Date: Wed, 21 Jul 2004 10:10:07 +0100 From: Doug Rabson <dfr@nlsystems.com> To: freebsd-arch@freebsd.org Cc: arch@freebsd.org Subject: Re: kldunload DIAGNOSTIC idea... Message-ID: <200407211010.08159.dfr@nlsystems.com> In-Reply-To: <40FD6E25.1080808@samsco.org> References: <20040720183213.GC1009@green.homeunix.org> <20040720185236.GD1009@green.homeunix.org> <40FD6E25.1080808@samsco.org>
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On Tuesday 20 July 2004 20:10, Scott Long wrote: > 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. The original intention was that drivers use the device_busy()/device_unbusy() counter to handle these things. In some cases, just calling device_busy() from fooopen() and device_unbusy() from fooclose() is sufficient.
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