[uClinux-dev] Re: soft_irq()

Paul McGougan paul.mcgougan at braintree.com.au
Mon Mar 24 06:59:34 EST 2003


----- Original Message -----
From: "John Willlams" <jwilliams at itee.uq.edu.au>
To: <uclinux-dev at uclinux.org>
Cc: <uclinux-dev at uclinux.org>
Sent: Monday, March 24, 2003 9:17 PM
Subject: Re: [uClinux-dev] Re: soft_irq()


> Still, I'm curious as to why I'm getting a softirq scheduled, apparently
by
> my timer interrupt handler (nothing else is running, I'm still in the
kernel
> "dark ages"!)

You should bear in mind that the timer interrupt is also handled in two
parts. Are you sure that you're not seeing the timer bottom half execute?

The top half does hardware specific execution, updates jiffies, updates the
execution times of processes (on SMP systems) and then schedules the timer
bottom half. The bottom half updates the internal linux time (not jiffies,
but wall time) and then process all kernel timers, on-calling functions for
any that have expired. So quite a bit of stuff can happen in the timer
bottom half.

Paul McGougan
Braintree Communications




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