RT-Thread 4.0.2初次上下文切换失败

发布于 2020-08-23 10:05:35 浏览：1271 订阅该版

初次移植RTThread不太懂，使用的是MDK5.30，芯片平台是STM32H750系列，先打算移植内核和FinSH组件，但是失败了，程序无法调度。

情况：

```C
int rtthread_startup(void)
{
    rt_hw_interrupt_disable();
    rt_hw_board_init();
    rt_show_version();
    rt_system_timer_init();
    rt_system_scheduler_init();
    rt_application_init();
    rt_system_timer_thread_init();
    rt_thread_idle_init();
	extern int finsh_system_init(void);
		finsh_system_init();
    rt_system_scheduler_start();		//运行到这里
    return 0;
}
```

代码能运行到`rt_system_scheduler_start`，进入`rt_system_scheduler_start`后：

```C
void rt_system_scheduler_start(void)
{
    register struct rt_thread *to_thread;
    rt_ubase_t highest_ready_priority;
    to_thread = _get_highest_priority_thread(&highest_ready_priority);
    rt_current_thread = to_thread;
    rt_schedule_remove_thread(to_thread);
    to_thread->stat = RT_THREAD_RUNNING;
    rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp);    //进入

/* never come back */
}

```

能够移植运行到`rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp)`，进入`rt_hw_context_switch_to((rt_ubase_t)&to_thread->sp)`：

```C
rt_hw_context_switch_to    PROC
    EXPORT rt_hw_context_switch_to
    ; set to thread
    LDR     r1, =rt_interrupt_to_thread
    STR     r0, [r1]

IF      {FPU} != "SoftVFP"
    ; CLEAR CONTROL.FPCA
    MRS     r2, CONTROL             ; read
    BIC     r2, #0x04               ; modify
    MSR     CONTROL, r2             ; write-back
    ENDIF

; set from thread to 0
    LDR     r1, =rt_interrupt_from_thread
    MOV     r0, #0x0
    STR     r0, [r1]

; set interrupt flag to 1
    LDR     r1, =rt_thread_switch_interrupt_flag
    MOV     r0, #1
    STR     r0, [r1]

; set the PendSV exception priority
    LDR     r0, =NVIC_SYSPRI2
    LDR     r1, =NVIC_PENDSV_PRI
    LDR.W   r2, [r0,#0x00]       ; read
    ORR     r1,r1,r2             ; modify
    STR     r1, [r0]             ; write-back

; trigger the PendSV exception (causes context switch)
    LDR     r0, =NVIC_INT_CTRL
    LDR     r1, =NVIC_PENDSVSET
    STR     r1, [r0]

; restore MSP
    LDR     r0, =SCB_VTOR
    LDR     r0, [r0]
    LDR     r0, [r0]
    MSR     msp, r0

; enable interrupts at processor level
    CPSIE   F
    CPSIE   I

ENDP

; compatible with old version
rt_hw_interrupt_thread_switch PROC
    EXPORT rt_hw_interrupt_thread_switch
    BX      lr			;运行到这里，没有切换线程
    ENDP
```

程序直接在调度器启动的第一次上下文切换就失败了。

请问各位伙伴，这会是什么原因呢？整个周末都花这儿了，