aboutsummaryrefslogtreecommitdiff
path: root/src/sys/schedule.c
blob: b06896327eeda84723d81facd22a3cf9c36ad5fa (plain)
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
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
#include <cpu.h>
#include <globals.h>
#include <graphics/lfb.h>
#include <drivers/uart.h>
#include <lib/kmem.h>
#include <sys/schedule.h>
#include <util/mutex.h>

extern void kernel_usr_task_loop(void);

void init_scheduler(void)
{
	// Set rthread to usrloopthread - an infinitely running thread so that the pointer will never be null
	usrloopthread.pc = (void*)kernel_usr_task_loop;
	usrloopthread.sp = (void*)0x5FC8;
	*(unsigned long**)usrloopthread.sp = (unsigned long*)kernel_usr_task_loop;
	usrloopthread.sp_base = -1;
	usrloopthread.mptr = 0;
	usrloopthread.pid = -1;
	usrloopthread.priority = -1;
	usrloopthread.old_priority = -1;
	usrloopthread.status = THREAD_READY;
	scheduler.rthread = &usrloopthread;
	// Initialize Rotating Buffers
	struct ThreadQueues* tq;
	for (int i = 0; i < PRIORITIES; i++) {
		tq = &scheduler.thread_queues[i];
		struct ThreadRotBuffer* trb = &tq->ready;
		for (int i = 0; i < TQUEUE_CNT; i++) {
			trb->roffset = 0;
			trb->woffset = 0;
			for (int j = 0; j < TQUEUE_MAX; j++)
				trb->queue[j] = 0;
			trb += 1;
		}
	}
	sched_stack_count = 0;
	// Initialize nextpid
	nextpid = FIRST_AVAIL_PID;
}

struct RStack get_stack(void)
{
	struct RStack r = {.sp = 0, .idx = -1};
	// Find an available stack
	for (int i = 0; i < MAX_THREADS; i++) {
		if (stacks_table[i] == 0) {
			// Mark unavailable
			stacks_table[i] = 1;
			r.idx = i;
			r.sp = (void*)0x20000000 - STACK_SIZE*i;
			return r;
		}
	}
	return r;
}

void add_thread(void* pc, void* arg, unsigned char priority)
{
	//void* sp = get_stack();
	struct RStack r = get_stack();
	//struct Thread* thread = (struct Thread*)malloca(sizeof(struct Thread), 4);
	struct Thread* thread = (struct Thread*)kmalloc(sizeof(struct Thread));
	thread->pc = pc;
	// Valid stack has been obtained for this thread
	if (r.sp) {
		thread->sp_base = r.idx;
		unsigned long* argp = r.sp;
		argp -= 13;
		*argp = (unsigned long)arg; // Set r0 to the argument
		argp -= 1;
		*(unsigned long**)argp = (unsigned long*)cleanup; // Set lr to the cleanup function
		thread->sp = (void*)argp;
		thread->status = THREAD_READY;
		sched_stack_count++;
	}
	// Couldn't allocate a proper stack
	else {
		thread->sp_base = r.idx;
		thread->sp = r.sp;
		thread->status = THREAD_SERROR;
	}
	thread->mptr = (void*)0;
	thread->pid = nextpid++;
	// Reset next pid on overflow
	if (nextpid < FIRST_AVAIL_PID) {
		nextpid = FIRST_AVAIL_PID;
	}
	thread->priority = priority % PRIORITIES;
	thread->old_priority = -1;
	thread->preempt = 0;
	// Add Thread* to scheduler's appropriate buffer
	struct ThreadQueues* tq = &scheduler.thread_queues[thread->priority];
	struct ThreadRotBuffer* trb;
	// Add to stack error queue if stack was not obtained
	if (thread->status == THREAD_SERROR) {
		trb = &tq->serror;
	}
	else {
		trb = &tq->ready;
	}
	trb->queue[trb->woffset++] = thread;
	trb->woffset %= TQUEUE_MAX;
	// Schedule if this was called in usermode
	unsigned long mode = getmode() & 0x1F;
	if (mode == 0x10) {
		sys0(SYS_YIELD_HIGH);
	}
}

void uart_scheduler(void)
{
	uart_string("Scheduler Info\n==============\nCurrent\n");
	uart_hex((unsigned long)scheduler.rthread);
	uart_char(' ');
	kmemshow32((void*)scheduler.rthread, 7);
	struct ThreadQueues* tq;
	for(int p = 0; p < PRIORITIES; p++) {
		uart_string("Priority ");
		uart_10(p);
		uart_char('\n');
		tq = &scheduler.thread_queues[p];
		struct ThreadRotBuffer* trb;
		trb = &tq->ready;
		for(int i = 0; i < TQUEUE_CNT; i++) {
			if (trb->roffset == trb->woffset) {
				trb += 1;
				continue;
			}
			uart_string("Queue ");
			uart_10(i);
			uart_char('\n');
			unsigned long roffset = trb->roffset;
			while (roffset != trb->woffset) {
				uart_hex((unsigned long)trb->queue[roffset]);
				uart_char(' ');
				kmemshow32((void*)trb->queue[roffset], 7);
				roffset++;
				roffset %= TQUEUE_MAX;
			}
			trb += 1;
		}
	}
	uart_string("==============\n");
}

struct Thread* next_thread(void)
{
	struct Thread* next = &usrloopthread;
	// Recurse through all priorities to try to find a ready thread
	for (int p = 0; p < PRIORITIES; p++) {
		struct ThreadRotBuffer* rb = &scheduler.thread_queues[p].ready;
		if (rb->roffset == rb->woffset)
			continue;
		return rb->queue[rb->roffset];
	}
	// No thread found, use basic usrloopthread while waiting for new thread
	return next;
}

void* get_rthread_roffset(void)
{
	return &scheduler.thread_queues[scheduler.rthread->priority].ready.roffset;
}

void yield(void)
{
	struct Thread* rthread = scheduler.rthread;
	// usrloopthread should not be yielded
	if (rthread == &usrloopthread)
		return;
	// Put current thread at the end of its ready queue,
	//  thus any threads of the same priority can be run first
	unsigned char priority = rthread->priority;
	struct ThreadRotBuffer* trb = &scheduler.thread_queues[priority].ready;
	trb->roffset += 1;
	trb->roffset %= TQUEUE_MAX;
	trb->queue[trb->woffset++] = rthread;
	trb->woffset %= TQUEUE_MAX;
}

void sched_mutex_yield(void* m)
{
	struct Thread* rthread = scheduler.rthread;
	// usrloopthread should not be yielded
	if (rthread == &usrloopthread)
		return;
	unsigned char priority = rthread->priority;
	// Signify which lock this thread is waiting for
	rthread->mptr = m;
	struct ThreadRotBuffer* trbb = &scheduler.thread_queues[priority].ready;
	struct ThreadRotBuffer* trbm = &scheduler.thread_queues[priority].mwait;
	// Move to next thread in the current thread priority's ready queue
	trbb->roffset += 1;
	trbb->roffset %= TQUEUE_MAX;
	// Add thread to waiting queue
	trbm->queue[trbm->woffset++] = rthread;
	trbm->woffset %= TQUEUE_MAX;
	// Find the thread with the mutex
	struct ThreadQueues* tq;
	// Search through each priority
	for (int i = 0; i < PRIORITIES; i++) {
		tq = &scheduler.thread_queues[i];
		struct ThreadRotBuffer* trb = &tq->ready;
		// Search through each queue at the current priority
		for (int i = 0; i < TQUEUE_CNT; i++) {
			unsigned long roffset = trb->roffset;
			unsigned long woffset = trb->woffset;
			// Search through the threads
			while(roffset != woffset) {
				// Found thread
				if (trb->queue[roffset]->pid == ((struct Mutex*)m)->pid) {
					// Promote the thread to the new priority
					if (trb->queue[roffset]->priority > priority) {
						trbb->queue[trbb->woffset++] = trb->queue[roffset];
						// Set the old priority if not set
						if(trb->queue[roffset]->old_priority == 0xFF)
							trb->queue[roffset]->old_priority = trb->queue[roffset]->priority;
						// Promote the priority
						trb->queue[roffset]->priority = priority;
						trbb->woffset %= TQUEUE_MAX;
						unsigned long coffset = roffset;
						// Fill gap where the thread was removed
						while (coffset != woffset) {
							trb->queue[coffset] = trb->queue[(coffset+1)%TQUEUE_MAX];
							coffset++;
							coffset %= TQUEUE_MAX;
						}
						// Move the woffset back since the gap was filled in
						if (trb->woffset == 0)
							trb->woffset = TQUEUE_MAX-1;
						else
							trb->woffset--;
					}
					return;
				}
				roffset++;
				roffset %= TQUEUE_MAX;
			}
			// Check next queue in given priority
			trb += 1;
		}
	}
}

void sched_mutex_resurrect(void* m)
{
	// Look through each priority
	for (int p = 0; p < PRIORITIES; p++) {
		struct ThreadRotBuffer* trbm = &scheduler.thread_queues[p].mwait;
		unsigned long roffset = trbm->roffset;
		// Look through the lock wait queue
		while (roffset != trbm->woffset) {
			// Check if the thread is waiting for the released mutex
			if (trbm->queue[roffset]->mptr == m) {
				// Ressurect the thread
				trbm->queue[roffset]->mptr = 0;
				struct ThreadRotBuffer* trb = &scheduler.thread_queues[trbm->queue[roffset]->priority].ready;
				trb->queue[trb->woffset++] = trbm->queue[roffset];
				trb->woffset %= TQUEUE_MAX;
				// Copy all next backward to fill space
				unsigned long coffset = roffset;
				while (coffset != trbm->woffset) {
					trbm->queue[coffset] = trbm->queue[(coffset+1)%TQUEUE_MAX];
					coffset++;
					coffset %= TQUEUE_MAX;
				}
				// Move the woffset back since the space was filled
				if(trbm->woffset == 0)
					trbm->woffset = TQUEUE_MAX-1;
				else
					trbm->woffset--;
				// Move the read pointer ahead
				struct Thread* rthread = scheduler.rthread;
				// Move the current thread to its old priority if it was promoted earlier
				if (rthread->old_priority != 0xFF) {
					struct ThreadRotBuffer* rtrb = &scheduler.thread_queues[rthread->priority].ready;
					struct ThreadRotBuffer* ntrb = &scheduler.thread_queues[rthread->old_priority].ready;
					rtrb->roffset++;
					rtrb->roffset %= TQUEUE_MAX;
					if (ntrb->roffset == 0)
						ntrb->roffset = TQUEUE_MAX-1;
					else
						ntrb->roffset--;
					ntrb->queue[ntrb->roffset] = rthread;
					rthread->priority = rthread->old_priority;
					rthread->old_priority = -1;
				}
				return;
			}
			roffset++;
			roffset %= TQUEUE_MAX;
		}
	}
}

// TODO: Check offsets