About kernel function _CPU_Counter_difference overflow issue

[wangqiang3 at sugon.com]

Hello,
    When reading profiling code, I found function 
'_CPU_Counter_difference' may overflow, and it will result in 
'per_cpu->max_interrupt_time'  become a wrong larger value.
    If a cpu counter is 32bit, and it's resolution is 800ns, the counter 
will overflow every 3436 seconds(_CPU_Counter_read).
    Then, 
_Profiling_Outer_most_interrupt_entry_and_exit->_CPU_Counter_difference 
will have a incorrect result. 
 
    So,
    1. Is it a bug?
    static inline CPU_Counter_ticks _CPU_Counter_difference(
        CPU_Counter_ticks second, 
       CPU_Counter_ticks first)  
    { 
         return second - first; 
    } 
    2. If it is, I want to fix it as blow:
    #define MAX_COUNT_TICKS (0xFFFFFFFF)
    static inline CPU_Counter_ticks _CPU_Counter_difference(
        CPU_Counter_ticks second, 
       CPU_Counter_ticks first)  
    { 
        if (second > first) {
            return second - first; 
        } else {
           return MAX_COUNT_TICKS - first + second;
        }
    } 

Regards!
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