In .NET, the Thread class has the functions VolatileRead and VolatileWrite (and similar Volatile.Read / Volatile.Write ):

 [MethodImplAttribute(MethodImplOptions.NoInlining)] // disable optimizations public static int VolatileRead(ref int address) { int ret = address; MemoryBarrier(); // Call MemoryBarrier to ensure the proper semantic in a portable way. return ret; } [MethodImplAttribute(MethodImplOptions.NoInlining)] // disable optimizations public static void VolatileWrite(ref int address, int value) { MemoryBarrier(); // Call MemoryBarrier to ensure the proper semantic in a portable way. address = value; }

I do not quite understand why memory barriers stand in these places. For example, in VolatileRead , why not need a barrier to reading the value? In addition, these methods are not inline, can the processor rearrange instructions through call / ret?

  • I think it can rearrange, otherwise even the call of an empty function would be a complete barrier. - VladD
  • @VladD yes, indeed, both call and ret can be rearranged on stackoverflow.com/questions/38261098 - kmv

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