Is there a way to find out which object called another?

Hi!
I just ran into a problem, I need to find out which object called
another object so the proper code can be run.
I'm implementing a rudimentary scheduler for software tasks.
1. I got a couple of run queues (which a pretty much vectors)
2. I got tasks which are bound to those run queues (each task only to
1 queue)
3. the scheduler is called every time a task stalls, and then needs to
do rescheduling (changing the order in the run queue, adding or
removing tasks)

My problem now is that the scheduler is only supposed to modifiy the
run queue in which the task is present which called the scheduler. Is
that possible? I know which tasks are in which run queue so I would
just need some sort of handle to the calling task to look it up.

Thanks for any help :)

great group btw learned so much so far just while reading posts :)