kldunload DIAGNOSTIC idea...
Brian Fundakowski Feldman
green at freebsd.org
Tue Jul 20 11:52:38 PDT 2004
On Tue, Jul 20, 2004 at 08:39:57PM +0200, Poul-Henning Kamp wrote:
> In message <20040720183213.GC1009 at 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.
--
Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\
<> green at FreeBSD.org \ The Power to Serve! \
Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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