Timer Interrupt and Scheduler

Could someone give me more insight into how the scheduler would get called
when a timer interrupt happens? I tried tracing through the code handling the
external interrupt and am at a loss trying to figure out this part.

Thanks,

Ullas Ponnadi

I would like to expand my observations a little bit more with regards to the timer
interrupt and the scheduler.

Looking at the linux documentation available and the code for the x86 and
alpha architectures, at the very end of a return from the timer interrupt,
a call to the scheduler should be made, if necessary. I see this call in the
ret_from_intr label in entry.S file on the x86 architecture and ret_from_sys_call
in entry.S on the alpha architecture. The parisc interrupt handler does not seem to
be doing any such thing. ( Looking at the linux-2_3_29-20000208_tar archive ).

Could someone help me understand how the scheduler would get called when

a timer interrupt occurs?

Thanks,

Ullas