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https://github.com/plctlab/riscv-operating-system-mooc.git
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a94fb0cd58
Following the standard RISC-V calling convention, make sure the stack pointer sp is always 16-byte aligned. Fixed an issue, make sure the sp of task point to the bottom of the stack, while originally we waste one byte (forgive my stupid ~~~). Signed-off-by: Wang Chen <wangchen20@iscas.ac.cn>
86 lines
1.6 KiB
C
86 lines
1.6 KiB
C
#include "os.h"
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/* defined in entry.S */
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extern void switch_to(struct context *next);
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#define MAX_TASKS 10
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#define STACK_SIZE 1024
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/*
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* In the standard RISC-V calling convention, the stack pointer sp
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* is always 16-byte aligned.
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*/
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uint8_t __attribute__((aligned(16))) task_stack[MAX_TASKS][STACK_SIZE];
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struct context ctx_tasks[MAX_TASKS];
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/*
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* _top is used to mark the max available position of ctx_tasks
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* _current is used to point to the context of current task
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*/
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static int _top = 0;
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static int _current = -1;
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void sched_init()
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{
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w_mscratch(0);
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/* enable machine-mode software interrupts. */
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w_mie(r_mie() | MIE_MSIE);
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}
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/*
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* implment a simple cycle FIFO schedular
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*/
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void schedule()
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{
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if (_top <= 0) {
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panic("Num of task should be greater than zero!");
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return;
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}
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_current = (_current + 1) % _top;
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struct context *next = &(ctx_tasks[_current]);
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switch_to(next);
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}
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/*
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* DESCRIPTION
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* Create a task.
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* - start_routin: task routine entry
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* RETURN VALUE
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* 0: success
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* -1: if error occured
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*/
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int task_create(void (*start_routin)(void))
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{
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if (_top < MAX_TASKS) {
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ctx_tasks[_top].sp = (reg_t) &task_stack[_top][STACK_SIZE];
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ctx_tasks[_top].pc = (reg_t) start_routin;
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_top++;
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return 0;
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} else {
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return -1;
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}
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}
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/*
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* DESCRIPTION
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* task_yield() causes the calling task to relinquish the CPU and a new
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* task gets to run.
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*/
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void task_yield()
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{
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/* trigger a machine-level software interrupt */
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int id = r_mhartid();
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*(uint32_t*)CLINT_MSIP(id) = 1;
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}
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/*
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* a very rough implementaion, just to consume the cpu
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*/
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void task_delay(volatile int count)
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{
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count *= 50000;
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while (count--);
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}
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