Interrupt handlers executed in a different thread?

Question

I wanted to know when the processor get's interrupted and an ISR (interrupt service routine) is executed, is that executed in the context of the thread that was interrupted to handle this interrupt or is it executed in its own thread and then goes back to where it left of in the original thread?

So a context switch actually occurs when an interrupt occurs?

Answer 1

A thread isn't created to handle the interrupt (part of why system calls can sometimes fail), though you can have a special thread to handle interrupts (read about "second level interrupt handlers" in the Wikipedia article on interrupt handling; I'm not certain if Windows uses SLIHs). There is a potential context switch since the ISR runs in kernel mode. Even if the current thread is in kernel mode, some context will be saved before calling the interrupt handler.

Still looking for documentation.