bfb4a0a2c1
Xcpustop(). %es is used in at least the call to savectx() when savectx() calls bcopy(), so not loading it was fatal if a stop IPI interrupts user mode. This reduces bugs starting and stopping CPUs for debuggers. CPUs are stopped mainly in kdb_trap() and cpu_reset(). At reset time there is a good chance that all the CPUs are in the kernel, so the bug was probably harmless then.