Re: kldunload DIAGNOSTIC idea...

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

  • Next message: David Schultz: "Re: kldunload DIAGNOSTIC idea..." 
    Date: Tue, 20 Jul 2004 13:10:29 -0600
To: Brian Fundakowski Feldman <green@freebsd.org>

    Brian Fundakowski Feldman wrote:
    > On Tue, Jul 20, 2004 at 08:39:57PM +0200, Poul-Henning Kamp wrote:
    >
    >>In message <20040720183213.GC1009@green.homeunix.org>, Brian Fundakowski Feldma
    >>n writes:
    >>
    >>>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?
    >>
    >>That would require us to unwind the stack which I think is overkill
    >>for the purpose.
    >>
    >>The most likely case is that the thread is sleeping on something
    >>inside the kld so just checking the instruction pointer would be
    >>fine.
    >>
    >>Looking for sleep addresses inside the module might make sense too.
    >
    >
    > It's probably not overkill -- at least in my experience most of the
    > time a driver is "doing something" it is sleeping, so the address
    > will be in mi_switch() or somewhere way out there. Sleep addresses
    > on dynamic data addresses are also a lot more common than sleep
    > addresses on static/code addresses. If someone is interested in
    > doign this, it would be very informative, especially if it could
    > catch sleeps, pending timeouts, pending callouts, etc.
    >

    busdma callbacks, cam callbacks, netisr callbacks, and on and on and on.

    Scott
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