flag |= P_SWAPINREQ;
wakeup(&proc0);
}
/* END INLINE EXPANSION */
}
}
/*
* Signal a condition variable, wakes up one waiting process. 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 processes
* 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", __FUNCTION__));
mtx_enter(&sched_lock, MTX_SPIN);
if (!TAILQ_EMPTY(&cvp->cv_waitq)) {
CV_SIGNAL_VALIDATE(cvp);
cv_wakeup(cvp);
}
mtx_exit(&sched_lock, MTX_SPIN);
}
/*
* Broadcast a signal to a condition variable. Wakes up all waiting processes.
* 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", __FUNCTION__));
mtx_enter(&sched_lock, MTX_SPIN);
CV_SIGNAL_VALIDATE(cvp);
while (!TAILQ_EMPTY(&cvp->cv_waitq))
cv_wakeup(cvp);
mtx_exit(&sched_lock, MTX_SPIN);
}
/*
* Remove a process from the wait queue of its condition variable. This may be
* called externally.
*/
void
cv_waitq_remove(struct proc *p)
{
struct cv *cvp;
mtx_enter(&sched_lock, MTX_SPIN);
if ((cvp = p->p_wchan) != NULL && p->p_flag & P_CVWAITQ) {
TAILQ_REMOVE(&cvp->cv_waitq, p, p_slpq);
p->p_flag &= ~P_CVWAITQ;
p->p_wchan = NULL;
}
mtx_exit(&sched_lock, MTX_SPIN);
}
/*
* Timeout function for cv_timedwait. Put the process on the runqueue and set
* its timeout flag.
*/
static void
cv_timedwait_end(void *arg)
{
struct proc *p;
p = arg;
CTR3(KTR_PROC, "cv_timedwait_end: proc %p (pid %d, %s)", p, p->p_pid,
p->p_comm);
mtx_enter(&sched_lock, MTX_SPIN);
if (p->p_wchan != NULL) {
if (p->p_stat == SSLEEP)
setrunnable(p);
else
cv_waitq_remove(p);
p->p_flag |= P_TIMEOUT;
}
mtx_exit(&sched_lock, MTX_SPIN);
}

9
sys/kern/kern_sig.c
View File

@ -56,6 +56,7 @@
#include <sys/acct.h>
#include <sys/fcntl.h>
#include <sys/ipl.h>
#include <sys/condvar.h>
#include <sys/mutex.h>
#include <sys/wait.h>
#include <sys/ktr.h>
@ -1229,8 +1230,12 @@ psignal(p, sig)
* the process runnable, leave it stopped.
*/
mtx_enter(&sched_lock, MTX_SPIN);
if (p->p_wchan && p->p_flag & P_SINTR)
unsleep(p);
if (p->p_wchan && p->p_flag & P_SINTR) {
if (p->p_flag & P_CVWAITQ)
cv_waitq_remove(p);
else
unsleep(p);
}
mtx_exit(&sched_lock, MTX_SPIN);
goto out;

14
sys/kern/kern_synch.c
View File

@ -47,6 +47,7 @@
#include <sys/ipl.h>
#include <sys/kernel.h>
#include <sys/ktr.h>
#include <sys/condvar.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/signalvar.h>
@ -77,10 +78,8 @@ static struct callout roundrobin_callout;
static int curpriority_cmp __P((struct proc *p));
static void endtsleep __P((void *));
static void maybe_resched __P((struct proc *chk));
static void roundrobin __P((void *arg));
static void schedcpu __P((void *arg));
static void updatepri __P((struct proc *p));
static int
sysctl_kern_quantum(SYSCTL_HANDLER_ARGS)
@ -130,7 +129,7 @@ curpriority_cmp(p)
* Arrange to reschedule if necessary, taking the priorities and
* schedulers into account.
*/
static void
void
maybe_resched(chk)
struct proc *chk;
{
@ -358,7 +357,7 @@ schedcpu(arg)
* For all load averages >= 1 and max p_estcpu of 255, sleeping for at
* least six times the loadfactor will decay p_estcpu to zero.
*/
static void
void
updatepri(p)
register struct proc *p;
{
@ -993,8 +992,11 @@ setrunnable(p)
default:
panic("setrunnable");
case SSTOP:
case SSLEEP:
unsleep(p); /* e.g. when sending signals */
case SSLEEP: /* e.g. when sending signals */
if (p->p_flag & P_CVWAITQ)
cv_waitq_remove(p);
else
unsleep(p);
break;
case SIDL:

75
sys/sys/condvar.h Normal file
View File

@ -0,0 +1,75 @@
/*-
* 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.
*
* $FreeBSD$
*/
#ifndef _SYS_CONDVAR_H_
#define _SYS_CONDVAR_H_
#ifndef LOCORE
#include <sys/queue.h>
struct mtx;
struct proc;
TAILQ_HEAD(cv_waitq, proc);
/*
* Condition variable.
*/
struct cv {
struct cv_waitq cv_waitq; /* Queue of condition waiters. */
struct mtx *cv_mtx; /*
* Mutex passed in by cv_*wait*(),
* currently only used for CV_DEBUG.
*/
const char *cv_description;
};
#ifdef _KERNEL
#define CV_DECLARE(modifiers, name, descr) \
static const char __cv_descr_##name[] = descr; \
modifiers struct cv name = {{NULL, NULL}, NULL, __cv_descr_##name}
void cv_init(struct cv *cvp, const char *desc);
void cv_destroy(struct cv *cvp);
void cv_wait(struct cv *cvp, struct mtx *mp);
int cv_wait_sig(struct cv *cvp, struct mtx *mp);
int cv_timedwait(struct cv *cvp, struct mtx *mp, int timo);
int cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo);
void cv_signal(struct cv *cvp);
void cv_broadcast(struct cv *cvp);
void cv_waitq_remove(struct proc *p);
#define cv_waitq_empty(cvp) (TAILQ_EMPTY(&cvp->cv_waitq))
#define cv_wmesg(cvp) ((cvp)->cv_description)
#endif /* _KERNEL */
#endif /* !LOCORE */
#endif /* _SYS_CONDVAR_H_ */

4
sys/sys/proc.h
View File

@ -313,6 +313,8 @@ struct proc {
#define P_OLDMASK 0x2000000 /* Need to restore mask after suspend. */
#define P_ALTSTACK 0x4000000 /* Have alternate signal stack. */
#define P_CVWAITQ 0x8000000 /* proces is on a cv_waitq (not slpq) */
#define P_MAGIC 0xbeefface
#define P_CAN_SEE 1
@ -520,6 +522,8 @@ void cpu_idle __P((void));
void cpu_switch __P((void));
void cpu_throw __P((void)) __dead2;
void unsleep __P((struct proc *));
void updatepri __P((struct proc *));
void maybe_resched __P((struct proc *));
void cpu_exit __P((struct proc *)) __dead2;
void exit1 __P((struct proc *, int)) __dead2;