Re: kldunload DIAGNOSTIC idea...

From: Doug Rabson (dfr_at_nlsystems.com)
Date: 07/21/04

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    To: Poul-Henning Kamp <phk@phk.freebsd.dk>
Date: Wed, 21 Jul 2004 11:37:50 +0100

    On Wed, 2004-07-21 at 10:21, Poul-Henning Kamp wrote:
    > In message <200407211010.08159.dfr@nlsystems.com>, Doug Rabson writes:
    >
    > >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.
    >
    > That is not enough. All methods in cdevsw, and things not in cdevsw
    > (clone handlers, call backs, etc etc) needs to refcount.
    >
    > I have a lot of this working in a tree here, and will commit it once
    > I have gone over it a few more times.

    Methods in cdevsw which can't be called unless the device is opened can
    rely on a single counter managed by open/close in most cases. Other
    callbacks may or may not need extra handling depending on whether or not
    the callback can persist past close.

    Will you use the existing device_busy() counter or will each driver use
    its own counter?

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