atomic_add

Function Usage

This function is used to perform an atomic addition on integer variables.

Procedure

Code on x86:

static inline void atomic_add(int i, atomic_t *v) 
{ 
    asm volatile(LOCK_PREFIX "addl %1,%0" : "+m" (v->counter) : "ir" (i)); 
}

Code on the Kunpeng platform:

• Method 1: Use the atomic operation functions provided by the GCC.

  static inline void atomic_add(atomic_t *v)
  {
      __sync_add_and_fetch(&((*v).counter), 1);
  }

• Method 2: Use the inline assembly to replace the code.

  static inline void atomic_add(atomic_t *v)
  {
      unsigned int tmp;
      int result, i;
      i = 1;
      __asm__ volatile(" prfm pstl1strm, %2\n"
                       "1: ldaxr %w0, %2\n" // Load data to the register.
                       " add %w0, %w0, %w3\n" // Perform an add operation.
                       " stlxr %w1, %w0, %2\n" // Write the addition result to the memory and check whether the data is successfully written.
                       "cbnz %w1, 1b" // If the data write operation fails, perform the add operation again.
                       : "=&r"(result), "=&r"(tmp), "+Q"(v->counter)
                       : "Ir"(i));
  }