Re: kldunload DIAGNOSTIC idea...

From: Scott Long (scottl_at_samsco.org)
Date: 07/20/04

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    Date: Tue, 20 Jul 2004 13:08:54 -0600
To: Brian Fundakowski Feldman <green@freebsd.org>

    Brian Fundakowski Feldman wrote:
    > On Tue, Jul 20, 2004 at 08:20:23PM +0200, Poul-Henning Kamp wrote:
    >
    >>I'm pulling hair out trying to make it guaranteed safe to unload device
    >>driver modules, and the major pain here is to make sure there is no
    >>thread stuck somewhere inside the code.
    >>
    >>That gave me the idea for a simple little DIAGNOSTIC check for kldunload:
    >>run through the proc/thread table and look for any thread with an
    >>instruction counter inside the range of pages we are going to unload.
    >>
    >>Any takers ?
    >
    >
    > You mean any thread with a stack trace that includes an instruction
    > counter inside those pages, don't you?
    >

    This is better than phk's suggestion since you can have module code
    that calls out to another part of the system and blocks. Still, it's
    not 100% perfect. There are all sorts of APIs out there that do async
    callbacks, and it really should be up to the driver to track these
    things.

    Scott
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