On Tue, 2008-04-29 at 07:00 +0200, Nick Piggin wrote: > > At this point, the spinlock is not guaranteed to have ordered the previous > stores to initialize the pte page with the subsequent store to put it in the > page tables. So another Linux page table walker might be walking down (without > any locks, because we have split-leaf-ptls), and find that new pte we've > inserted. It might try to take the spinlock before the store from the other > CPU initializes it. And subsequently it might read a pte_t out before stores > from the other CPU have cleared the memory. Funny, we used to have a similar race where the zeros for clearing a newly allocated anonymous pages end up reaching the coherency domain after the new PTE in set_pte, causing memory corruption on threaded apps. I think back then we fixed that with an explicit smp_wmb() before a set_pte(). Maybe we need that also when setting the higher levels. Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
