Re: kldunload DIAGNOSTIC idea...

From: Poul-Henning Kamp (phk_at_phk.freebsd.dk)
Date: 07/21/04

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    To: Doug Rabson <dfr@nlsystems.com>
Date: Wed, 21 Jul 2004 13:37:50 +0200

    In message <1090408854.7114.8.camel@builder02.qubesoft.com>, Doug Rabson writes
    :

    >> There are three parts to it, a refcount on cdevsw which tells us if
    >> any thread is inside the driver using that route, a refcount on the
    >> individual cdev and a linkage between the two.
    >
    >The device_busy() counter is still simplest (as long as there is a
    >device_t at all). The implementation of devclass_delete_driver() will
    >automatically veto the unload (when its called from
    >driver_module_handler()).

    The problem is that I cannot find the device_t without dereferencing
    the struct cdev (either for si_driver[12] or the dev_t) and by then
    it is too late. There is no way we can avoid refcounting on the cdev. 

    -- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.
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