kern/39035: hang when removing pcmcia card

[apb%cequrux.com@localhost]

>Number:         39035
>Category:       kern
>Synopsis:       hang when removing pcmcia card
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 25 09:10:00 +0000 2008
>Originator:     Alan Barrett
>Release:        NetBSD 4.99.66
>Organization:
Not muxh
>Environment:
System: NetBSD 4.99.66
Architecture: i386
Machine: i386
>Description:
        I have a PCMCIA card that provides a modem-like interface
        over the GPRS/UMTS cellular data system.

        When I insert the card, it is probed correctly, and I can run
        pppd over it.

        When I remove the card, the system hangs.  "com1 detached" and
        "com2 detached" are printed on the console, but then the system
        is entirely unresponsive.  I cannot even break into ddb.

        Some time ago, I used to be able to remove the card while it was
        in use with no problem.  The device drivers would print messages
        about devices being detached, and if there was an active ppp
        session if would notice that its hardware had disappeared and
        would exit.  I'd like to get that behaviour again.

>How-To-Repeat:
        Boot the system  The following messages may be relevant:

        cbb0 at pci4 dev 6 function 0: vendor 0x104c product 0x8039 (rev. 0x00)
        cardslot0 at cbb0 slot 0 flags 0
        cardbus0 at cardslot0: bus 5
        pcmcia0 at cardslot0

        Insert the PCMCIA cellular modem card.  The following messages
        appear (along with some messages from PCMCIADEBUG which I am not
        showing here):

        pcmcia0: CIS version PC Card Standard 6.1
        pcmcia0: CIS info: Novatel Wireless, Merlin UMTS Modem, U630,
        pcmcia0: Manufacturer code 0xa4, product 0x276
        com1 at pcmcia0 function 0: <Novatel Wireless, Merlin UMTS Modem, U630, 
>
        com1: ns16550a, working fifo
        com2 at pcmcia0 function 1: <Novatel Wireless, Merlin UMTS Modem, U630, 
>
        com2: ns16550a, working fifo

        Run pppd over the com1 interface.

        Terminate the pppd process.

        Remove the card.

        The system hangs, after printing "com1 detached" and "com2 detached".

>Fix:
        Unknown.

        In general, for any hot pluggable hardware, it should be
        possible to plug in or unplug the hardware at any time, even if
        the device is in use or the system is in the process of booting
        up or shutting down, and the system should not crash or hang.