kern/46600: Kernel panic when interrupting process reading from pad(4)

[Aleksej Saushev <asau%inbox.ru@localhost>]

>Number:         46600
>Category:       kern
>Synopsis:       Kernel panic when interrupting process reading from pad(4)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 14 22:40:00 +0000 2012
>Originator:     asau%inbox.ru@localhost
>Release:        NetBSD 6.0_BETA2
>Organization:
>Environment:
System: NetBSD lithium 6.0_BETA2 NetBSD 6.0_BETA2 (GENERIC) #1: Fri Jun 15 
01:50:28 MSK 2012 asau@lithium:/usr/obj/sys/arch/i386/compile/GENERIC i386
Architecture: i386
Machine: i386
>Description:
        Interrupting process that reads from pad(4) device brings system down.
        Kernel crash dump isn't saved by "sync", "reboot" doesn't work either,
        manually recorded backtrace is as follows:

sleepq_reinsert
sigpost
kpsignal2
kpsignal
kpgsignal
pgsignal
ttysigintr
softinr_dispatch

trap type 6 code 0

Backtrace on second CPU is less interesting:

x86___pause
kevent1
sys___kevent50
syscall


>How-To-Repeat:
With freshly built kernel (and modules) from netbsd-6:

        mpg123 some-file.mp3 &
        cat < /dev/pad0 > test.wav # intterrupt this process, e.g. by pressing 
ctrl-C in tty.
>Fix:
        None.