kldunload DIAGNOSTIC idea...

[Scott Long]

Brian Fundakowski Feldman wrote:
> 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.
> 

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

Scott