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[fixes#2] Adding a simple TCB and a new variable 'next_task' #4

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[fixes#2] Adding a simple TCB and a new variable 'next_task' #4

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1ad64c6
Add variable 'next_task'
fongwh1 Apr 24, 2015
8f09fbd
Add a simple task_control_block
fongwh1 Apr 24, 2015
c1b82cd
Change the way defining a struct
fongwh1 Apr 25, 2015
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19 changes: 13 additions & 6 deletions 06-Preemptive/os.c
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,11 @@ void delay(int count)
while (count--);
}

typedef struct {
unsigned int stack[STACK_SIZE];
unsigned int * usertask;
} tcb;

/* Exception return behavior */
#define HANDLER_MSP 0xFFFFFFF1
#define THREAD_MSP 0xFFFFFFF9
Expand Down Expand Up @@ -105,19 +110,19 @@ void task2_func(void)

int main(void)
{
unsigned int user_stacks[TASK_LIMIT][STACK_SIZE];
unsigned int *usertasks[TASK_LIMIT];
tcb user_proc[TASK_LIMIT];
size_t task_count = 0;
size_t current_task;
size_t next_task;

usart_init();

print_str("OS: Starting...\n");
print_str("OS: First create task 1\n");
usertasks[0] = create_task(user_stacks[0], &task1_func);
user_proc[0].usertask = create_task(user_proc[0].stack, &task1_func);
task_count += 1;
print_str("OS: Back to OS, create task 2\n");
usertasks[1] = create_task(user_stacks[1], &task2_func);
user_proc[1].usertask = create_task(user_proc[1].stack, &task2_func);
task_count += 1;

print_str("\nOS: Start round-robin scheduler!\n");
Expand All @@ -127,13 +132,15 @@ int main(void)
*SYSTICK_VAL = 0;
*SYSTICK_CTRL = 0x07;
current_task = 0;
next_task = current_task == (task_count - 1) ? 0 : current_task + 1;

while (1) {
print_str("OS: Activate next task\n");
usertasks[current_task] = activate(usertasks[current_task]);
user_proc[current_task].usertask = activate(user_proc[current_task].usertask);
print_str("OS: Back to OS\n");

current_task = current_task == (task_count - 1) ? 0 : current_task + 1;
current_task = next_task;
next_task = current_task == (task_count - 1) ? 0 : current_task + 1;
}

return 0;
Expand Down