1016 lines
28 KiB
C
1016 lines
28 KiB
C
/*-
|
|
* Copyright (c) 2001 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.
|
|
*/
|
|
|
|
/***
|
|
Here is the logic..
|
|
|
|
If there are N processors, then there are at most N KSEs (kernel
|
|
schedulable entities) working to process threads that belong to a
|
|
KSEGROUP (kg). If there are X of these KSEs actually running at the
|
|
moment in question, then there are at most M (N-X) of these KSEs on
|
|
the run queue, as running KSEs are not on the queue.
|
|
|
|
Runnable threads are queued off the KSEGROUP in priority order.
|
|
If there are M or more threads runnable, the top M threads
|
|
(by priority) are 'preassigned' to the M KSEs not running. The KSEs take
|
|
their priority from those threads and are put on the run queue.
|
|
|
|
The last thread that had a priority high enough to have a KSE associated
|
|
with it, AND IS ON THE RUN QUEUE is pointed to by
|
|
kg->kg_last_assigned. If no threads queued off the KSEGROUP have KSEs
|
|
assigned as all the available KSEs are activly running, or because there
|
|
are no threads queued, that pointer is NULL.
|
|
|
|
When a KSE is removed from the run queue to become runnable, we know
|
|
it was associated with the highest priority thread in the queue (at the head
|
|
of the queue). If it is also the last assigned we know M was 1 and must
|
|
now be 0. Since the thread is no longer queued that pointer must be
|
|
removed from it. Since we know there were no more KSEs available,
|
|
(M was 1 and is now 0) and since we are not FREEING our KSE
|
|
but using it, we know there are STILL no more KSEs available, we can prove
|
|
that the next thread in the ksegrp list will not have a KSE to assign to
|
|
it, so we can show that the pointer must be made 'invalid' (NULL).
|
|
|
|
The pointer exists so that when a new thread is made runnable, it can
|
|
have its priority compared with the last assigned thread to see if
|
|
it should 'steal' its KSE or not.. i.e. is it 'earlier'
|
|
on the list than that thread or later.. If it's earlier, then the KSE is
|
|
removed from the last assigned (which is now not assigned a KSE)
|
|
and reassigned to the new thread, which is placed earlier in the list.
|
|
The pointer is then backed up to the previous thread (which may or may not
|
|
be the new thread).
|
|
|
|
When a thread sleeps or is removed, the KSE becomes available and if there
|
|
are queued threads that are not assigned KSEs, the highest priority one of
|
|
them is assigned the KSE, which is then placed back on the run queue at
|
|
the approipriate place, and the kg->kg_last_assigned pointer is adjusted down
|
|
to point to it.
|
|
|
|
The following diagram shows 2 KSEs and 3 threads from a single process.
|
|
|
|
RUNQ: --->KSE---KSE--... (KSEs queued at priorities from threads)
|
|
\ \____
|
|
\ \
|
|
KSEGROUP---thread--thread--thread (queued in priority order)
|
|
\ /
|
|
\_______________/
|
|
(last_assigned)
|
|
|
|
The result of this scheme is that the M available KSEs are always
|
|
queued at the priorities they have inherrited from the M highest priority
|
|
threads for that KSEGROUP. If this situation changes, the KSEs are
|
|
reassigned to keep this true.
|
|
***/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include "opt_sched.h"
|
|
|
|
#ifndef KERN_SWITCH_INCLUDE
|
|
#include <sys/param.h>
|
|
#include <sys/systm.h>
|
|
#include <sys/kdb.h>
|
|
#include <sys/kernel.h>
|
|
#include <sys/ktr.h>
|
|
#include <sys/lock.h>
|
|
#include <sys/mutex.h>
|
|
#include <sys/proc.h>
|
|
#include <sys/queue.h>
|
|
#include <sys/sched.h>
|
|
#else /* KERN_SWITCH_INCLUDE */
|
|
#if defined(SMP) && (defined(__i386__) || defined(__amd64__))
|
|
#include <sys/smp.h>
|
|
#endif
|
|
#if defined(SMP) && defined(SCHED_4BSD)
|
|
#include <sys/sysctl.h>
|
|
#endif
|
|
|
|
#ifdef FULL_PREEMPTION
|
|
#ifndef PREEMPTION
|
|
#error "The FULL_PREEMPTION option requires the PREEMPTION option"
|
|
#endif
|
|
#endif
|
|
|
|
CTASSERT((RQB_BPW * RQB_LEN) == RQ_NQS);
|
|
|
|
#define td_kse td_sched
|
|
|
|
/*
|
|
* kern.sched.preemption allows user space to determine if preemption support
|
|
* is compiled in or not. It is not currently a boot or runtime flag that
|
|
* can be changed.
|
|
*/
|
|
#ifdef PREEMPTION
|
|
static int kern_sched_preemption = 1;
|
|
#else
|
|
static int kern_sched_preemption = 0;
|
|
#endif
|
|
SYSCTL_INT(_kern_sched, OID_AUTO, preemption, CTLFLAG_RD,
|
|
&kern_sched_preemption, 0, "Kernel preemption enabled");
|
|
|
|
/************************************************************************
|
|
* Functions that manipulate runnability from a thread perspective. *
|
|
************************************************************************/
|
|
/*
|
|
* Select the KSE that will be run next. From that find the thread, and
|
|
* remove it from the KSEGRP's run queue. If there is thread clustering,
|
|
* this will be what does it.
|
|
*/
|
|
struct thread *
|
|
choosethread(void)
|
|
{
|
|
struct kse *ke;
|
|
struct thread *td;
|
|
struct ksegrp *kg;
|
|
|
|
#if defined(SMP) && (defined(__i386__) || defined(__amd64__))
|
|
if (smp_active == 0 && PCPU_GET(cpuid) != 0) {
|
|
/* Shutting down, run idlethread on AP's */
|
|
td = PCPU_GET(idlethread);
|
|
ke = td->td_kse;
|
|
CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
|
|
ke->ke_flags |= KEF_DIDRUN;
|
|
TD_SET_RUNNING(td);
|
|
return (td);
|
|
}
|
|
#endif
|
|
|
|
retry:
|
|
ke = sched_choose();
|
|
if (ke) {
|
|
td = ke->ke_thread;
|
|
KASSERT((td->td_kse == ke), ("kse/thread mismatch"));
|
|
kg = ke->ke_ksegrp;
|
|
if (td->td_proc->p_flag & P_HADTHREADS) {
|
|
if (kg->kg_last_assigned == td) {
|
|
kg->kg_last_assigned = TAILQ_PREV(td,
|
|
threadqueue, td_runq);
|
|
}
|
|
TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
|
|
}
|
|
CTR2(KTR_RUNQ, "choosethread: td=%p pri=%d",
|
|
td, td->td_priority);
|
|
} else {
|
|
/* Simulate runq_choose() having returned the idle thread */
|
|
td = PCPU_GET(idlethread);
|
|
ke = td->td_kse;
|
|
CTR1(KTR_RUNQ, "choosethread: td=%p (idle)", td);
|
|
}
|
|
ke->ke_flags |= KEF_DIDRUN;
|
|
|
|
/*
|
|
* If we are in panic, only allow system threads,
|
|
* plus the one we are running in, to be run.
|
|
*/
|
|
if (panicstr && ((td->td_proc->p_flag & P_SYSTEM) == 0 &&
|
|
(td->td_flags & TDF_INPANIC) == 0)) {
|
|
/* note that it is no longer on the run queue */
|
|
TD_SET_CAN_RUN(td);
|
|
goto retry;
|
|
}
|
|
|
|
TD_SET_RUNNING(td);
|
|
return (td);
|
|
}
|
|
|
|
/*
|
|
* Given a surplus system slot, try assign a new runnable thread to it.
|
|
* Called from:
|
|
* sched_thread_exit() (local)
|
|
* sched_switch() (local)
|
|
* sched_thread_exit() (local)
|
|
* remrunqueue() (local) (not at the moment)
|
|
*/
|
|
static void
|
|
slot_fill(struct ksegrp *kg)
|
|
{
|
|
struct thread *td;
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
while (kg->kg_avail_opennings > 0) {
|
|
/*
|
|
* Find the first unassigned thread
|
|
*/
|
|
if ((td = kg->kg_last_assigned) != NULL)
|
|
td = TAILQ_NEXT(td, td_runq);
|
|
else
|
|
td = TAILQ_FIRST(&kg->kg_runq);
|
|
|
|
/*
|
|
* If we found one, send it to the system scheduler.
|
|
*/
|
|
if (td) {
|
|
kg->kg_last_assigned = td;
|
|
sched_add(td, SRQ_YIELDING);
|
|
CTR2(KTR_RUNQ, "slot_fill: td%p -> kg%p", td, kg);
|
|
} else {
|
|
/* no threads to use up the slots. quit now */
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
|
|
#ifdef SCHED_4BSD
|
|
/*
|
|
* Remove a thread from its KSEGRP's run queue.
|
|
* This in turn may remove it from a KSE if it was already assigned
|
|
* to one, possibly causing a new thread to be assigned to the KSE
|
|
* and the KSE getting a new priority.
|
|
*/
|
|
static void
|
|
remrunqueue(struct thread *td)
|
|
{
|
|
struct thread *td2, *td3;
|
|
struct ksegrp *kg;
|
|
struct kse *ke;
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
KASSERT((TD_ON_RUNQ(td)), ("remrunqueue: Bad state on run queue"));
|
|
kg = td->td_ksegrp;
|
|
ke = td->td_kse;
|
|
CTR1(KTR_RUNQ, "remrunqueue: td%p", td);
|
|
TD_SET_CAN_RUN(td);
|
|
/*
|
|
* If it is not a threaded process, take the shortcut.
|
|
*/
|
|
if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
|
|
/* remve from sys run queue and free up a slot */
|
|
sched_rem(td);
|
|
ke->ke_state = KES_THREAD;
|
|
return;
|
|
}
|
|
td3 = TAILQ_PREV(td, threadqueue, td_runq);
|
|
TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
|
|
if (ke->ke_state == KES_ONRUNQ) {
|
|
/*
|
|
* This thread has been assigned to the system run queue.
|
|
* We need to dissociate it and try assign the
|
|
* KSE to the next available thread. Then, we should
|
|
* see if we need to move the KSE in the run queues.
|
|
*/
|
|
sched_rem(td);
|
|
ke->ke_state = KES_THREAD;
|
|
td2 = kg->kg_last_assigned;
|
|
KASSERT((td2 != NULL), ("last assigned has wrong value"));
|
|
if (td2 == td)
|
|
kg->kg_last_assigned = td3;
|
|
/* slot_fill(kg); */ /* will replace it with another */
|
|
}
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Change the priority of a thread that is on the run queue.
|
|
*/
|
|
void
|
|
adjustrunqueue( struct thread *td, int newpri)
|
|
{
|
|
struct ksegrp *kg;
|
|
struct kse *ke;
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
KASSERT((TD_ON_RUNQ(td)), ("adjustrunqueue: Bad state on run queue"));
|
|
|
|
ke = td->td_kse;
|
|
CTR1(KTR_RUNQ, "adjustrunqueue: td%p", td);
|
|
/*
|
|
* If it is not a threaded process, take the shortcut.
|
|
*/
|
|
if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
|
|
/* We only care about the kse in the run queue. */
|
|
td->td_priority = newpri;
|
|
if (ke->ke_rqindex != (newpri / RQ_PPQ)) {
|
|
sched_rem(td);
|
|
sched_add(td, SRQ_BORING);
|
|
}
|
|
return;
|
|
}
|
|
|
|
/* It is a threaded process */
|
|
kg = td->td_ksegrp;
|
|
if (ke->ke_state == KES_ONRUNQ) {
|
|
if (kg->kg_last_assigned == td) {
|
|
kg->kg_last_assigned =
|
|
TAILQ_PREV(td, threadqueue, td_runq);
|
|
}
|
|
sched_rem(td);
|
|
}
|
|
TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
|
|
TD_SET_CAN_RUN(td);
|
|
td->td_priority = newpri;
|
|
setrunqueue(td, SRQ_BORING);
|
|
}
|
|
|
|
/*
|
|
* This function is called when a thread is about to be put on a
|
|
* ksegrp run queue because it has been made runnable or its
|
|
* priority has been adjusted and the ksegrp does not have a
|
|
* free kse slot. It determines if a thread from the same ksegrp
|
|
* should be preempted. If so, it tries to switch threads
|
|
* if the thread is on the same cpu or notifies another cpu that
|
|
* it should switch threads.
|
|
*/
|
|
|
|
static void
|
|
maybe_preempt_in_ksegrp(struct thread *td)
|
|
#if !defined(SMP)
|
|
{
|
|
struct thread *running_thread;
|
|
|
|
#ifndef FULL_PREEMPTION
|
|
int pri;
|
|
pri = td->td_priority;
|
|
if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD))
|
|
return;
|
|
#endif
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
running_thread = curthread;
|
|
|
|
if (running_thread->td_ksegrp != td->td_ksegrp)
|
|
return;
|
|
|
|
if (td->td_priority >= running_thread->td_priority)
|
|
return;
|
|
#ifdef PREEMPTION
|
|
if (running_thread->td_critnest > 1)
|
|
running_thread->td_owepreempt = 1;
|
|
else
|
|
mi_switch(SW_INVOL, NULL);
|
|
|
|
#else
|
|
running_thread->td_flags |= TDF_NEEDRESCHED;
|
|
#endif
|
|
return;
|
|
}
|
|
|
|
#else /* SMP */
|
|
{
|
|
struct thread *running_thread;
|
|
int worst_pri;
|
|
struct ksegrp *kg;
|
|
cpumask_t cpumask,dontuse;
|
|
struct pcpu *pc;
|
|
struct pcpu *best_pcpu;
|
|
struct thread *cputhread;
|
|
|
|
#ifndef FULL_PREEMPTION
|
|
int pri;
|
|
pri = td->td_priority;
|
|
if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD))
|
|
return;
|
|
#endif
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
|
|
running_thread = curthread;
|
|
|
|
#if !defined(KSEG_PEEMPT_BEST_CPU)
|
|
if (running_thread->td_ksegrp != td->td_ksegrp) {
|
|
#endif
|
|
kg = td->td_ksegrp;
|
|
|
|
/* if someone is ahead of this thread, wait our turn */
|
|
if (td != TAILQ_FIRST(&kg->kg_runq))
|
|
return;
|
|
|
|
worst_pri = td->td_priority;
|
|
best_pcpu = NULL;
|
|
dontuse = stopped_cpus | idle_cpus_mask;
|
|
|
|
/*
|
|
* Find a cpu with the worst priority that runs at thread from
|
|
* the same ksegrp - if multiple exist give first the last run
|
|
* cpu and then the current cpu priority
|
|
*/
|
|
|
|
SLIST_FOREACH(pc, &cpuhead, pc_allcpu) {
|
|
cpumask = pc->pc_cpumask;
|
|
cputhread = pc->pc_curthread;
|
|
|
|
if ((cpumask & dontuse) ||
|
|
cputhread->td_ksegrp != kg)
|
|
continue;
|
|
|
|
if (cputhread->td_priority > worst_pri) {
|
|
worst_pri = cputhread->td_priority;
|
|
best_pcpu = pc;
|
|
continue;
|
|
}
|
|
|
|
if (cputhread->td_priority == worst_pri &&
|
|
best_pcpu != NULL &&
|
|
(td->td_lastcpu == pc->pc_cpuid ||
|
|
(PCPU_GET(cpumask) == cpumask &&
|
|
td->td_lastcpu != best_pcpu->pc_cpuid)))
|
|
best_pcpu = pc;
|
|
}
|
|
|
|
/* Check if we need to preempt someone */
|
|
if (best_pcpu == NULL)
|
|
return;
|
|
|
|
if (PCPU_GET(cpuid) != best_pcpu->pc_cpuid) {
|
|
best_pcpu->pc_curthread->td_flags |= TDF_NEEDRESCHED;
|
|
ipi_selected(best_pcpu->pc_cpumask, IPI_AST);
|
|
return;
|
|
}
|
|
#if !defined(KSEG_PEEMPT_BEST_CPU)
|
|
}
|
|
#endif
|
|
|
|
if (td->td_priority >= running_thread->td_priority)
|
|
return;
|
|
#ifdef PREEMPTION
|
|
if (running_thread->td_critnest > 1)
|
|
running_thread->td_owepreempt = 1;
|
|
else
|
|
mi_switch(SW_INVOL, NULL);
|
|
|
|
#else
|
|
running_thread->td_flags |= TDF_NEEDRESCHED;
|
|
#endif
|
|
return;
|
|
}
|
|
#endif /* !SMP */
|
|
|
|
|
|
int limitcount;
|
|
void
|
|
setrunqueue(struct thread *td, int flags)
|
|
{
|
|
struct ksegrp *kg;
|
|
struct thread *td2;
|
|
struct thread *tda;
|
|
|
|
CTR3(KTR_RUNQ, "setrunqueue: td:%p kg:%p pid:%d",
|
|
td, td->td_ksegrp, td->td_proc->p_pid);
|
|
CTR5(KTR_SCHED, "setrunqueue: %p(%s) prio %d by %p(%s)",
|
|
td, td->td_proc->p_comm, td->td_priority, curthread,
|
|
curthread->td_proc->p_comm);
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
KASSERT((td->td_inhibitors == 0),
|
|
("setrunqueue: trying to run inhibitted thread"));
|
|
KASSERT((TD_CAN_RUN(td) || TD_IS_RUNNING(td)),
|
|
("setrunqueue: bad thread state"));
|
|
TD_SET_RUNQ(td);
|
|
kg = td->td_ksegrp;
|
|
if ((td->td_proc->p_flag & P_HADTHREADS) == 0) {
|
|
/*
|
|
* Common path optimisation: Only one of everything
|
|
* and the KSE is always already attached.
|
|
* Totally ignore the ksegrp run queue.
|
|
*/
|
|
if (kg->kg_avail_opennings != 1) {
|
|
if (limitcount < 1) {
|
|
limitcount++;
|
|
printf("pid %d: corrected slot count (%d->1)\n",
|
|
td->td_proc->p_pid, kg->kg_avail_opennings);
|
|
|
|
}
|
|
kg->kg_avail_opennings = 1;
|
|
}
|
|
sched_add(td, flags);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* If the concurrency has reduced, and we would go in the
|
|
* assigned section, then keep removing entries from the
|
|
* system run queue, until we are not in that section
|
|
* or there is room for us to be put in that section.
|
|
* What we MUST avoid is the case where there are threads of less
|
|
* priority than the new one scheduled, but it can not
|
|
* be scheduled itself. That would lead to a non contiguous set
|
|
* of scheduled threads, and everything would break.
|
|
*/
|
|
tda = kg->kg_last_assigned;
|
|
while ((kg->kg_avail_opennings <= 0) &&
|
|
(tda && (tda->td_priority > td->td_priority))) {
|
|
/*
|
|
* None free, but there is one we can commandeer.
|
|
*/
|
|
CTR2(KTR_RUNQ,
|
|
"setrunqueue: kg:%p: take slot from td: %p", kg, tda);
|
|
sched_rem(tda);
|
|
tda = kg->kg_last_assigned =
|
|
TAILQ_PREV(tda, threadqueue, td_runq);
|
|
}
|
|
|
|
/*
|
|
* Add the thread to the ksegrp's run queue at
|
|
* the appropriate place.
|
|
*/
|
|
TAILQ_FOREACH(td2, &kg->kg_runq, td_runq) {
|
|
if (td2->td_priority > td->td_priority) {
|
|
TAILQ_INSERT_BEFORE(td2, td, td_runq);
|
|
break;
|
|
}
|
|
}
|
|
if (td2 == NULL) {
|
|
/* We ran off the end of the TAILQ or it was empty. */
|
|
TAILQ_INSERT_TAIL(&kg->kg_runq, td, td_runq);
|
|
}
|
|
|
|
/*
|
|
* If we have a slot to use, then put the thread on the system
|
|
* run queue and if needed, readjust the last_assigned pointer.
|
|
* it may be that we need to schedule something anyhow
|
|
* even if the availabel slots are -ve so that
|
|
* all the items < last_assigned are scheduled.
|
|
*/
|
|
if (kg->kg_avail_opennings > 0) {
|
|
if (tda == NULL) {
|
|
/*
|
|
* No pre-existing last assigned so whoever is first
|
|
* gets the slot.. (maybe us)
|
|
*/
|
|
td2 = TAILQ_FIRST(&kg->kg_runq);
|
|
kg->kg_last_assigned = td2;
|
|
} else if (tda->td_priority > td->td_priority) {
|
|
td2 = td;
|
|
} else {
|
|
/*
|
|
* We are past last_assigned, so
|
|
* give the next slot to whatever is next,
|
|
* which may or may not be us.
|
|
*/
|
|
td2 = TAILQ_NEXT(tda, td_runq);
|
|
kg->kg_last_assigned = td2;
|
|
}
|
|
sched_add(td2, flags);
|
|
} else {
|
|
CTR3(KTR_RUNQ, "setrunqueue: held: td%p kg%p pid%d",
|
|
td, td->td_ksegrp, td->td_proc->p_pid);
|
|
if ((flags & SRQ_YIELDING) == 0)
|
|
maybe_preempt_in_ksegrp(td);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Kernel thread preemption implementation. Critical sections mark
|
|
* regions of code in which preemptions are not allowed.
|
|
*/
|
|
void
|
|
critical_enter(void)
|
|
{
|
|
struct thread *td;
|
|
|
|
td = curthread;
|
|
td->td_critnest++;
|
|
CTR4(KTR_CRITICAL, "critical_enter by thread %p (%ld, %s) to %d", td,
|
|
(long)td->td_proc->p_pid, td->td_proc->p_comm, td->td_critnest);
|
|
}
|
|
|
|
void
|
|
critical_exit(void)
|
|
{
|
|
struct thread *td;
|
|
|
|
td = curthread;
|
|
KASSERT(td->td_critnest != 0,
|
|
("critical_exit: td_critnest == 0"));
|
|
#ifdef PREEMPTION
|
|
if (td->td_critnest == 1) {
|
|
td->td_critnest = 0;
|
|
mtx_assert(&sched_lock, MA_NOTOWNED);
|
|
if (td->td_owepreempt) {
|
|
td->td_critnest = 1;
|
|
mtx_lock_spin(&sched_lock);
|
|
td->td_critnest--;
|
|
mi_switch(SW_INVOL, NULL);
|
|
mtx_unlock_spin(&sched_lock);
|
|
}
|
|
} else
|
|
#endif
|
|
td->td_critnest--;
|
|
|
|
|
|
CTR4(KTR_CRITICAL, "critical_exit by thread %p (%ld, %s) to %d", td,
|
|
(long)td->td_proc->p_pid, td->td_proc->p_comm, td->td_critnest);
|
|
}
|
|
|
|
/*
|
|
* This function is called when a thread is about to be put on run queue
|
|
* because it has been made runnable or its priority has been adjusted. It
|
|
* determines if the new thread should be immediately preempted to. If so,
|
|
* it switches to it and eventually returns true. If not, it returns false
|
|
* so that the caller may place the thread on an appropriate run queue.
|
|
*/
|
|
int
|
|
maybe_preempt(struct thread *td)
|
|
{
|
|
#ifdef PREEMPTION
|
|
struct thread *ctd;
|
|
int cpri, pri;
|
|
#endif
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
#ifdef PREEMPTION
|
|
/*
|
|
* The new thread should not preempt the current thread if any of the
|
|
* following conditions are true:
|
|
*
|
|
* - The kernel is in the throes of crashing (panicstr).
|
|
* - The current thread has a higher (numerically lower) or
|
|
* equivalent priority. Note that this prevents curthread from
|
|
* trying to preempt to itself.
|
|
* - It is too early in the boot for context switches (cold is set).
|
|
* - The current thread has an inhibitor set or is in the process of
|
|
* exiting. In this case, the current thread is about to switch
|
|
* out anyways, so there's no point in preempting. If we did,
|
|
* the current thread would not be properly resumed as well, so
|
|
* just avoid that whole landmine.
|
|
* - If the new thread's priority is not a realtime priority and
|
|
* the current thread's priority is not an idle priority and
|
|
* FULL_PREEMPTION is disabled.
|
|
*
|
|
* If all of these conditions are false, but the current thread is in
|
|
* a nested critical section, then we have to defer the preemption
|
|
* until we exit the critical section. Otherwise, switch immediately
|
|
* to the new thread.
|
|
*/
|
|
ctd = curthread;
|
|
KASSERT ((ctd->td_kse != NULL && ctd->td_kse->ke_thread == ctd),
|
|
("thread has no (or wrong) sched-private part."));
|
|
KASSERT((td->td_inhibitors == 0),
|
|
("maybe_preempt: trying to run inhibitted thread"));
|
|
pri = td->td_priority;
|
|
cpri = ctd->td_priority;
|
|
if (panicstr != NULL || pri >= cpri || cold /* || dumping */ ||
|
|
TD_IS_INHIBITED(ctd) || td->td_kse->ke_state != KES_THREAD)
|
|
return (0);
|
|
#ifndef FULL_PREEMPTION
|
|
if (!(pri >= PRI_MIN_ITHD && pri <= PRI_MAX_ITHD) &&
|
|
!(cpri >= PRI_MIN_IDLE))
|
|
return (0);
|
|
#endif
|
|
if (ctd->td_critnest > 1) {
|
|
CTR1(KTR_PROC, "maybe_preempt: in critical section %d",
|
|
ctd->td_critnest);
|
|
ctd->td_owepreempt = 1;
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Thread is runnable but not yet put on system run queue.
|
|
*/
|
|
MPASS(TD_ON_RUNQ(td));
|
|
MPASS(td->td_sched->ke_state != KES_ONRUNQ);
|
|
if (td->td_proc->p_flag & P_HADTHREADS) {
|
|
/*
|
|
* If this is a threaded process we actually ARE on the
|
|
* ksegrp run queue so take it off that first.
|
|
* Also undo any damage done to the last_assigned pointer.
|
|
* XXX Fix setrunqueue so this isn't needed
|
|
*/
|
|
struct ksegrp *kg;
|
|
|
|
kg = td->td_ksegrp;
|
|
if (kg->kg_last_assigned == td)
|
|
kg->kg_last_assigned =
|
|
TAILQ_PREV(td, threadqueue, td_runq);
|
|
TAILQ_REMOVE(&kg->kg_runq, td, td_runq);
|
|
}
|
|
|
|
TD_SET_RUNNING(td);
|
|
CTR3(KTR_PROC, "preempting to thread %p (pid %d, %s)\n", td,
|
|
td->td_proc->p_pid, td->td_proc->p_comm);
|
|
mi_switch(SW_INVOL|SW_PREEMPT, td);
|
|
return (1);
|
|
#else
|
|
return (0);
|
|
#endif
|
|
}
|
|
|
|
#if 0
|
|
#ifndef PREEMPTION
|
|
/* XXX: There should be a non-static version of this. */
|
|
static void
|
|
printf_caddr_t(void *data)
|
|
{
|
|
printf("%s", (char *)data);
|
|
}
|
|
static char preempt_warning[] =
|
|
"WARNING: Kernel preemption is disabled, expect reduced performance.\n";
|
|
SYSINIT(preempt_warning, SI_SUB_COPYRIGHT, SI_ORDER_ANY, printf_caddr_t,
|
|
preempt_warning)
|
|
#endif
|
|
#endif
|
|
|
|
/************************************************************************
|
|
* SYSTEM RUN QUEUE manipulations and tests *
|
|
************************************************************************/
|
|
/*
|
|
* Initialize a run structure.
|
|
*/
|
|
void
|
|
runq_init(struct runq *rq)
|
|
{
|
|
int i;
|
|
|
|
bzero(rq, sizeof *rq);
|
|
for (i = 0; i < RQ_NQS; i++)
|
|
TAILQ_INIT(&rq->rq_queues[i]);
|
|
}
|
|
|
|
/*
|
|
* Clear the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is empty.
|
|
*/
|
|
static __inline void
|
|
runq_clrbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Find the index of the first non-empty run queue. This is done by
|
|
* scanning the status bits, a set bit indicates a non-empty queue.
|
|
*/
|
|
static __inline int
|
|
runq_findbit(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int pri;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
pri = RQB_FFS(rqb->rqb_bits[i]) + (i << RQB_L2BPW);
|
|
CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
|
|
rqb->rqb_bits[i], i, pri);
|
|
return (pri);
|
|
}
|
|
|
|
return (-1);
|
|
}
|
|
|
|
/*
|
|
* Set the status bit of the queue corresponding to priority level pri,
|
|
* indicating that it is non-empty.
|
|
*/
|
|
static __inline void
|
|
runq_setbit(struct runq *rq, int pri)
|
|
{
|
|
struct rqbits *rqb;
|
|
|
|
rqb = &rq->rq_status;
|
|
CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
|
|
rqb->rqb_bits[RQB_WORD(pri)],
|
|
rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
|
|
RQB_BIT(pri), RQB_WORD(pri));
|
|
rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
|
|
}
|
|
|
|
/*
|
|
* Add the KSE to the queue specified by its priority, and set the
|
|
* corresponding status bit.
|
|
*/
|
|
void
|
|
runq_add(struct runq *rq, struct kse *ke, int flags)
|
|
{
|
|
struct rqhead *rqh;
|
|
int pri;
|
|
|
|
pri = ke->ke_thread->td_priority / RQ_PPQ;
|
|
ke->ke_rqindex = pri;
|
|
runq_setbit(rq, pri);
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR5(KTR_RUNQ, "runq_add: td=%p ke=%p pri=%d %d rqh=%p",
|
|
ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
|
|
if (flags & SRQ_PREEMPTED) {
|
|
TAILQ_INSERT_HEAD(rqh, ke, ke_procq);
|
|
} else {
|
|
TAILQ_INSERT_TAIL(rqh, ke, ke_procq);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Return true if there are runnable processes of any priority on the run
|
|
* queue, false otherwise. Has no side effects, does not modify the run
|
|
* queue structure.
|
|
*/
|
|
int
|
|
runq_check(struct runq *rq)
|
|
{
|
|
struct rqbits *rqb;
|
|
int i;
|
|
|
|
rqb = &rq->rq_status;
|
|
for (i = 0; i < RQB_LEN; i++)
|
|
if (rqb->rqb_bits[i]) {
|
|
CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
|
|
rqb->rqb_bits[i], i);
|
|
return (1);
|
|
}
|
|
CTR0(KTR_RUNQ, "runq_check: empty");
|
|
|
|
return (0);
|
|
}
|
|
|
|
#if defined(SMP) && defined(SCHED_4BSD)
|
|
int runq_fuzz = 1;
|
|
SYSCTL_INT(_kern_sched, OID_AUTO, runq_fuzz, CTLFLAG_RW, &runq_fuzz, 0, "");
|
|
#endif
|
|
|
|
/*
|
|
* Find the highest priority process on the run queue.
|
|
*/
|
|
struct kse *
|
|
runq_choose(struct runq *rq)
|
|
{
|
|
struct rqhead *rqh;
|
|
struct kse *ke;
|
|
int pri;
|
|
|
|
mtx_assert(&sched_lock, MA_OWNED);
|
|
while ((pri = runq_findbit(rq)) != -1) {
|
|
rqh = &rq->rq_queues[pri];
|
|
#if defined(SMP) && defined(SCHED_4BSD)
|
|
/* fuzz == 1 is normal.. 0 or less are ignored */
|
|
if (runq_fuzz > 1) {
|
|
/*
|
|
* In the first couple of entries, check if
|
|
* there is one for our CPU as a preference.
|
|
*/
|
|
int count = runq_fuzz;
|
|
int cpu = PCPU_GET(cpuid);
|
|
struct kse *ke2;
|
|
ke2 = ke = TAILQ_FIRST(rqh);
|
|
|
|
while (count-- && ke2) {
|
|
if (ke->ke_thread->td_lastcpu == cpu) {
|
|
ke = ke2;
|
|
break;
|
|
}
|
|
ke2 = TAILQ_NEXT(ke2, ke_procq);
|
|
}
|
|
} else
|
|
#endif
|
|
ke = TAILQ_FIRST(rqh);
|
|
KASSERT(ke != NULL, ("runq_choose: no proc on busy queue"));
|
|
CTR3(KTR_RUNQ,
|
|
"runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh);
|
|
return (ke);
|
|
}
|
|
CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri);
|
|
|
|
return (NULL);
|
|
}
|
|
|
|
/*
|
|
* Remove the KSE from the queue specified by its priority, and clear the
|
|
* corresponding status bit if the queue becomes empty.
|
|
* Caller must set ke->ke_state afterwards.
|
|
*/
|
|
void
|
|
runq_remove(struct runq *rq, struct kse *ke)
|
|
{
|
|
struct rqhead *rqh;
|
|
int pri;
|
|
|
|
KASSERT(ke->ke_proc->p_sflag & PS_INMEM,
|
|
("runq_remove: process swapped out"));
|
|
pri = ke->ke_rqindex;
|
|
rqh = &rq->rq_queues[pri];
|
|
CTR5(KTR_RUNQ, "runq_remove: td=%p, ke=%p pri=%d %d rqh=%p",
|
|
ke->ke_thread, ke, ke->ke_thread->td_priority, pri, rqh);
|
|
KASSERT(ke != NULL, ("runq_remove: no proc on busy queue"));
|
|
TAILQ_REMOVE(rqh, ke, ke_procq);
|
|
if (TAILQ_EMPTY(rqh)) {
|
|
CTR0(KTR_RUNQ, "runq_remove: empty");
|
|
runq_clrbit(rq, pri);
|
|
}
|
|
}
|
|
|
|
/****** functions that are temporarily here ***********/
|
|
#include <vm/uma.h>
|
|
extern struct mtx kse_zombie_lock;
|
|
|
|
/*
|
|
* Allocate scheduler specific per-process resources.
|
|
* The thread and ksegrp have already been linked in.
|
|
* In this case just set the default concurrency value.
|
|
*
|
|
* Called from:
|
|
* proc_init() (UMA init method)
|
|
*/
|
|
void
|
|
sched_newproc(struct proc *p, struct ksegrp *kg, struct thread *td)
|
|
{
|
|
|
|
/* This can go in sched_fork */
|
|
sched_init_concurrency(kg);
|
|
}
|
|
|
|
/*
|
|
* thread is being either created or recycled.
|
|
* Fix up the per-scheduler resources associated with it.
|
|
* Called from:
|
|
* sched_fork_thread()
|
|
* thread_dtor() (*may go away)
|
|
* thread_init() (*may go away)
|
|
*/
|
|
void
|
|
sched_newthread(struct thread *td)
|
|
{
|
|
struct td_sched *ke;
|
|
|
|
ke = (struct td_sched *) (td + 1);
|
|
bzero(ke, sizeof(*ke));
|
|
td->td_sched = ke;
|
|
ke->ke_thread = td;
|
|
ke->ke_state = KES_THREAD;
|
|
}
|
|
|
|
/*
|
|
* Set up an initial concurrency of 1
|
|
* and set the given thread (if given) to be using that
|
|
* concurrency slot.
|
|
* May be used "offline"..before the ksegrp is attached to the world
|
|
* and thus wouldn't need schedlock in that case.
|
|
* Called from:
|
|
* thr_create()
|
|
* proc_init() (UMA) via sched_newproc()
|
|
*/
|
|
void
|
|
sched_init_concurrency(struct ksegrp *kg)
|
|
{
|
|
|
|
CTR1(KTR_RUNQ,"kg %p init slots and concurrency to 1", kg);
|
|
kg->kg_concurrency = 1;
|
|
kg->kg_avail_opennings = 1;
|
|
}
|
|
|
|
/*
|
|
* Change the concurrency of an existing ksegrp to N
|
|
* Called from:
|
|
* kse_create()
|
|
* kse_exit()
|
|
* thread_exit()
|
|
* thread_single()
|
|
*/
|
|
void
|
|
sched_set_concurrency(struct ksegrp *kg, int concurrency)
|
|
{
|
|
|
|
CTR4(KTR_RUNQ,"kg %p set concurrency to %d, slots %d -> %d",
|
|
kg,
|
|
concurrency,
|
|
kg->kg_avail_opennings,
|
|
kg->kg_avail_opennings + (concurrency - kg->kg_concurrency));
|
|
kg->kg_avail_opennings += (concurrency - kg->kg_concurrency);
|
|
kg->kg_concurrency = concurrency;
|
|
}
|
|
|
|
/*
|
|
* Called from thread_exit() for all exiting thread
|
|
*
|
|
* Not to be confused with sched_exit_thread()
|
|
* that is only called from thread_exit() for threads exiting
|
|
* without the rest of the process exiting because it is also called from
|
|
* sched_exit() and we wouldn't want to call it twice.
|
|
* XXX This can probably be fixed.
|
|
*/
|
|
void
|
|
sched_thread_exit(struct thread *td)
|
|
{
|
|
|
|
SLOT_RELEASE(td->td_ksegrp);
|
|
slot_fill(td->td_ksegrp);
|
|
}
|
|
|
|
#endif /* KERN_SWITCH_INCLUDE */
|