examples/sched.c

   1 /*
   2  * This program is free software; you can redistribute it and/or
   3  * modify it under the terms of the GNU General Public License as
   4  * published by the Free Software Foundation; either version 2 of
   5  * the License, or (at your option) any later version.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  15  * MA 02111-1307 USA
  16  */
  17
  18 #include <common.h>
  19 #include <exports.h>
  20
  21 /*
  22  * Author: Arun Dharankar <ADharankar@ATTBI.Com>
  23  *
  24  * A very simple thread/schedular model:
  25  *   - only one master thread, and no parent child relation maintained
  26  *   - parent thread cannot be stopped or deleted
  27  *   - no permissions or credentials
  28  *   - no elaborate safety checks
  29  *   - cooperative multi threading
  30  *   - Simple round-robin scheduleing with no priorities
  31  *   - no metering/statistics collection
  32  *
  33  * Basic idea of implementing this is to allow more than one tests to
  34  * execute "simultaneously".
  35  *
  36  * This may be modified such thread_yield may be called in syscalls, and
  37  * timer interrupts.
  38  */
  39
  40
  41 #define MAX_THREADS 8
  42
  43 #define CTX_SIZE 512
  44 #define STK_SIZE 8*1024
  45
  46 #define STATE_EMPTY 0
  47 #define STATE_RUNNABLE 1
  48 #define STATE_STOPPED 2
  49 #define STATE_TERMINATED 2
  50
  51 #define MASTER_THREAD 0
  52
  53 #define RC_FAILURE      (-1)
  54 #define RC_SUCCESS      (0)
  55
  56 typedef vu_char *jmp_ctx;
  57 unsigned long setctxsp (vu_char *sp);
  58 int ppc_setjmp(jmp_ctx env);
  59 void ppc_longjmp(jmp_ctx env, int val);
  60 #define setjmp  ppc_setjmp
  61 #define longjmp ppc_longjmp
  62
  63 struct lthread {
  64         int state;
  65         int retval;
  66         char stack[STK_SIZE];
  67         uchar context[CTX_SIZE];
  68         int (*func) (void *);
  69         void *arg;
  70 };
  71 static volatile struct lthread lthreads[MAX_THREADS];
  72 static volatile int current_tid = MASTER_THREAD;
  73
  74
  75 static uchar dbg = 0;
  76
  77 #define PDEBUG(fmt, args...)     {                                      \
  78         if(dbg != 0) {                                                  \
  79                 printf("[%s %d %s]: ",__FILE__,__LINE__,__FUNCTION__);\
  80                 printf(fmt, ##args);                            \
  81                 printf("\n");                                   \
  82         }                                                               \
  83 }
  84
  85 static int testthread (void *);
  86 static void sched_init (void);
  87 static int thread_create (int (*func) (void *), void *arg);
  88 static int thread_start (int id);
  89 static void thread_yield (void);
  90 static int thread_delete (int id);
  91 static int thread_join (int *ret);
  92
  93 #if 0                                                   /* not used yet */
  94 static int thread_stop (int id);
  95 #endif                                                  /* not used yet */
  96
  97 /* An example of schedular test */
  98
  99 #define NUMTHREADS 7
 100 int sched (int ac, char *av[])
 101 {
 102         int i, j;
 103         int tid[NUMTHREADS];
 104         int names[NUMTHREADS];
 105
 106         app_startup(av);
 107
 108         sched_init ();
 109
 110         for (i = 0; i < NUMTHREADS; i++) {
 111                 names[i] = i;
 112                 j = thread_create (testthread, (void *) &names[i]);
 113                 if (j == RC_FAILURE)
 114                         printf ("schedtest: Failed to create thread %d\n", i);
 115                 if (j > 0) {
 116                         printf ("schedtest: Created thread with id %d, name %d\n",
 117                                                 j, i);
 118                         tid[i] = j;
 119                 }
 120         }
 121         printf ("schedtest: Threads created\n");
 122
 123         printf ("sched_test: function=0x%08x\n", (unsigned)testthread);
 124         for (i = 0; i < NUMTHREADS; i++) {
 125                 printf ("schedtest: Setting thread %d runnable\n", tid[i]);
 126                 thread_start (tid[i]);
 127                 thread_yield ();
 128         }
 129         printf ("schedtest: Started %d threads\n", NUMTHREADS);
 130
 131         while (1) {
 132                 printf ("schedtest: Waiting for threads to complete\n");
 133                 if (tstc () && getc () == 0x3) {
 134                         printf ("schedtest: Aborting threads...\n");
 135                         for (i = 0; i < NUMTHREADS; i++) {
 136                                 printf ("schedtest: Deleting thread %d\n", tid[i]);
 137                                 thread_delete (tid[i]);
 138                         }
 139                         return RC_SUCCESS;
 140                 }
 141                 j = -1;
 142                 i = thread_join (&j);
 143                 if (i == RC_FAILURE) {
 144                         printf ("schedtest: No threads pending, "
 145                                                 "exiting schedular test\n");
 146                         return RC_SUCCESS;
 147                 }
 148                 printf ("schedtest: thread is %d returned %d\n", i, j);
 149                 thread_yield ();
 150         }
 151
 152         return RC_SUCCESS;
 153 }
 154
 155 static int testthread (void *name)
 156 {
 157         int i;
 158
 159         printf ("testthread: Begin executing thread, myname %d, &i=0x%08x\n",
 160                 *(int *) name, (unsigned)&i);
 161
 162         printf ("Thread %02d, i=%d\n", *(int *) name, i);
 163
 164         for (i = 0; i < 0xffff * (*(int *) name + 1); i++) {
 165                 if (tstc () && getc () == 0x3) {
 166                         printf ("testthread: myname %d terminating.\n",
 167                                                 *(int *) name);
 168                         return *(int *) name + 1;
 169                 }
 170
 171                 if (i % 100 == 0)
 172                         thread_yield ();
 173         }
 174
 175         printf ("testthread: returning %d, i=0x%x\n",
 176                                 *(int *) name + 1, i);
 177
 178         return *(int *) name + 1;
 179 }
 180
 181
 182 static void sched_init (void)
 183 {
 184         int i;
 185
 186         for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++)
 187                 lthreads[i].state = STATE_EMPTY;
 188
 189         current_tid = MASTER_THREAD;
 190         lthreads[current_tid].state = STATE_RUNNABLE;
 191         PDEBUG ("sched_init: master context = 0x%08x",
 192                 (unsigned)lthreads[current_tid].context);
 193         return;
 194 }
 195
 196 static void thread_yield (void)
 197 {
 198         static int i;
 199
 200         PDEBUG ("thread_yield: current tid=%d", current_tid);
 201
 202 #define SWITCH(new)                                                     \
 203         if(lthreads[new].state == STATE_RUNNABLE) {                     \
 204                 PDEBUG("thread_yield: %d match, ctx=0x%08x",            \
 205                         new,                                            \
 206                         (unsigned)lthreads[current_tid].context);       \
 207                 if(setjmp(lthreads[current_tid].context) == 0) {        \
 208                         current_tid = new;                              \
 209                         PDEBUG("thread_yield: tid %d returns 0",        \
 210                                 new);                                   \
 211                         longjmp(lthreads[new].context, 1);              \
 212                 } else {                                                \
 213                         PDEBUG("thread_yield: tid %d returns 1",        \
 214                                 new);                                   \
 215                         return;                                         \
 216                 }                                                       \
 217         }
 218
 219         for (i = current_tid + 1; i < MAX_THREADS; i++) {
 220                 SWITCH (i);
 221         }
 222
 223         if (current_tid != 0) {
 224                 for (i = 0; i <= current_tid; i++) {
 225                         SWITCH (i);
 226                 }
 227         }
 228
 229         PDEBUG ("thread_yield: returning from thread_yield");
 230         return;
 231 }
 232
 233 static int thread_create (int (*func) (void *), void *arg)
 234 {
 235         int i;
 236
 237         for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
 238                 if (lthreads[i].state == STATE_EMPTY) {
 239                         lthreads[i].state = STATE_STOPPED;
 240                         lthreads[i].func = func;
 241                         lthreads[i].arg = arg;
 242                         PDEBUG ("thread_create: returns new tid %d", i);
 243                         return i;
 244                 }
 245         }
 246
 247         PDEBUG ("thread_create: returns failure");
 248         return RC_FAILURE;
 249 }
 250
 251 static int thread_delete (int id)
 252 {
 253         if (id <= MASTER_THREAD || id > MAX_THREADS)
 254                 return RC_FAILURE;
 255
 256         if (current_tid == id)
 257                 return RC_FAILURE;
 258
 259         lthreads[id].state = STATE_EMPTY;
 260         return RC_SUCCESS;
 261 }
 262
 263 static void thread_launcher (void)
 264 {
 265         PDEBUG ("thread_launcher: invoking func=0x%08x",
 266                    (unsigned)lthreads[current_tid].func);
 267
 268         lthreads[current_tid].retval =
 269                         lthreads[current_tid].func (lthreads[current_tid].arg);
 270
 271         PDEBUG ("thread_launcher: tid %d terminated", current_tid);
 272
 273         lthreads[current_tid].state = STATE_TERMINATED;
 274         thread_yield ();
 275         printf ("thread_launcher: should NEVER get here!\n");
 276
 277         return;
 278 }
 279
 280 static int thread_start (int id)
 281 {
 282         PDEBUG ("thread_start: id=%d", id);
 283         if (id <= MASTER_THREAD || id > MAX_THREADS) {
 284                 return RC_FAILURE;
 285         }
 286
 287         if (lthreads[id].state != STATE_STOPPED)
 288                 return RC_FAILURE;
 289
 290         if (setjmp (lthreads[current_tid].context) == 0) {
 291                 lthreads[id].state = STATE_RUNNABLE;
 292                 current_tid = id;
 293                 PDEBUG ("thread_start: to be stack=0%08x",
 294                         (unsigned)lthreads[id].stack);
 295                 setctxsp ((vu_char *)&lthreads[id].stack[STK_SIZE]);
 296                 thread_launcher ();
 297         }
 298
 299         PDEBUG ("thread_start: Thread id=%d started, parent returns", id);
 300
 301         return RC_SUCCESS;
 302 }
 303
 304 #if 0   /* not used so far */
 305 static int thread_stop (int id)
 306 {
 307         if (id <= MASTER_THREAD || id >= MAX_THREADS)
 308                 return RC_FAILURE;
 309
 310         if (current_tid == id)
 311                 return RC_FAILURE;
 312
 313         lthreads[id].state = STATE_STOPPED;
 314         return RC_SUCCESS;
 315 }
 316 #endif  /* not used so far */
 317
 318 static int thread_join (int *ret)
 319 {
 320         int i, j = 0;
 321
 322         PDEBUG ("thread_join: *ret = %d", *ret);
 323
 324         if (!(*ret == -1 || *ret > MASTER_THREAD || *ret < MAX_THREADS)) {
 325                 PDEBUG ("thread_join: invalid tid %d", *ret);
 326                 return RC_FAILURE;
 327         }
 328
 329         if (*ret == -1) {
 330                 PDEBUG ("Checking for tid = -1");
 331                 while (1) {
 332                         /* PDEBUG("thread_join: start while-loopn"); */
 333                         j = 0;
 334                         for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
 335                                 if (lthreads[i].state == STATE_TERMINATED) {
 336                                         *ret = lthreads[i].retval;
 337                                         lthreads[i].state = STATE_EMPTY;
 338                                         /* PDEBUG("thread_join: returning retval %d of tid %d",
 339                                            ret, i); */
 340                                         return RC_SUCCESS;
 341                                 }
 342
 343                                 if (lthreads[i].state != STATE_EMPTY) {
 344                                         PDEBUG ("thread_join: %d used slots tid %d state=%d",
 345                                                    j, i, lthreads[i].state);
 346                                         j++;
 347                                 }
 348                         }
 349                         if (j == 0) {
 350                                 PDEBUG ("thread_join: all slots empty!");
 351                                 return RC_FAILURE;
 352                         }
 353                         /*  PDEBUG("thread_join: yielding"); */
 354                         thread_yield ();
 355                         /*  PDEBUG("thread_join: back from yield"); */
 356                 }
 357         }
 358
 359         if (lthreads[*ret].state == STATE_TERMINATED) {
 360                 i = *ret;
 361                 *ret = lthreads[*ret].retval;
 362                 lthreads[*ret].state = STATE_EMPTY;
 363                 PDEBUG ("thread_join: returing %d for tid %d", *ret, i);
 364                 return RC_SUCCESS;
 365         }
 366
 367         PDEBUG ("thread_join: thread %d is not terminated!", *ret);
 368         return RC_FAILURE;
 369 }