port-i386/38989: crash switching from text to graphics console

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>Number:         38989
>Category:       port-i386
>Synopsis:       crash switching from text to graphics console
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 19 16:25:00 +0000 2008
>Originator:     Alan Barrett
>Release:        NetBSD 4.99.63
>Organization:
Not much
>Environment:
System: NetBSD 4.99.63
Architecture: i386
Machine: i386
>Description:
        The system may crash when switching from a text console to a
        graphical console, when using wscons with multiple virtual
        consoles.

>How-To-Repeat:
        I was running X on the wscons virtual console that's accessed
        by pressing alt-control-F5.

        I switched to the first virtual console (which was in text mode)
        by pressing alt-control-F1.

        A short time later, I attempted to switch back to the X session
        by pression alt-control-F5, but the system crashed.

        Some of the messages had scrolled off the screen before I saw
        them, but here's a partial backtrace:

Stoped in pid 1138.1 (Xorg) ...
_bus_dmamem_alloc_range(...)
_bus_dmamem_alloc(...)
agp_generic_bind_memory(...)
cdev_ioctl(...)
dev_ioctl(...)
spec_ioctl(...)
VOP_IOCTL(...)
vn_ioctl(...)
sys_ioctl(...)
syscall(...)

>Fix:
        Switching from a text console to a graphics console sometimes
        works.  In this case, I suspect that there was insufficient free
        memory.

        If the problem is memory allocation, then a possible fix could
        be to free some memory and try again instead of crashing.