1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
|
/*
* Mach Operating System
* Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University.
* Copyright (c) 1993,1994 The University of Utah and
* the Computer Systems Laboratory (CSL).
* All rights reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON, THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF
* THIS SOFTWARE IN ITS "AS IS" CONDITION, AND DISCLAIM ANY LIABILITY
* OF ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF
* THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
/*
*
* This file contains routines to check whether an ast is needed.
*
* ast_check() - check whether ast is needed for interrupt or context
* switch. Usually called by clock interrupt handler.
*
*/
#include <cpus.h>
#include <mach_fixpri.h>
#include <norma_ipc.h>
#include <kern/ast.h>
#include <kern/counters.h>
#include "cpu_number.h"
#include <kern/queue.h>
#include <kern/sched.h>
#include <kern/sched_prim.h>
#include <kern/thread.h>
#include <kern/processor.h>
#include <machine/machspl.h> /* for splsched */
#if MACH_FIXPRI
#include <mach/policy.h>
#endif MACH_FIXPRI
volatile ast_t need_ast[NCPUS];
void
ast_init()
{
#ifndef MACHINE_AST
register int i;
for (i=0; i<NCPUS; i++)
need_ast[i] = 0;
#endif MACHINE_AST
}
void
ast_taken()
{
register thread_t self = current_thread();
register ast_t reasons;
/*
* Interrupts are still disabled.
* We must clear need_ast and then enable interrupts.
*/
reasons = need_ast[cpu_number()];
need_ast[cpu_number()] = AST_ZILCH;
(void) spl0();
/*
* These actions must not block.
*/
if (reasons & AST_NETWORK)
net_ast();
#if NORMA_IPC
if (reasons & AST_NETIPC)
netipc_ast();
#endif NORMA_IPC
/*
* Make darn sure that we don't call thread_halt_self
* or thread_block from the idle thread.
*/
if (self != current_processor()->idle_thread) {
#ifndef MIGRATING_THREADS
while (thread_should_halt(self))
thread_halt_self();
#endif
/*
* One of the previous actions might well have
* woken a high-priority thread, so we use
* csw_needed in addition to AST_BLOCK.
*/
if ((reasons & AST_BLOCK) ||
csw_needed(self, current_processor())) {
counter(c_ast_taken_block++);
thread_block(thread_exception_return);
}
}
}
void
ast_check()
{
register int mycpu = cpu_number();
register processor_t myprocessor;
register thread_t thread = current_thread();
register run_queue_t rq;
spl_t s = splsched();
/*
* Check processor state for ast conditions.
*/
myprocessor = cpu_to_processor(mycpu);
switch(myprocessor->state) {
case PROCESSOR_OFF_LINE:
case PROCESSOR_IDLE:
case PROCESSOR_DISPATCHING:
/*
* No ast.
*/
break;
#if NCPUS > 1
case PROCESSOR_ASSIGN:
case PROCESSOR_SHUTDOWN:
/*
* Need ast to force action thread onto processor.
*
* XXX Should check if action thread is already there.
*/
ast_on(mycpu, AST_BLOCK);
break;
#endif NCPUS > 1
case PROCESSOR_RUNNING:
/*
* Propagate thread ast to processor. If we already
* need an ast, don't look for more reasons.
*/
ast_propagate(thread, mycpu);
if (ast_needed(mycpu))
break;
/*
* Context switch check. The csw_needed macro isn't
* used here because the rq->low hint may be wrong,
* and fixing it here avoids an extra ast.
* First check the easy cases.
*/
if (thread->state & TH_SUSP || myprocessor->runq.count > 0) {
ast_on(mycpu, AST_BLOCK);
break;
}
/*
* Update lazy evaluated runq->low if only timesharing.
*/
#if MACH_FIXPRI
if (myprocessor->processor_set->policies & POLICY_FIXEDPRI) {
if (csw_needed(thread,myprocessor)) {
ast_on(mycpu, AST_BLOCK);
break;
}
else {
/*
* For fixed priority threads, set first_quantum
* so entire new quantum is used.
*/
if (thread->policy == POLICY_FIXEDPRI)
myprocessor->first_quantum = TRUE;
}
}
else {
#endif MACH_FIXPRI
rq = &(myprocessor->processor_set->runq);
if (!(myprocessor->first_quantum) && (rq->count > 0)) {
register queue_t q;
/*
* This is not the first quantum, and there may
* be something in the processor_set runq.
* Check whether low hint is accurate.
*/
q = rq->runq + *(volatile int *)&rq->low;
if (queue_empty(q)) {
register int i;
/*
* Need to recheck and possibly update hint.
*/
simple_lock(&rq->lock);
q = rq->runq + rq->low;
if (rq->count > 0) {
for (i = rq->low; i < NRQS; i++) {
if(!(queue_empty(q)))
break;
q++;
}
rq->low = i;
}
simple_unlock(&rq->lock);
}
if (rq->low <= thread->sched_pri) {
ast_on(mycpu, AST_BLOCK);
break;
}
}
#if MACH_FIXPRI
}
#endif MACH_FIXPRI
break;
default:
panic("ast_check: Bad processor state (cpu %d processor %08x) state: %d",
mycpu, myprocessor, myprocessor->state);
}
(void) splx(s);
}
|
