Question to interrupts and bottom halfs

Marc Bechler (
Sat, 2 May 1998 13:34:28 +0200

First, I'm not very experienced with interrupts, so I hope that anyone
can help me. I have some problems concerning the time used for
interrupts and the execution of bottom halfs.

So here is the scenario: The running process (in user mode) was
interrupted. Then the system switches to the system mode and
enters the kernel to run the interrupt service routines (korrect?). Let's
say this service routine take 10 ms (only for demonstration). Then the
bottom halfs will be activated, so the scheduler first executes the bottom
halfs. Let's say, this takes 20 ms. Afterwards the task continues the execution.

And now my question: Will the counter of the task (and the times this
process spents in user-/kernel-mode) be decreased (increased)? What
about a interrupted process running in kernel-mode?
And a more general question: In which environment runs the interrupt service
routine and the bottom halfs? In the context of the former task or in its own

Lots of questions, but thanks for helping me


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