freebsd-5.4-stable panics

[Don Lewis]

On 30 Sep, Antoine Pelisse wrote:
>  Hi Robert,
> I don't think your patch is correct, the total linked list can be broken
> while the lock is released, thus just passing the link may not be enough
> I have submitted a PR[1] for this a month ago but nobody took care of it yet

There are two problems with your patch:

	sched_lock needs to be held while iterating over the threads

	sysctl_kern_proc() calls sysctl_out_proc() multiple times in a
	loop in the !KERN_PROC_PID case, so the buffer needs to be wired
	before calling sysctl_out_proc().

Is _PHOLD()/_PRELE() needed if we don't drop PROC_LOCK?

Passing a size estimate to sysctl_wire_old_buffer() is desirable, but
sysctl_out_proc() would need some restructuring to do this correctly.