How to measure time spent in context switch

How to measure time spent in context switch in Linux i.e. the time the application stays suspended while the kernel is doing something else. I don't want to use any profiling tools. What approach should I take to write my own C code, which can also run as kernel module if required, to measure time spent accurately. Will it also require to modify the scheduler code? Does /proc gives any statistics in this regard? Ref: http://stackoverflow.com/questions/2368384/write-a-c-program-to-measure-time... -- Manavendra Nath Manav