> On Thu, May 07, 2015 at 12:50:53PM +0200, David Hildenbrand wrote: > > Just to make sure we have a common understanding (as written in my cover > > letter): > > > > Your suggestion won't work with !CONFIG_PREEMPT (!CONFIG_PREEMPT_COUNT). If > > there is no preempt counter, in_atomic() won't work. > > But there is, we _always_ have a preempt_count, and irq_enter() et al. > _always_ increment the relevant bits. > > The thread_info::preempt_count field it never under PREEMPT_COUNT > include/asm-generic/preempt.h provides stuff regardless of > PREEMPT_COUNT. > > See how __irq_enter() -> preempt_count_add(HARDIRQ_OFFSET) -> > __preempt_count_add() _always_ just works. Okay thinking about this further, I think I got your point. That basically means that the in_atomic() check makes sense for irqs. But in my opinion, it does not help do replace preempt_disable() pagefault_disable() by preempt_disable() (as discussed because of the PREEMPT_COUNT stuff) So I agree that we should better add it to not mess with hard/soft irq. > > Its only things like preempt_disable() / preempt_enable() that get > munged depending on PREEMPT_COUNT/PREEMPT. > But anyhow, opinions seem to differ how to best handle that whole stuff. I think a separate counter just makes sense, as we are dealing with two different concepts and we don't want to lose the preempt_disable =^ NOP for !CONFIG_PREEMPT. I also think that pagefault_disable() rt = copy_from_user() pagefault_enable() is a valid use case. So any suggestions how to continue? Thanks! David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>