kern/41099: CPU_INFO_FOREACH / CPU_INFO_ITERATOR issues

[rmind%NetBSD.org@localhost]

>Number:         41099
>Category:       kern
>Synopsis:       CPU_INFO_FOREACH / CPU_INFO_ITERATOR issues
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 30 14:25:00 +0000 2009
>Originator:     Mindaugas Rasiukevicius
>Release:        NetBSD -current
>Organization:
The NetBSD Project
>Environment:
>Description:

There are issues with the CPU_INFO_FOREACH / CPU_INFO_ITERATOR interface:

- Order of CPU list is not strict, therefore double-locking of CPUs 
  (eg. if (ci1 > ci2) assumptions) and locking of all CPUs is unsafe.

- There is no clear abstraction of struct cpu_info into MI and MD.

- Interface could be dynamic to support CPU attach/detach on runtime.

>How-To-Repeat:
Code inspection.
>Fix:
Implement dynamic MI interface.