/* * Copyright (c) 2001 Jake Burkholder * 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: head/sys/kern/kern_switch.c 74914 2001-03-28 09:17:56Z jhb $ */ #include #include #include #include #include #include #include #include /* * Global run queue. */ static struct runq runq; SYSINIT(runq, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, runq_init, &runq) /* * Wrappers which implement old interface; act on global run queue. */ struct proc * chooseproc(void) { return runq_choose(&runq); } int procrunnable(void) { return runq_check(&runq); } void remrunqueue(struct proc *p) { runq_remove(&runq, p); } void setrunqueue(struct proc *p) { runq_add(&runq, p); } /* * 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]) - 1) + (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); } #ifdef INVARIANT_SUPPORT /* * Return true if the specified process is already in the run queue. */ static __inline int runq_find(struct runq *rq, struct proc *p) { struct proc *p2; int i; mtx_assert(&sched_lock, MA_OWNED); for (i = 0; i < RQB_LEN; i++) TAILQ_FOREACH(p2, &rq->rq_queues[i], p_procq) if (p2 == p) return 1; return 0; } #endif /* * Add the process to the queue specified by its priority, and set the * corresponding status bit. */ void runq_add(struct runq *rq, struct proc *p) { struct rqhead *rqh; int pri; mtx_assert(&sched_lock, MA_OWNED); KASSERT(p->p_stat == SRUN, ("runq_add: proc %p (%s) not SRUN", p, p->p_comm)); KASSERT(runq_find(rq, p) == 0, ("runq_add: proc %p (%s) already in run queue", p, p->p_comm)); pri = p->p_pri.pri_level / RQ_PPQ; p->p_rqindex = pri; runq_setbit(rq, pri); rqh = &rq->rq_queues[pri]; CTR4(KTR_RUNQ, "runq_add: p=%p pri=%d %d rqh=%p", p, p->p_pri.pri_level, pri, rqh); TAILQ_INSERT_TAIL(rqh, p, p_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); } /* * Find and remove the highest priority process from the run queue. * If there are no runnable processes, the per-cpu idle process is * returned. Will not return NULL under any circumstances. */ struct proc * runq_choose(struct runq *rq) { struct rqhead *rqh; struct proc *p; int pri; mtx_assert(&sched_lock, MA_OWNED); if ((pri = runq_findbit(rq)) != -1) { rqh = &rq->rq_queues[pri]; p = TAILQ_FIRST(rqh); KASSERT(p != NULL, ("runq_choose: no proc on busy queue")); KASSERT(p->p_stat == SRUN, ("runq_chose: process %d(%s) in state %d", p->p_pid, p->p_comm, p->p_stat)); CTR3(KTR_RUNQ, "runq_choose: pri=%d p=%p rqh=%p", pri, p, rqh); TAILQ_REMOVE(rqh, p, p_procq); if (TAILQ_EMPTY(rqh)) { CTR0(KTR_RUNQ, "runq_choose: empty"); runq_clrbit(rq, pri); } return (p); } CTR1(KTR_RUNQ, "runq_choose: idleproc pri=%d", pri); return (PCPU_GET(idleproc)); } /* * 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]); } /* * Remove the process from the queue specified by its priority, and clear the * corresponding status bit if the queue becomes empty. */ void runq_remove(struct runq *rq, struct proc *p) { struct rqhead *rqh; int pri; mtx_assert(&sched_lock, MA_OWNED); pri = p->p_rqindex; rqh = &rq->rq_queues[pri]; CTR4(KTR_RUNQ, "runq_remove: p=%p pri=%d %d rqh=%p", p, p->p_pri.pri_level, pri, rqh); KASSERT(p != NULL, ("runq_remove: no proc on busy queue")); TAILQ_REMOVE(rqh, p, p_procq); if (TAILQ_EMPTY(rqh)) { CTR0(KTR_RUNQ, "runq_remove: empty"); runq_clrbit(rq, pri); } }