On 08/25, Linus Torvalds wrote: > > On Mon, Aug 25, 2014 at 10:09 AM, Oleg Nesterov <o...@redhat.com> wrote: > > > > I'd like to change it only because this code is the main source of the > > nasty special case, used_math() and/or __thread_has_fpu(current) can be > > false even if use_eager_fpu(). > > Well, if you think it is correct (apart from missing preemption), then > I disagree *violently* with your "clean it up by restoring things > twice" model.
OK. > The signal handling overhead of floating point restore is not small, > and it's not theoretical. Again, this only if 32bit && use_eager_fpu(), and use_eager_fpu() adds this overhead to every context switch. But you convinced me anyway. If this hack doesn't look "obviously safe and correct", lets forget it. I'll try to play with copy_from_user_in_atomic(), if nothing else just to complete the discussion and see how the code can look in this case. Thanks! Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
