On Thu, 15 Feb 2007 22:14:45 -0800 Dan Hecht [off-list ref] wrote:

quoted

 config PREEMPT
 	bool "Preemptible Kernel (Low-Latency Desktop)"
+	depends on !XEN
 	help
 	  This option reduces the latency of the kernel by making
 	  all kernel code (that is not executing in a critical section)

Oh, so that's why it doesn't break when CONFIG_PREEMPT=y.  In which case
that preempt_disable() I spotted is wrong-and-unneeded.

Why doesn't Xen work with preemption??

I hate to sound like a broken record, but this really isn't the right 
way to do this.  If you are going to inhibit config settings when Xen 
support is compiled, then it should be:

config XEN
     depends on !KEXEC && !DOUBLEFAULT && HZ_100 && !PREEMPT

Agree.