K 10
svn:author
V 7
fabient
K 8
svn:date
V 27
2011-03-31T13:59:47.937145Z
K 7
svn:log
V 575
Clearing the flag when preempting will let the preempted thread run
too much time. This can finish in a scheduler deadlock with ping-pong
between two threads.

One sample of this is:
- device lapic (to have a preemption point on critical_exit())
- options DEVICE_POLLING with HZ>1499 (to have lapic freq = hardclock freq)
- running a cpu intensive task (that does not enter the kernel)
- only one CPU on SMP or no SMP.

As requested by jhb@ 4BSD have received the same type of fix instead of
propagating the flag to the new thread.

Reviewed by:	jhb, jeff
MFC after:	1 month

END