代码适用于X86_64架构。
不支持抢占，任务只能自己让出CPU。
下面是代码，将代码全部复制到一个.c文件中，即可编译运行。
/** 本软件为免费、开源软件。* 本软件的版权(包括源码及二进制发布版本)归一切公众所有。* 您可以自由使用、传播本软件。* 您也可以以任何形式、任何目的使用本软件(包括源码及二进制发布版本)，而不受任何版权限制。* =====================* 作者: 孙明保* 邮箱: sunmingbao@126.com*/#include <stdio.h>#include <string.h>#define MAX_TASK_NUM (10)#define TASK_STACK_SIZE (4096)#define DBG_PRINT(fmt, args…) \ do \ { \ printf("DBG:%s(%d)-%s:\n"fmt"\n", __FILE__,__LINE__,__FUNCTION__,##args); \ } while (0)typedef void * (*task_entry_ptr) (void *);typedef struct{ char name[64]; unsigned long state; task_entry_ptr entry; unsigned long ret; unsigned long sp; unsigned long pc; unsigned long stack[TASK_STACK_SIZE/sizeof(unsigned long)];} __attribute__((packed)) t_task;#define STATE_INVALID (0)#define STATE_SLEEPING (1)#define STATE_RUNNING (2)#define STATE_FINISHED (3)t_task g_at_tasks[MAX_TASK_NUM];int g_task_cnt = 0;unsigned long process_main_thread_sp;t_task *pt_cur_running_task;unsigned long prev_task_sp, prev_task_pc;unsigned long next_task_sp, next_task_pc;#define save_main_thread_context()\do {\asm volatile("pushfq\n\t"/* save flags */\ "pushq %%rax\n\t" \ "pushq %%rdi\n\t" \ "pushq %%rsi\n\t" \ "pushq %%rdx\n\t" \ "pushq %%rcx\n\t" \ "pushq %%rbx\n\t" \ "pushq %%rbp\n\t" \ "movq %%rsp,%[main_thread_sp]\n\t" \ : [main_thread_sp] "=m" (process_main_thread_sp)\ ); \} while (0)#define restore_main_thread_context()\do {\asm volatile("movq %[main_thread_sp],%%rsp\n\t" \ "popq %%rbp\n\t" \ "popq %%rbx\n\t" \ "popq %%rcx\n\t" \ "popq %%rdx\n\t" \ "popq %%rsi\n\t" \ "popq %%rdi\n\t" \ "popq %%rax\n\t" \ "popfq\n\t" \ :: [main_thread_sp] "m" (process_main_thread_sp)\ ); \} while (0)int i;int task_scheduler(){ unsigned long ret; asm volatile("movq %%rax,%[task_ret]\n\t" : [task_ret] "=m" (ret) ); if (pt_cur_running_task) { pt_cur_running_task->state=STATE_FINISHED; pt_cur_running_task->ret=ret; DBG_PRINT("task %s exit with code %lu", pt_cur_running_task->name, pt_cur_running_task->ret); } restore_main_thread_context(); for (i=0;i<MAX_TASK_NUM;i++) { pt_cur_running_task = &(g_at_tasks[i]); if (pt_cur_running_task->state==STATE_SLEEPING) { pt_cur_running_task->state=STATE_RUNNING; next_task_sp = pt_cur_running_task->sp; next_task_pc = pt_cur_running_task->pc; /* 准备运行下一个可运行任务 */ save_main_thread_context(); asm volatile("movq %[next_sp],%%rsp\n\t" /* "movq $0x0,%%rdi\n\t" "pushq task_return\n\t" */ "popq %%rbp\n\t" \ "popq %%rbx\n\t" \ "popq %%rcx\n\t" \ "popq %%rdx\n\t" \ "popq %%rsi\n\t" \ "popq %%rdi\n\t" \ "popq %%rax\n\t" \ "popfq\n\t" \ "jmp *%[next_pc]\n\t" :: [next_sp] "m" (next_task_sp), [next_pc] "m" (next_task_pc) ); } } DBG_PRINT("==no task to run. so we exit"); return 0;}#define push_task_stack(sp, data) \ do \{ \ sp–; \ *sp = data; \} while (0)int create_task(const char *name, void *task_entry, void *para){ unsigned long *sp; t_task *pt_task = &(g_at_tasks[g_task_cnt]); strncpy(pt_task->name, name, sizeof(pt_task->name)); pt_task->entry = task_entry; pt_task->sp = (unsigned long)((void *)(pt_task + 1)); pt_task->state = STATE_SLEEPING; sp = (void *)(pt_task->sp); push_task_stack(sp, (unsigned long)(void *)&task_scheduler); pt_task->pc = (unsigned long)task_entry; push_task_stack(sp, 0); push_task_stack(sp, 0); push_task_stack(sp, (unsigned long)para); push_task_stack(sp, 0); push_task_stack(sp, 0); push_task_stack(sp, 0); push_task_stack(sp, 0); push_task_stack(sp, pt_task->sp); /* push bp at last */ pt_task->sp = (unsigned long)(void *)sp; g_task_cnt++; return 0;}#define switch_to(prev, next)\do {\asm volatile("pushfq\n\t" \ "pushq %%rax\n\t" \ "pushq %%rdi\n\t" \ "pushq %%rsi\n\t" \ "pushq %%rdx\n\t" \ "pushq %%rcx\n\t" \ "pushq %%rbx\n\t" \ "pushq %%rbp\n\t" \ "movq %%rsp,%[prev_sp]\n\t" \ "movq $1f,%[prev_pc]\n\t" \ "movq %[next_sp],%%rsp\n\t" \ "popq %%rbp\n\t"/* restore EBP */\ "popq %%rbx\n\t" \ "popq %%rcx\n\t" \ "popq %%rdx\n\t" \ "popq %%rsi\n\t" \ "popq %%rdi\n\t" \ "popq %%rax\n\t" \ "popfq\n\t" \ "jmp *%[next_pc]\n\t" \ "1:\t"\ "nop\n\t" \ : [prev_sp] "=m" (prev->sp),\ [prev_pc] "=m" (prev->pc)\ : [next_sp] "m" (next_task_sp), [next_pc] "m" (next_task_pc) \);\}while (0)void schedule(){ t_task *prev=pt_cur_running_task, *next=NULL; for (i=0;i<MAX_TASK_NUM;i++) { next = &(g_at_tasks[i]); if (next->state==STATE_SLEEPING) { pt_cur_running_task->state=STATE_SLEEPING; prev_task_sp = pt_cur_running_task->sp; prev_task_pc = pt_cur_running_task->pc; pt_cur_running_task = next; pt_cur_running_task->state=STATE_RUNNING; next_task_sp = pt_cur_running_task->sp; next_task_pc = pt_cur_running_task->pc; break; } } if (i==MAX_TASK_NUM) return; switch_to(prev, next);}int start_sched(){ /* 准备运行初始任务 father_of_all_task — g_at_tasks[0] */ save_main_thread_context(); task_scheduler(); return 0;}
天才就是这样，终身努力，便是天才。
