scheduler.c

#include <rtdef.h>
#include <rtconfig.h>
#include <rtservice.h>
#include <rthw.h>

/* 已知一个结构体里面的成员的地址，反推出该结构体的首地址 */
#define rt_container_of(ptr, type, member) \
    ((type *)((char *)(ptr) - (unsigned long)(&((type *)0)->member)))

#define rt_list_entry(node, type, member) \
    rt_container_of(node, type, member)

/* 线程控制块指针，用于指向当前线程 */
struct rt_thread *rt_current_thread;

/* 线程就绪列表 */
rt_list_t rt_thread_priority_table[RT_THREAD_PRIORITY_MAX];

/* 线程休眠列表 */
rt_list_t rt_thread_defunct;

/* 初始化系统调度器 */
void rt_system_scheduler_init(void)
{
    register rt_base_t offset;

    /* 线程就绪列表初始化 */
    for (offset = 0; offset < RT_THREAD_PRIORITY_MAX; offset ++)
    {
        rt_list_init(&rt_thread_priority_table[offset]);
    }

    /* 初始化当前线程控制块指针 */
    rt_current_thread = RT_NULL;

    /* 初始化线程休眠列表，当线程创建好没有启动之前会被放入到这个列表 */
    rt_list_init(&rt_thread_defunct);
}

/* 启动系统调度器 */
void rt_system_scheduler_start(void)
{
    register struct rt_thread *to_thread;

    /* 手动指定第一个运行的线程 */
    to_thread = rt_list_entry(rt_thread_priority_table[0].next,
                                struct rt_thread,
                                tlist);
    rt_current_thread = to_thread;

    /* 切换到第一个线程，该函数在context_rvds.S中实现，在rthw.h声明，
       用于实现第一次任务切换。当一个汇编函数在C文件中调用的时候，
       如果有形参，则执行的时候会将形参传人到CPU寄存器r0。*/
    rt_hw_context_switch_to((rt_uint32_t)&to_thread->sp);
}

/* 系统调度 */
void rt_schedule(void)
{
    struct rt_thread *to_thread;
    struct rt_thread *from_thread;

    /* 两个线程轮流切换 */
    if( rt_current_thread == rt_list_entry( rt_thread_priority_table[0].next,
                                            struct rt_thread,
                                            tlist) )
    {
        from_thread = rt_current_thread;
        to_thread = rt_list_entry(rt_thread_priority_table[1].next,
                                  struct rt_thread,
                                  tlist);
        rt_current_thread = to_thread;
    }
    else
    {
        from_thread = rt_current_thread;
        to_thread = rt_list_entry(rt_thread_priority_table[0].next,
                                  struct rt_thread,
                                  tlist);
        rt_current_thread = to_thread;
    }
    /* 产生上下文切换 */
    rt_hw_context_switch((rt_uint32_t)&from_thread->sp,(rt_uint32_t)&to_thread->sp);
}