On Thu, May 07, 2015 at 01:23:35PM +0200, David Hildenbrand wrote: > > 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. > > > > Its only things like preempt_disable() / preempt_enable() that get > > munged depending on PREEMPT_COUNT/PREEMPT. > > > > Sorry for the confusion. Sure, there is always the count. > > My point is that preempt_disable() won't result in an in_atomic() == true > with !PREEMPT_COUNT, so I don't see any point in adding in to the pagefault > handlers. It is not reliable. It _very_ reliably tells if we're in interrupts! Which your patches break. It also very much avoids touching two cachelines in a number of places. -- 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>