1 // SPDX-License-Identifier: GPL-2.0+
2
3 #include <exports.h>
4
5 /*
6 * Author: Arun Dharankar <ADharankar@ATTBI.Com>
7 *
8 * A very simple thread/schedular model:
9 * - only one master thread, and no parent child relation maintained
10 * - parent thread cannot be stopped or deleted
11 * - no permissions or credentials
12 * - no elaborate safety checks
13 * - cooperative multi threading
14 * - Simple round-robin scheduleing with no priorities
15 * - no metering/statistics collection
16 *
17 * Basic idea of implementing this is to allow more than one tests to
18 * execute "simultaneously".
19 *
20 * This may be modified such thread_yield may be called in syscalls, and
21 * timer interrupts.
22 */
23
24 #define MAX_THREADS 8
25
26 #define CTX_SIZE 512
27 #define STK_SIZE 8*1024
28
29 #define STATE_EMPTY 0
30 #define STATE_RUNNABLE 1
31 #define STATE_STOPPED 2
32 #define STATE_TERMINATED 2
33
34 #define MASTER_THREAD 0
35
36 #define RC_FAILURE (-1)
37 #define RC_SUCCESS (0)
38
39 typedef vu_char *jmp_ctx;
40 unsigned long setctxsp (vu_char *sp);
41 int ppc_setjmp(jmp_ctx env);
42 void ppc_longjmp(jmp_ctx env, int val);
43 #define setjmp ppc_setjmp
44 #define longjmp ppc_longjmp
45
46 struct lthread {
47 int state;
48 int retval;
49 char stack[STK_SIZE];
50 uchar context[CTX_SIZE];
51 int (*func) (void *);
52 void *arg;
53 };
54 static volatile struct lthread lthreads[MAX_THREADS];
55 static volatile int current_tid = MASTER_THREAD;
56
57 static uchar dbg = 0;
58
59 #define PDEBUG(fmt, args...) { \
60 if(dbg != 0) { \
61 printf("[%s %d %s]: ",__FILE__,__LINE__,__FUNCTION__);\
62 printf(fmt, ##args); \
63 printf("\n"); \
64 } \
65 }
66
67 static int testthread (void *);
68 static void sched_init (void);
69 static int thread_create (int (*func) (void *), void *arg);
70 static int thread_start (int id);
71 static void thread_yield (void);
72 static int thread_delete (int id);
73 static int thread_join (int *ret);
74
75 #if 0 /* not used yet */
76 static int thread_stop (int id);
77 #endif /* not used yet */
78
79 /* An example of schedular test */
80
81 #define NUMTHREADS 7
sched(int ac,char * av[])82 int sched (int ac, char *av[])
83 {
84 int i, j;
85 int tid[NUMTHREADS];
86 int names[NUMTHREADS];
87
88 app_startup(av);
89
90 sched_init ();
91
92 for (i = 0; i < NUMTHREADS; i++) {
93 names[i] = i;
94 j = thread_create (testthread, (void *) &names[i]);
95 if (j == RC_FAILURE)
96 printf ("schedtest: Failed to create thread %d\n", i);
97 if (j > 0) {
98 printf ("schedtest: Created thread with id %d, name %d\n",
99 j, i);
100 tid[i] = j;
101 }
102 }
103 printf ("schedtest: Threads created\n");
104
105 printf ("sched_test: function=0x%08x\n", (unsigned)testthread);
106 for (i = 0; i < NUMTHREADS; i++) {
107 printf ("schedtest: Setting thread %d runnable\n", tid[i]);
108 thread_start (tid[i]);
109 thread_yield ();
110 }
111 printf ("schedtest: Started %d threads\n", NUMTHREADS);
112
113 while (1) {
114 printf ("schedtest: Waiting for threads to complete\n");
115 if (tstc () && getc () == 0x3) {
116 printf ("schedtest: Aborting threads...\n");
117 for (i = 0; i < NUMTHREADS; i++) {
118 printf ("schedtest: Deleting thread %d\n", tid[i]);
119 thread_delete (tid[i]);
120 }
121 return RC_SUCCESS;
122 }
123 j = -1;
124 i = thread_join (&j);
125 if (i == RC_FAILURE) {
126 printf ("schedtest: No threads pending, "
127 "exiting schedular test\n");
128 return RC_SUCCESS;
129 }
130 printf ("schedtest: thread is %d returned %d\n", i, j);
131 thread_yield ();
132 }
133
134 return RC_SUCCESS;
135 }
136
testthread(void * name)137 static int testthread (void *name)
138 {
139 int i;
140
141 printf ("testthread: Begin executing thread, myname %d, &i=0x%08x\n",
142 *(int *) name, (unsigned)&i);
143
144 printf ("Thread %02d, i=%d\n", *(int *) name, i);
145
146 for (i = 0; i < 0xffff * (*(int *) name + 1); i++) {
147 if (tstc () && getc () == 0x3) {
148 printf ("testthread: myname %d terminating.\n",
149 *(int *) name);
150 return *(int *) name + 1;
151 }
152
153 if (i % 100 == 0)
154 thread_yield ();
155 }
156
157 printf ("testthread: returning %d, i=0x%x\n",
158 *(int *) name + 1, i);
159
160 return *(int *) name + 1;
161 }
162
sched_init(void)163 static void sched_init (void)
164 {
165 int i;
166
167 for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++)
168 lthreads[i].state = STATE_EMPTY;
169
170 current_tid = MASTER_THREAD;
171 lthreads[current_tid].state = STATE_RUNNABLE;
172 PDEBUG ("sched_init: master context = 0x%08x",
173 (unsigned)lthreads[current_tid].context);
174 return;
175 }
176
thread_yield(void)177 static void thread_yield (void)
178 {
179 static int i;
180
181 PDEBUG ("thread_yield: current tid=%d", current_tid);
182
183 #define SWITCH(new) \
184 if(lthreads[new].state == STATE_RUNNABLE) { \
185 PDEBUG("thread_yield: %d match, ctx=0x%08x", \
186 new, \
187 (unsigned)lthreads[current_tid].context); \
188 if(setjmp(lthreads[current_tid].context) == 0) { \
189 current_tid = new; \
190 PDEBUG("thread_yield: tid %d returns 0", \
191 new); \
192 longjmp(lthreads[new].context, 1); \
193 } else { \
194 PDEBUG("thread_yield: tid %d returns 1", \
195 new); \
196 return; \
197 } \
198 }
199
200 for (i = current_tid + 1; i < MAX_THREADS; i++) {
201 SWITCH (i);
202 }
203
204 if (current_tid != 0) {
205 for (i = 0; i <= current_tid; i++) {
206 SWITCH (i);
207 }
208 }
209
210 PDEBUG ("thread_yield: returning from thread_yield");
211 return;
212 }
213
thread_create(int (* func)(void *),void * arg)214 static int thread_create (int (*func) (void *), void *arg)
215 {
216 int i;
217
218 for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
219 if (lthreads[i].state == STATE_EMPTY) {
220 lthreads[i].state = STATE_STOPPED;
221 lthreads[i].func = func;
222 lthreads[i].arg = arg;
223 PDEBUG ("thread_create: returns new tid %d", i);
224 return i;
225 }
226 }
227
228 PDEBUG ("thread_create: returns failure");
229 return RC_FAILURE;
230 }
231
thread_delete(int id)232 static int thread_delete (int id)
233 {
234 if (id <= MASTER_THREAD || id > MAX_THREADS)
235 return RC_FAILURE;
236
237 if (current_tid == id)
238 return RC_FAILURE;
239
240 lthreads[id].state = STATE_EMPTY;
241 return RC_SUCCESS;
242 }
243
thread_launcher(void)244 static void thread_launcher (void)
245 {
246 PDEBUG ("thread_launcher: invoking func=0x%08x",
247 (unsigned)lthreads[current_tid].func);
248
249 lthreads[current_tid].retval =
250 lthreads[current_tid].func (lthreads[current_tid].arg);
251
252 PDEBUG ("thread_launcher: tid %d terminated", current_tid);
253
254 lthreads[current_tid].state = STATE_TERMINATED;
255 thread_yield ();
256 printf ("thread_launcher: should NEVER get here!\n");
257
258 return;
259 }
260
thread_start(int id)261 static int thread_start (int id)
262 {
263 PDEBUG ("thread_start: id=%d", id);
264 if (id <= MASTER_THREAD || id > MAX_THREADS) {
265 return RC_FAILURE;
266 }
267
268 if (lthreads[id].state != STATE_STOPPED)
269 return RC_FAILURE;
270
271 if (setjmp (lthreads[current_tid].context) == 0) {
272 lthreads[id].state = STATE_RUNNABLE;
273 current_tid = id;
274 PDEBUG ("thread_start: to be stack=0%08x",
275 (unsigned)lthreads[id].stack);
276 setctxsp ((vu_char *)<hreads[id].stack[STK_SIZE]);
277 thread_launcher ();
278 }
279
280 PDEBUG ("thread_start: Thread id=%d started, parent returns", id);
281
282 return RC_SUCCESS;
283 }
284
285 #if 0 /* not used so far */
286 static int thread_stop (int id)
287 {
288 if (id <= MASTER_THREAD || id >= MAX_THREADS)
289 return RC_FAILURE;
290
291 if (current_tid == id)
292 return RC_FAILURE;
293
294 lthreads[id].state = STATE_STOPPED;
295 return RC_SUCCESS;
296 }
297 #endif /* not used so far */
298
thread_join(int * ret)299 static int thread_join (int *ret)
300 {
301 int i, j = 0;
302
303 PDEBUG ("thread_join: *ret = %d", *ret);
304
305 if (!(*ret == -1 || *ret > MASTER_THREAD || *ret < MAX_THREADS)) {
306 PDEBUG ("thread_join: invalid tid %d", *ret);
307 return RC_FAILURE;
308 }
309
310 if (*ret == -1) {
311 PDEBUG ("Checking for tid = -1");
312 while (1) {
313 /* PDEBUG("thread_join: start while-loopn"); */
314 j = 0;
315 for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
316 if (lthreads[i].state == STATE_TERMINATED) {
317 *ret = lthreads[i].retval;
318 lthreads[i].state = STATE_EMPTY;
319 /* PDEBUG("thread_join: returning retval %d of tid %d",
320 ret, i); */
321 return RC_SUCCESS;
322 }
323
324 if (lthreads[i].state != STATE_EMPTY) {
325 PDEBUG ("thread_join: %d used slots tid %d state=%d",
326 j, i, lthreads[i].state);
327 j++;
328 }
329 }
330 if (j == 0) {
331 PDEBUG ("thread_join: all slots empty!");
332 return RC_FAILURE;
333 }
334 /* PDEBUG("thread_join: yielding"); */
335 thread_yield ();
336 /* PDEBUG("thread_join: back from yield"); */
337 }
338 }
339
340 if (lthreads[*ret].state == STATE_TERMINATED) {
341 i = *ret;
342 *ret = lthreads[*ret].retval;
343 lthreads[*ret].state = STATE_EMPTY;
344 PDEBUG ("thread_join: returing %d for tid %d", *ret, i);
345 return RC_SUCCESS;
346 }
347
348 PDEBUG ("thread_join: thread %d is not terminated!", *ret);
349 return RC_FAILURE;
350 }
351