feat(ex_13_1): update task create & add os_schedule

code/exercises/ex_13_1/Makefile

@@ -44,7 +44,7 @@ debug: all
 	@echo "Press Ctrl-C and then input 'quit' to exit GDB and QEMU"
 	@echo "-------------------------------------------------------"
 	@${QEMU} ${QFLAGS} -kernel os.elf -s -S &
-	@${GDB} os.elf -q -x ../gdbinit
+	@${GDB} os.elf -q -x ./gdbinit
 
 .PHONY : code
 code: all

code/exercises/ex_13_1/gdbinit

@@ -0,0 +1,23 @@
+display/z $mscratch
+display/z $mepc
+display/z $mie
+display/z $mstatus
+display/z $mcause
+display/z $a0
+display/z $a1
+display/z $pc
+display/z $t5
+display/z $t6
+
+set disassemble-next-line on
+
+b _start
+b sched_init
+b os_main
+b trap_vector
+b trap_handler
+b schedule
+b switch_to
+
+target remote : 1234
+c

code/exercises/ex_13_1/kernel.c

@@ -13,6 +13,17 @@ extern void trap_init(void);
 extern void plic_init(void);
 extern void timer_init(void);
 
+void os_schedule(void) {
+	// 内核调度
+	while (1) {
+		uart_puts("os_schedule: Activate next task\n");
+		int id = r_mhartid();
+		*(uint32_t*)CLINT_MSIP(id) = 1;
+		uart_puts("os_schedule: Back to OS\n");
+		task_delay(10000);
+	}
+}
+
 void start_kernel(void)
 {
 	uart_init();

code/exercises/ex_13_1/os.h

@@ -61,9 +61,11 @@ struct context {
 	reg_t pc; // offset: 31 *4 = 124
 };
 
-extern int  task_create(void (*task)(void));
+extern int  task_create(void (*task)(void* param), void* param, uint8_t priority, uint32_t timeslice);
 extern void task_delay(volatile int count);
 extern void task_yield();
+extern void task_exit();
+extern void back_to_os();
 
 /* plic */
 extern int plic_claim(void);

code/exercises/ex_13_1/riscv.h

@@ -69,6 +69,13 @@ static inline void w_mscratch(reg_t x)
 	asm volatile("csrw mscratch, %0" : : "r" (x));
 }
 
+static inline reg_t r_mscratch()
+{
+	reg_t x;
+	asm volatile("csrr %0, mscratch" : "=r" (x));
+	return x;
+}
+
 /* Machine-mode interrupt vector */
 static inline void w_mtvec(reg_t x)
 {

code/exercises/ex_13_1/sched.c

@@ -12,33 +12,88 @@ extern void switch_to(struct context *next);
 uint8_t __attribute__((aligned(16))) task_stack[MAX_TASKS][STACK_SIZE];
 struct context ctx_tasks[MAX_TASKS];
 
+uint8_t __attribute__((aligned(16))) stack_os[STACK_SIZE];
+struct context ctx_os;
+
+uint8_t task_priorities[MAX_TASKS];
+uint8_t task_status[MAX_TASKS];
+
+#define TASK_EMPTY 0
+#define TASK_READY 1
+#define TASK_RUNNING 2
+#define TASK_BLOCKED 3
+#define TASK_EXITED 4
+
+#define task_schedulable(i) (task_status[i] == TASK_READY || task_status[i] == TASK_RUNNING)
+
+uint32_t task_timeslice[MAX_TASKS];
+
 /*
- * _top is used to mark the max available position of ctx_tasks
  * _current is used to point to the context of current task
  */
-static int _top = 0;
 static int _current = -1;
 
+extern void os_schedule();
+
 void sched_init()
 {
-	w_mscratch(0);
+	/* init ctx_os */
+	ctx_os.sp = (reg_t) &stack_os[STACK_SIZE];
+	ctx_os.pc = (reg_t) os_schedule;
+
+	w_mscratch((reg_t)&ctx_os);
 
 	/* enable machine-mode software interrupts. */
 	w_mie(r_mie() | MIE_MSIE);
+
+	// init task status & priority
+	for (int i = 0; i < MAX_TASKS; i++) {
+		task_status[i] = TASK_EMPTY;
+		task_priorities[i] = 0xff;
+		task_timeslice[i] = 0;
+	}
 }
 
 /*
  * implment a simple cycle FIFO schedular
  */
 void schedule()
 {
-	if (_top <= 0) {
-		panic("Num of task should be greater than zero!");
-		return;
+	// 先扫描获取最高优先级
+	int highest_priority = 0xff;
+	for (int i = 0; i < MAX_TASKS; i++) {
+		if (task_schedulable(i) && task_priorities[i] < highest_priority) {
+			highest_priority = task_priorities[i];
+		}
 	}
-
-	_current = (_current + 1) % _top;
+	// 扫描获取最高优先级的任务
+	int next_task_id = -1;
+	for (int i = 0; i < MAX_TASKS; i++) {
+		if (task_schedulable(i) && task_priorities[i] == highest_priority) {
+			if (i > _current) {
+				next_task_id = i;
+				break;
+			}
+		}
+	}
+	// 如果没有找到，从头开始找
+	if (next_task_id == -1) {
+		for (int i = 0; i < MAX_TASKS; i++) {
+			if (task_schedulable(i) && task_priorities[i] == highest_priority) {
+				next_task_id = i;
+				break;
+			}
+		}
+	}
+	if (next_task_id == -1) {
+		// 没有可调度的任务
+		printf("no schedulable task!\n");
+		switch_to(&ctx_os);
+	}
+	// 切换到下一个任务
+	_current = next_task_id;
 	struct context *next = &(ctx_tasks[_current]);
+	task_status[_current] = TASK_RUNNING;
 	switch_to(next);
 }
 
@@ -50,16 +105,28 @@ void schedule()
  * 	0: success
  * 	-1: if error occured
  */
-int task_create(void (*start_routin)(void))
+int task_create(void (*start_routin)(void* param), void* param,
+								uint8_t priority, uint32_t timeslice)
 {
-	if (_top < MAX_TASKS) {
-		ctx_tasks[_top].sp = (reg_t) &task_stack[_top][STACK_SIZE];
-		ctx_tasks[_top].pc = (reg_t) start_routin;
-		_top++;
-		return 0;
-	} else {
+	int task_id = -1;
+	for (int i = 0; i < MAX_TASKS; i++) {
+		if (task_status[i] == TASK_EMPTY || task_status[i] == TASK_EXITED) {
+			task_id = i;
+			break;
+		}
+	}
+	if (task_id == -1) {
 		return -1;
 	}
+	task_status[task_id] = TASK_READY;
+	task_priorities[task_id] = priority;
+	task_timeslice[task_id] = timeslice;
+	// init stack
+	ctx_tasks[task_id].sp = (reg_t) &task_stack[task_id][STACK_SIZE];
+	ctx_tasks[task_id].pc = (reg_t) start_routin;
+	// init context
+	ctx_tasks[task_id].a0 = (reg_t) param;
+	return 0;
 }
 
 /*
@@ -69,6 +136,19 @@ int task_create(void (*start_routin)(void))
  */
 void task_yield()
 {
+	task_status[_current] = TASK_READY;
+	/* trigger a machine-level software interrupt */
+	int id = r_mhartid();
+	*(uint32_t*)CLINT_MSIP(id) = 1;
+}
+
+/*
+ * DESCRIPTION
+ * 	task_exit() causes the calling task to exit.
+ */
+void task_exit()
+{
+	task_status[_current] = TASK_EXITED;
 	/* trigger a machine-level software interrupt */
 	int id = r_mhartid();
 	*(uint32_t*)CLINT_MSIP(id) = 1;

code/exercises/ex_13_1/timer.c

@@ -4,6 +4,7 @@ extern void schedule(void);
 
 /* interval ~= 1s */
 #define TIMER_INTERVAL CLINT_TIMEBASE_FREQ
+#define TIMER_INTERVAL_MS (TIMER_INTERVAL / 1000)
 
 static uint32_t _tick = 0;
 
@@ -22,7 +23,7 @@ void timer_init()
 	 * On reset, mtime is cleared to zero, but the mtimecmp registers 
 	 * are not reset. So we have to init the mtimecmp manually.
 	 */
-	timer_load(TIMER_INTERVAL);
+	timer_load(TIMER_INTERVAL_MS * 500);
 
 	/* enable machine-mode timer interrupts. */
 	w_mie(r_mie() | MIE_MTIE);
@@ -33,7 +34,7 @@ void timer_handler()
 	_tick++;
 	printf("tick: %d\n", _tick);
 
-	timer_load(TIMER_INTERVAL);
+	timer_load(TIMER_INTERVAL_MS * 1000);
 
 	schedule();
 }

code/exercises/ex_13_1/trap.c

@@ -40,10 +40,10 @@ reg_t trap_handler(reg_t epc, reg_t cause)
 			uart_puts("software interruption!\n");
 			/*
 			 * acknowledge the software interrupt by clearing
-    			 * the MSIP bit in mip.
+			 * the MSIP bit in mip.
 			 */
 			int id = r_mhartid();
-    			*(uint32_t*)CLINT_MSIP(id) = 0;
+			*(uint32_t*)CLINT_MSIP(id) = 0;
 
 			schedule();
 

code/exercises/ex_13_1/user.c

@@ -2,7 +2,7 @@
 
 #define DELAY 1000
 
-void user_task0(void)
+void user_task0(void* param)
 {
 	uart_puts("Task 0: Created!\n");
 
@@ -14,7 +14,7 @@ void user_task0(void)
 	}
 }
 
-void user_task1(void)
+void user_task1(void* param)
 {
 	uart_puts("Task 1: Created!\n");
 	while (1) {
@@ -23,10 +23,34 @@ void user_task1(void)
 	}
 }
 
+void user_task(void* param)
+{
+	int id = (int) param;
+	printf("Task %d: Created!\n", id);
+	int iter_cnt = id / 1000 + 5;
+	while (1) {
+		printf("Task %d: Running...\n", id);
+		task_delay(DELAY);
+		if (iter_cnt-- == 0) {
+			break;
+		}
+	}
+	printf("Task %d: Finished!\n", id);
+	task_exit();
+}
+
 /* NOTICE: DON'T LOOP INFINITELY IN main() */
 void os_main(void)
 {
-	task_create(user_task0);
-	task_create(user_task1);
+	// task_create(user_task0, NULL, 255, 0);
+	// task_create(user_task1, NULL, 255, 0);
+	task_create(user_task, (void *)3000, 0, 0);
+	task_create(user_task, (void *)8003, 3, 0);
+	task_create(user_task, (void *)2005, 5, 0);
+	task_create(user_task, (void *)5000, 0, 0);
+	task_create(user_task, (void *)9004, 4, 0);
+	task_create(user_task, (void *)6001, 1, 0);
+	task_create(user_task, (void *)7002, 2, 0);
+	task_create(user_task, (void *)4000, 0, 0);
 }