299 lines
7.2 KiB
C
299 lines
7.2 KiB
C
/*
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* Copyright (c) 2001 Jake Burkholder <jake@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/queue.h>
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/*
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* Global run queue.
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*/
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static struct runq runq;
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SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq)
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/*
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* Wrappers which implement old interface; act on global run queue.
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*/
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struct thread *
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choosethread(void)
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{
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return (runq_choose(&runq)->ke_thread);
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}
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int
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procrunnable(void)
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{
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return runq_check(&runq);
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}
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void
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remrunqueue(struct thread *td)
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{
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runq_remove(&runq, td->td_kse);
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}
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void
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setrunqueue(struct thread *td)
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{
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runq_add(&runq, td->td_kse);
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}
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/* Critical sections that prevent preemption. */
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void
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critical_enter(void)
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{
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struct thread *td;
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td = curthread;
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if (td->td_critnest == 0)
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td->td_savecrit = cpu_critical_enter();
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td->td_critnest++;
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}
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void
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critical_exit(void)
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{
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struct thread *td;
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td = curthread;
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if (td->td_critnest == 1) {
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td->td_critnest = 0;
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cpu_critical_exit(td->td_savecrit);
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} else
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td->td_critnest--;
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}
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/*
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* Clear the status bit of the queue corresponding to priority level pri,
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* indicating that it is empty.
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*/
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static __inline void
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runq_clrbit(struct runq *rq, int pri)
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{
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struct rqbits *rqb;
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rqb = &rq->rq_status;
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CTR4(KTR_RUNQ, "runq_clrbit: bits=%#x %#x bit=%#x word=%d",
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rqb->rqb_bits[RQB_WORD(pri)],
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rqb->rqb_bits[RQB_WORD(pri)] & ~RQB_BIT(pri),
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RQB_BIT(pri), RQB_WORD(pri));
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rqb->rqb_bits[RQB_WORD(pri)] &= ~RQB_BIT(pri);
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}
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/*
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* Find the index of the first non-empty run queue. This is done by
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* scanning the status bits, a set bit indicates a non-empty queue.
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*/
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static __inline int
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runq_findbit(struct runq *rq)
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{
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struct rqbits *rqb;
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int pri;
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int i;
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rqb = &rq->rq_status;
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for (i = 0; i < RQB_LEN; i++)
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if (rqb->rqb_bits[i]) {
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pri = (RQB_FFS(rqb->rqb_bits[i]) - 1) +
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(i << RQB_L2BPW);
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CTR3(KTR_RUNQ, "runq_findbit: bits=%#x i=%d pri=%d",
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rqb->rqb_bits[i], i, pri);
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return (pri);
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}
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return (-1);
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}
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/*
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* Set the status bit of the queue corresponding to priority level pri,
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* indicating that it is non-empty.
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*/
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static __inline void
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runq_setbit(struct runq *rq, int pri)
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{
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struct rqbits *rqb;
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rqb = &rq->rq_status;
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CTR4(KTR_RUNQ, "runq_setbit: bits=%#x %#x bit=%#x word=%d",
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rqb->rqb_bits[RQB_WORD(pri)],
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rqb->rqb_bits[RQB_WORD(pri)] | RQB_BIT(pri),
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RQB_BIT(pri), RQB_WORD(pri));
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rqb->rqb_bits[RQB_WORD(pri)] |= RQB_BIT(pri);
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}
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#ifdef INVARIANT_SUPPORT
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/*
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* Return true if the specified process is already in the run queue.
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*/
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static __inline int
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runq_find(struct runq *rq, struct kse *ke)
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{
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struct kse *ke2;
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int i;
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mtx_assert(&sched_lock, MA_OWNED);
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for (i = 0; i < RQB_LEN; i++)
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TAILQ_FOREACH(ke2, &rq->rq_queues[i], ke_procq)
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if (ke2 == ke)
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return 1;
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return 0;
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}
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#endif
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/*
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* Add the process to the queue specified by its priority, and set the
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* corresponding status bit.
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*/
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void
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runq_add(struct runq *rq, struct kse *ke)
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{
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struct rqhead *rqh;
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int pri;
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#ifdef INVARIANTS
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struct proc *p = ke->ke_proc;
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#endif
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if (ke->ke_flags & KEF_ONRUNQ)
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return;
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mtx_assert(&sched_lock, MA_OWNED);
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KASSERT(p->p_stat == SRUN, ("runq_add: proc %p (%s) not SRUN",
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p, p->p_comm));
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KASSERT(runq_find(rq, ke) == 0,
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("runq_add: proc %p (%s) already in run queue", ke, p->p_comm));
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pri = ke->ke_thread->td_priority / RQ_PPQ;
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ke->ke_rqindex = pri;
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runq_setbit(rq, pri);
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rqh = &rq->rq_queues[pri];
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CTR4(KTR_RUNQ, "runq_add: p=%p pri=%d %d rqh=%p",
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ke->ke_proc, ke->ke_thread->td_priority, pri, rqh);
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TAILQ_INSERT_TAIL(rqh, ke, ke_procq);
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ke->ke_flags |= KEF_ONRUNQ;
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}
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/*
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* Return true if there are runnable processes of any priority on the run
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* queue, false otherwise. Has no side effects, does not modify the run
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* queue structure.
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*/
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int
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runq_check(struct runq *rq)
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{
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struct rqbits *rqb;
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int i;
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rqb = &rq->rq_status;
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for (i = 0; i < RQB_LEN; i++)
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if (rqb->rqb_bits[i]) {
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CTR2(KTR_RUNQ, "runq_check: bits=%#x i=%d",
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rqb->rqb_bits[i], i);
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return (1);
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}
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CTR0(KTR_RUNQ, "runq_check: empty");
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return (0);
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}
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/*
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* Find and remove the highest priority process from the run queue.
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* If there are no runnable processes, the per-cpu idle process is
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* returned. Will not return NULL under any circumstances.
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*/
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struct kse *
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runq_choose(struct runq *rq)
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{
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struct rqhead *rqh;
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struct kse *ke;
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int pri;
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mtx_assert(&sched_lock, MA_OWNED);
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if ((pri = runq_findbit(rq)) != -1) {
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rqh = &rq->rq_queues[pri];
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ke = TAILQ_FIRST(rqh);
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KASSERT(ke != NULL, ("runq_choose: no proc on busy queue"));
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KASSERT(ke->ke_proc->p_stat == SRUN,
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("runq_choose: process %d(%s) in state %d", ke->ke_proc->p_pid,
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ke->ke_proc->p_comm, ke->ke_proc->p_stat));
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CTR3(KTR_RUNQ, "runq_choose: pri=%d kse=%p rqh=%p", pri, ke, rqh);
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TAILQ_REMOVE(rqh, ke, ke_procq);
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if (TAILQ_EMPTY(rqh)) {
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CTR0(KTR_RUNQ, "runq_choose: empty");
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runq_clrbit(rq, pri);
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}
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ke->ke_flags &= ~KEF_ONRUNQ;
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return (ke);
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}
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CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri);
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return (PCPU_GET(idlethread)->td_kse);
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}
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/*
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* Initialize a run structure.
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*/
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void
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runq_init(struct runq *rq)
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{
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int i;
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bzero(rq, sizeof *rq);
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for (i = 0; i < RQ_NQS; i++)
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TAILQ_INIT(&rq->rq_queues[i]);
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}
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/*
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* Remove the process from the queue specified by its priority, and clear the
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* corresponding status bit if the queue becomes empty.
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*/
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void
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runq_remove(struct runq *rq, struct kse *ke)
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{
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struct rqhead *rqh;
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int pri;
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if (!(ke->ke_flags & KEF_ONRUNQ))
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return;
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mtx_assert(&sched_lock, MA_OWNED);
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pri = ke->ke_rqindex;
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rqh = &rq->rq_queues[pri];
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CTR4(KTR_RUNQ, "runq_remove: p=%p pri=%d %d rqh=%p",
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ke, ke->ke_thread->td_priority, pri, rqh);
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KASSERT(ke != NULL, ("runq_remove: no proc on busy queue"));
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TAILQ_REMOVE(rqh, ke, ke_procq);
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if (TAILQ_EMPTY(rqh)) {
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CTR0(KTR_RUNQ, "runq_remove: empty");
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runq_clrbit(rq, pri);
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}
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ke->ke_flags &= ~KEF_ONRUNQ;
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}
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