thread stage 7: Implement basic LWKTs, use a straight round-robin model for
[dragonfly.git] / sys / kern / lwkt_thread.c
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1/*
2 * Copyright (c) 2003 Matthew Dillon <dillon@backplane.com>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: src/sys/kern/kern_switch.c,v 1.3.2.1 2000/05/16 06:58:12 dillon Exp $
27 * $DragonFly: src/sys/kern/lwkt_thread.c,v 1.1 2003/06/20 02:09:56 dillon Exp $
28 */
29
30#include <sys/param.h>
31#include <sys/systm.h>
32#include <sys/kernel.h>
33#include <sys/proc.h>
34#include <sys/rtprio.h>
35#include <sys/queue.h>
36
37/*
38 * LWKTs operate on a per-cpu basis
39 *
40 * YYY implement strict priorities & round-robin at the same priority
41 */
42void
43lwkt_gdinit(struct globaldata *gd)
44{
45 TAILQ_INIT(&gd->gd_tdrunq);
46}
47
48/*
49 * Switch to the next runnable lwkt. If no LWKTs are runnable then
50 * switch to the idlethread.
51 */
52void
53lwkt_switch(void)
54{
55 thread_t ntd;
56
57 if ((ntd = TAILQ_FIRST(&mycpu->gd_tdrunq)) != NULL) {
58 TAILQ_REMOVE(&mycpu->gd_tdrunq, ntd, td_threadq);
59 TAILQ_INSERT_TAIL(&mycpu->gd_tdrunq, ntd, td_threadq);
60 if (curthread != ntd)
61 curthread->td_switch(ntd);
62 } else {
63 if (curthread != &mycpu->gd_idlethread)
64 curthread->td_switch(&mycpu->gd_idlethread);
65 }
66}
67
68#if 0
69/*
70 * Switch to the next runnable lwkt preemptively ?
71 */
72void
73lwkt_preempt(void)
74{
75}
76#endif
77
78/*
79 * Schedule an LWKT. You can legally schedule yourself.
80 */
81void
82lwkt_schedule(thread_t td)
83{
84 if ((td->td_flags & TDF_RUNQ) == 0) {
85#if 0
86 if (td->td_flags & TDF_WAITQ) {
87 TAILQ_REMOVE(td->td_waitq, td, td_threadq);
88 td->td_flags &= ~TDF_WAITQ;
89 }
90#endif
91 td->td_flags |= TDF_RUNQ;
92 TAILQ_INSERT_TAIL(&mycpu->gd_tdrunq, td, td_threadq);
93 }
94}
95
96/*
97 * Deschedule an LWKT. You can legally deschedule yourself, but if you
98 * are preempted the thread will automatically be rescheduled. Preemption
99 * must be disabled (e.g. splhi()) to avoid unexpected rescheduling of
100 * the thread.
101 */
102void
103lwkt_deschedule(thread_t td)
104{
105 if (td->td_flags & TDF_RUNQ) {
106 TAILQ_REMOVE(&mycpu->gd_tdrunq, td, td_threadq);
107 td->td_flags &= ~TDF_RUNQ;
108 }
109}
110