All backports from the 2.4 code

into home.transmeta.com:/home/torvalds/v2.5/linux

into tetrachloride.(none):/mnt/stuff/kernel/2.5/watchdog

into tetrachloride.(none):/mnt/stuff/kernel/2.5/watchdog

into home.transmeta.com:/home/torvalds/v2.5/linux

into tetrachloride.(none):/mnt/stuff/kernel/2.5/agpgart

version before looking at more complicated changes.

This fixes a potential problem in the migration thread for the case that
the first CPU in the cpus_allowed mask of a process is offline.