kern/39342: cpuctl hangs in xc_wait

[joerg%britannica.bec.de@localhost]

>Number:         39342
>Category:       kern
>Synopsis:       cpuctl offline hangs in xc_wait
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Aug 11 14:45:00 +0000 2008
>Originator:     joerg%britannica.bec.de@localhost
>Release:        NetBSD 4.99.68
>Organization:
TNF
>Environment:
        
        
System: NetBSD britannica.bec.de 4.99.68 NetBSD 4.99.68 (LATITUDE) #0: Thu Jul 
3 18:12:03 CEST 2008 
joerg%britannica.bec.de@localhost:/data/NetBSD/wapbl/src/sys/arch/amd64/compile/LATITUDE
 amd64
Architecture: x86_64
Machine: amd64
>Description:
For a while "cpuctl offline cpu1" immediate after boot -s will hang and
never return. Further debugging shows that the problem happens whenever
cpuctl is asked to stop the CPU the task is running on.

Adding a forced yield before the xc_wait makes the offline part work,
but the process is still stuck.

>How-To-Repeat:

Run cpuctl offline a number of time with some cpu intensive processes in
the background.

>Fix:
-

>Unformatted: