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* SPDX-License-Identifier: GPL-2.0+
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* Author: Arun Dharankar <ADharankar@ATTBI.Com>
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* A very simple thread/schedular model:
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* - only one master thread, and no parent child relation maintained
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* - parent thread cannot be stopped or deleted
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* - no permissions or credentials
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* - no elaborate safety checks
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* - cooperative multi threading
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* - Simple round-robin scheduleing with no priorities
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* - no metering/statistics collection
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* Basic idea of implementing this is to allow more than one tests to
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* execute "simultaneously".
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* This may be modified such thread_yield may be called in syscalls, and
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#define STK_SIZE 8*1024
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#define STATE_RUNNABLE 1
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#define STATE_STOPPED 2
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#define STATE_TERMINATED 2
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#define MASTER_THREAD 0
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#define RC_FAILURE (-1)
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#define RC_SUCCESS (0)
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typedef vu_char *jmp_ctx;
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unsigned long setctxsp (vu_char *sp);
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int ppc_setjmp(jmp_ctx env);
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void ppc_longjmp(jmp_ctx env, int val);
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#define setjmp ppc_setjmp
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#define longjmp ppc_longjmp
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uchar context[CTX_SIZE];
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static volatile struct lthread lthreads[MAX_THREADS];
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static volatile int current_tid = MASTER_THREAD;
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#define PDEBUG(fmt, args...) { \
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printf("[%s %d %s]: ",__FILE__,__LINE__,__FUNCTION__);\
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printf(fmt, ##args); \
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static int testthread (void *);
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static void sched_init (void);
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static int thread_create (int (*func) (void *), void *arg);
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static int thread_start (int id);
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static void thread_yield (void);
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static int thread_delete (int id);
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static int thread_join (int *ret);
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#if 0 /* not used yet */
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static int thread_stop (int id);
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#endif /* not used yet */
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/* An example of schedular test */
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int sched (int ac, char *av[])
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int names[NUMTHREADS];
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for (i = 0; i < NUMTHREADS; i++) {
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j = thread_create (testthread, (void *) &names[i]);
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printf ("schedtest: Failed to create thread %d\n", i);
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printf ("schedtest: Created thread with id %d, name %d\n",
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printf ("schedtest: Threads created\n");
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printf ("sched_test: function=0x%08x\n", (unsigned)testthread);
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for (i = 0; i < NUMTHREADS; i++) {
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printf ("schedtest: Setting thread %d runnable\n", tid[i]);
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thread_start (tid[i]);
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printf ("schedtest: Started %d threads\n", NUMTHREADS);
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printf ("schedtest: Waiting for threads to complete\n");
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if (tstc () && getc () == 0x3) {
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printf ("schedtest: Aborting threads...\n");
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for (i = 0; i < NUMTHREADS; i++) {
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printf ("schedtest: Deleting thread %d\n", tid[i]);
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thread_delete (tid[i]);
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i = thread_join (&j);
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if (i == RC_FAILURE) {
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printf ("schedtest: No threads pending, "
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"exiting schedular test\n");
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printf ("schedtest: thread is %d returned %d\n", i, j);
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static int testthread (void *name)
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printf ("testthread: Begin executing thread, myname %d, &i=0x%08x\n",
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*(int *) name, (unsigned)&i);
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printf ("Thread %02d, i=%d\n", *(int *) name, i);
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for (i = 0; i < 0xffff * (*(int *) name + 1); i++) {
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if (tstc () && getc () == 0x3) {
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printf ("testthread: myname %d terminating.\n",
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return *(int *) name + 1;
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printf ("testthread: returning %d, i=0x%x\n",
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*(int *) name + 1, i);
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return *(int *) name + 1;
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static void sched_init (void)
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for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++)
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lthreads[i].state = STATE_EMPTY;
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current_tid = MASTER_THREAD;
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lthreads[current_tid].state = STATE_RUNNABLE;
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PDEBUG ("sched_init: master context = 0x%08x",
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(unsigned)lthreads[current_tid].context);
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static void thread_yield (void)
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PDEBUG ("thread_yield: current tid=%d", current_tid);
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#define SWITCH(new) \
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if(lthreads[new].state == STATE_RUNNABLE) { \
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PDEBUG("thread_yield: %d match, ctx=0x%08x", \
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(unsigned)lthreads[current_tid].context); \
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if(setjmp(lthreads[current_tid].context) == 0) { \
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PDEBUG("thread_yield: tid %d returns 0", \
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longjmp(lthreads[new].context, 1); \
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PDEBUG("thread_yield: tid %d returns 1", \
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for (i = current_tid + 1; i < MAX_THREADS; i++) {
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if (current_tid != 0) {
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for (i = 0; i <= current_tid; i++) {
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PDEBUG ("thread_yield: returning from thread_yield");
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static int thread_create (int (*func) (void *), void *arg)
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for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
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if (lthreads[i].state == STATE_EMPTY) {
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lthreads[i].state = STATE_STOPPED;
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lthreads[i].func = func;
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lthreads[i].arg = arg;
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PDEBUG ("thread_create: returns new tid %d", i);
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PDEBUG ("thread_create: returns failure");
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static int thread_delete (int id)
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if (id <= MASTER_THREAD || id > MAX_THREADS)
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if (current_tid == id)
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lthreads[id].state = STATE_EMPTY;
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static void thread_launcher (void)
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PDEBUG ("thread_launcher: invoking func=0x%08x",
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(unsigned)lthreads[current_tid].func);
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lthreads[current_tid].retval =
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lthreads[current_tid].func (lthreads[current_tid].arg);
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PDEBUG ("thread_launcher: tid %d terminated", current_tid);
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lthreads[current_tid].state = STATE_TERMINATED;
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printf ("thread_launcher: should NEVER get here!\n");
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static int thread_start (int id)
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PDEBUG ("thread_start: id=%d", id);
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if (id <= MASTER_THREAD || id > MAX_THREADS) {
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if (lthreads[id].state != STATE_STOPPED)
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if (setjmp (lthreads[current_tid].context) == 0) {
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lthreads[id].state = STATE_RUNNABLE;
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PDEBUG ("thread_start: to be stack=0%08x",
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(unsigned)lthreads[id].stack);
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setctxsp ((vu_char *)<hreads[id].stack[STK_SIZE]);
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PDEBUG ("thread_start: Thread id=%d started, parent returns", id);
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#if 0 /* not used so far */
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static int thread_stop (int id)
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if (id <= MASTER_THREAD || id >= MAX_THREADS)
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if (current_tid == id)
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lthreads[id].state = STATE_STOPPED;
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#endif /* not used so far */
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static int thread_join (int *ret)
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PDEBUG ("thread_join: *ret = %d", *ret);
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if (!(*ret == -1 || *ret > MASTER_THREAD || *ret < MAX_THREADS)) {
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PDEBUG ("thread_join: invalid tid %d", *ret);
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PDEBUG ("Checking for tid = -1");
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/* PDEBUG("thread_join: start while-loopn"); */
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for (i = MASTER_THREAD + 1; i < MAX_THREADS; i++) {
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if (lthreads[i].state == STATE_TERMINATED) {
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*ret = lthreads[i].retval;
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lthreads[i].state = STATE_EMPTY;
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/* PDEBUG("thread_join: returning retval %d of tid %d",
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if (lthreads[i].state != STATE_EMPTY) {
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PDEBUG ("thread_join: %d used slots tid %d state=%d",
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j, i, lthreads[i].state);
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PDEBUG ("thread_join: all slots empty!");
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/* PDEBUG("thread_join: yielding"); */
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/* PDEBUG("thread_join: back from yield"); */
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if (lthreads[*ret].state == STATE_TERMINATED) {
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*ret = lthreads[*ret].retval;
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lthreads[*ret].state = STATE_EMPTY;
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PDEBUG ("thread_join: returing %d for tid %d", *ret, i);
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PDEBUG ("thread_join: thread %d is not terminated!", *ret);