Man page 9 : work_on_cpu

work_on_cpu - run a function in user context on a particular cpu

long work_on_cpu(int  cpu , long (* fn ) (void *), void *  arg );

cpu
    the cpu to run on

fn
    the function to run

arg
    the function arg

This will return the value fn returns. It is up to the caller to ensure that the cpu doesnAqt go offline. The caller must not hold any locks which would prevent fn from completing.