2.4 virtual terminal timing

[Tom Schouten <doelie@zzz.kotnet.org>]

hi all,

kernel noob first post beware..
i am using a virtual terminal on i386 arch to do reaction time measurement
for a perception psychology vision/hearing experiment.

i am trying to find out if there is a direct path in 2.4.x from
keyboard interrupt, through console/tty stuff to process wakeup,
for a 2 thread process with one thread blocking on tty read, 
running SCHED_FIFO, or a single thread process with async IO.

i suspect there is no direct path to wakeup or SIGIO delivery,
so i walked the tty/console code for a day and i can't tell really. 
i got very confused. i'm not using 2.6 yet (other scheduling problems).

so, questions: 
- where exactly does wake-up after keyboard interrupt happen?
- if no direct path, how can i get reasonable timing from keyboard?
- anyone has keyboard driver code or incredibly dirty hack replacing tty code
  that can record time stamps for keys pressed/released?
- any pointers to documentation or other hints that could put me on the right track??

i'm a bit lost

cheers
tom