kern/51420: gdb hangs waiting for traced threaded child under compat_netbsd32

[martin%NetBSD.org@localhost]

>Number:         51420
>Category:       kern
>Synopsis:       gdb hangs waiting for traced threaded child under compat_netbsd32
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 17 13:10:00 +0000 2016
>Originator:     Martin Husemann
>Release:        NetBSD 7.99.35
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD supremacy.duskware.de 7.99.35 NetBSD 7.99.35 (ERLITE) #170: Wed Aug 17 10:29:15 CEST 2016 martin%night-owl.duskware.de@localhost:/usr/src/sys/arch/evbmips/compile/ERLITE evbmips
Architecture: mips64eb
Machine: evbmips
>Description:

Running a compat_netbsd32 process under gdb makes gdb miss the child 
termination. The traced child process waits to be collected but parent
never wakes up.

>How-To-Repeat:
gdb dig
run

>Fix:
n/a