From owner-freebsd-hackers  Fri Jun 29  1: 1:47 2001
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Date: Fri, 29 Jun 2001 01:02:16 -0700
From: Terry Lambert <tlambert2@mindspring.com>
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To: vinu pattery <vinupattery@hotmail.com>
Cc: freebsd-hackers@FreeBSD.ORG
Subject: Re: interrupt on to Kernel
References: <LAW2-F146DbH8J0sca000004399@hotmail.com>
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vinu pattery wrote:
> 
> Could some body let me know, how to hack the FReeBSD kernel
> to learn the exact sequence of steps which happen when the
> device driver interrupts the FreeBSD Kernel for resources.
> Is there a trace debugger available, with which i can find
> out the steps.

It's not clear what you mean by "interrupt the Kernel for
resources"... the only resources you can grab at interrupt
are things that you pre-allocated, things you get from a
zalloci() from a previously established interrupt safe zone
in the zone allocator (e.g. mbufs), and CPU time.

As far as your tracing question: "man ddb"; you can set
breakpoints in the kernel, and step through them.  You
probably _don't_ want to do this in an interrupt routine,
but you could.

You may want to look at the FreeBSD Handbook, and at the
device driver and bus articles on:

	http://www.daemonnews.org/

There is also a (fairly old) "Device Driver Writer's Guide":

	http://freebsd.dei.uc.pt/tutorials/ddwg/ddwg.html

-- Terry

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