On Sun, 2013-05-19 at 12:35 +0300, Michael S. Tsirkin wrote:

No, I was not assuming that. What I'm trying to say is that a caller
that does something like this under a spinlock:
	preempt_disable
	pagefault_disable
	error = copy_to_user
	pagefault_enable
	preempt_enable_no_resched

is not doing anything wrong and should not get a warning,
as long as error is handled correctly later.
Right?

What I see wrong with the above is the preempt_enable_no_resched(). The
only place that should be ever used is right before a schedule(), as you
don't want to schedule twice (once for the preempt_enable() and then
again for the schedule itself).

Remember, in -rt, a spin lock does not disable preemption.

-- Steve