kern/39131: drvctl -d com1 crashes the system

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>Number:         39131
>Category:       kern
>Synopsis:       drvctl -d com1 crashes the system
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jul 11 17:35:00 +0000 2008
>Originator:     Alan Barrett
>Release:        NetBSD 4.99.69
>Organization:
Not much
>Environment:
System: NetBSD 4.99.69
Architecture: i386
Machine: i386
>Description:
        I wanted to unplug a pcmcia modem card.  Due to the problem in
        PR 39035, I decided to try "drvctl -u pcmcia0" before physically
        removing the card.  That didn't work, so I tried "drvctl -u com1"
        (where com1 is one of the two com ports on this pcmcia card).
        The system paniced.

>How-To-Repeat:
        Start with a pcmcia card that has com1 at pcmcia0 and com2 at
        pcmcia0.

        $ sudo drvctl -d pcmcia0
        drvctl: DRVDETACHDEV: Not supported
        $ sudo drvctl -d com1
        com1: detached
        WARNING: SPL NOT LOWERED ON SYSCALL EXIT
        panic: cpu_switchto: switching above IPL_SCHED (8)
        fatal breakpoint trap in supervisor mode
        trap type 1 code 0 eip c04ff34c cs 8 eflags 246 cr2 bbbb4904 ilevel 8
        stopped in pid 25663.1 (drvctl) at netbsd:breakpoint+0x5: popl %ebp
        db{1}>

>Fix:
        Unknown