Re: newbus integration of MOD_QUIESCE

From: M. Warner Losh (imp_at_bsdimp.com)
Date: 07/14/04

  • Next message: Robert Watson: "Re: newbus integration of MOD_QUIESCE" 
    Date: Tue, 13 Jul 2004 18:14:19 -0600 (MDT)
To: rwatson@freebsd.org

    In message: <Pine.NEB.3.96L.1040713195126.63836A-100000@fledge.watson.org>
                Robert Watson <rwatson@freebsd.org> writes:
    : MOD_WEAKUNLOAD - Unload if you're not in use. I.e., unattached driver,
    : unmounted file system, netgraph nodes that aren't instantiated, network
    : protocol without any sockets, etc. Be harmlessly gone, but vetoed
    : at a low cost.

    This is desirable.

    : MOD_STRONGUNLOAD - Unload even though you're in use. Detach the driver,
    : deadfs the file system, wither the geom, sever the sockets, etc. May
    : cause disruption, but may also veto, depending on the subsystem,
    : especially if the subsytem has no way to notify its consumers of
    : impending doom. Can be vetoed, but try harder before vetoing. Some
    : subsystems might always return EBUSY for this if there's really no way
    : to express "undesirable departure" upwards.

    This is tue current MOD_UNLOAD

    : MOD_QUIESCE - Attempt MOD_WEAKUNLOAD, and if that fails, ask the module to
    : start draining in some form. I'm a bit unclear on quite what's
    : intended, but this seems to be less atomic notion than "unload, or
    : don't" at various points on the spectrum. I.e., it kicks off a state
    : transition in what is likely a slightly poorly defined state machine.
    : Right now, the state machine is "Not loaded", "Loaded", and we use a
    : lock to prevent intermediate states from colliding.

    This is the heart of my questions about MOD_QUIESCE.

    Warner
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