龙芯BSP调度器和中断控制器存在设计缺陷

发布于 2021-10-22 12:09:09 浏览：1197 订阅该版

[tocm]

## 问题1
调度器问题，调度器调度时在rt_hw_context_switch中完成了上下文切换，然后直接切换到了to_thread线程，导致下面的rt_hw_interrupt_enable在切换线程前得不到执行(ARM架构中是执行rt_hw_interrupt_enable打开中断后在PENSV中完成了上下文切换)
![image.png](https://oss-club.rt-thread.org/uploads/20211022/84402cb8a059a4f511007e5bc3701de5.png.webp)

## 问题2
中断环境不是全局管理的，每个线程都有一个中断环境，通过测试日志可以看出来main线程中关闭了中断，系统依然还能正常调度（与问题1有关），在test_thread线程中读取中断发现中断为打开状态，而main线程中断为关闭状态

在mips架构的stack.c中发现每个线程栈都初始化了cp0_status,这个寄存器正是跟中断有关的寄存器
![image.png](https://oss-club.rt-thread.org/uploads/20211022/16c6af90176bcd43533231b1b98c4a78.png.webp)

![image.png](https://oss-club.rt-thread.org/uploads/20211022/ebb15284d34a8df1574b2c8747288655.png.webp)

```c
rt_uint8_t *rt_hw_stack_init(void *tentry, void *parameter, rt_uint8_t *stack_addr, void *texit)
{
    static rt_ubase_t wSR=0;
    static rt_ubase_t wGP;
    rt_uint8_t *stk;

struct pt_regs *pt;

rt_uint32_t i;

/* Get stack aligned */
    stk = (rt_uint8_t *)RT_ALIGN_DOWN((rt_ubase_t)stack_addr, 8);
    stk -= sizeof(struct pt_regs);
    pt =  (struct pt_regs*)stk;

#ifndef ARCH_MIPS64
    for (i = 0; i < 8; ++i)
    {
        pt->pad0[i] = 0xdeadbeef;
    }
#endif
    /* Fill Stack register numbers */
    for (i = 0; i < 32; ++i)
    {
        pt->regs[i] = 0xdeadbeef;
    }

pt->regs[REG_SP] = (rt_ubase_t)stk;
    pt->regs[REG_A0] = (rt_ubase_t)parameter;
    pt->regs[REG_GP] = (rt_ubase_t)$GP;
    pt->regs[REG_FP] = (rt_ubase_t)0x0;
    pt->regs[REG_RA] = (rt_ubase_t)texit;

pt->hi  = 0x0;
    pt->lo  = 0x0;
    pt->cp0_status = (ST0_IE | ST0_CU0 | ST0_IM);
#ifdef RT_USING_FPU
    pt->cp0_status |= (ST0_CU1 | ST0_FR);
#endif
    pt->cp0_cause   = read_c0_cause();
    pt->cp0_epc = (rt_ubase_t)tentry;
    pt->cp0_badvaddr    = 0x0;

return stk;
}

```

测试代码：
```
#include <rtthread.h>
#include <mips_regs.h>

void test_thread(void* par)
{
    while (1)
    {
        rt_kprintf("[%d] (%X)  test_thread\n", rt_tick_get(), read_c0_status() & ST0_IE);
        rt_thread_mdelay(500);
    }
}

int main(int argc, char **argv)
{
    rt_thread_t tid = RT_NULL;
    tid = rt_thread_create("test", test_thread, RT_NULL,
                           20480, 21, 20);
    if(tid)
        rt_thread_startup(tid);

rt_kprintf("[%d] (%X) Hi, this is RT-Thread!!\n", rt_tick_get(), read_c0_status() & ST0_IE);
    rt_kprintf("rt_hw_interrupt_disable \n");
    rt_hw_interrupt_disable();

while(1)
    {
        rt_kprintf("[%d] (%X) Hi, this is RT-Thread!!\n", rt_tick_get(), read_c0_status() & ST0_IE);
        rt_thread_mdelay(1000);
    }
    return 0;
}

```

测试日志截图：
![image.png](https://oss-club.rt-thread.org/uploads/20211022/791c08b5824215d3c3b078ab5c5e32e3.png.webp)