通过引用将字段传递到非托管代码中安全吗

通过引用将字段传递到非托管外部方法中安全吗？

[StructLayout(LayoutKind.Sequential)]
struct SomeStruct
{
    public int SomeValue;
}
class SomeClass
{
    SomeStruct _someStruct;
    [DllImport("SomeLibrary.dll")]
    static extern void SomeExternMethod(ref SomeStruct someStruct);
    public void SomeMethod()
    {
        // Is this safe or do I have to pin the current instance of SomeClass?
        SomeExternMethod(ref _someStruct);
    }
}