Re: atomic copy_from_user?

[Rob Love]

On Mon, 2003-12-22 at 16:59, Joe Korty wrote:

>  I do not see why a non-preempt kernel would care at all about
> the value of preempt_count.  (kmap_atomic is obviously setting it,
> where is the place in a non-preempt kernel where the set value
> is being acted upon?).

Last I checked, the architecture-specific page fault handlers.  They do
something like:

	if (in_atomic())
		goto do_not_service_fault;

This let us implement the atomic copy_*_user() functions.

kmap_atomic() needs to mark the system atomic, so the in_atomic() will
fail.

This was done around ~2.5.30 by akpm.

	Rob Love


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