On Wed, Mar 29, 2017 at 11:19:49AM +0200, Peter Zijlstra wrote: > On Wed, Mar 29, 2017 at 10:59:28AM +0200, Jesper Dangaard Brouer wrote: > > On Wed, 29 Mar 2017 10:12:19 +0200 > > Peter Zijlstra <pet...@infradead.org> wrote: > > > No, that's horrible. Also, wth is this about? A memory allocator that > > > needs in_nmi()? That sounds beyond broken. > > > > It is the other way around. We want to exclude NMI and HARDIRQ from > > using the per-cpu-pages (pcp) lists "order-0 cache" (they will > > fall-through using the normal buddy allocator path). > > Any in_nmi() code arriving at the allocator is broken. No need to fix > the allocator.
That's demonstrably true. You can't grab a spinlock in NMI code and the first thing that happens if this in_irq_or_nmi() check fails is ... spin_lock_irqsave(&zone->lock, flags); so this patch should just use in_irq(). (the concept of NMI code needing to allocate memory was blowing my mind a little bit)