* Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote: > On Sun, Jun 14, 2015 at 7:47 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote: > > Oleg Nesterov <oleg@xxxxxxxxxx> writes: > >> > >> But again, the kernel no longer does this? do_page_fault() does > >> vmalloc_fault() without notify_die(). If it fails, I do not see how/why a > >> modular DIE_OOPS handler could try to resolve this problem and trigger > >> another fault. > > > > The same problem can happen from NMI handlers or machine check handlers. It's > > not necessarily tied to page faults only. > > AIUI, the point of the one and only vmalloc_sync_all call is to prevent > infinitely recursive faults when we call a notify_die callback. The only thing > that it could realistically protect is module text or static non-per-cpu module > data, since that's the only thing that's reliably already in the init pgd. I'm > with Oleg: I don't see how that can happen, since do_page_fault fixes up vmalloc > faults before it calls notify_die. Yes, but what I meant is that it can happen if due to an unrelated kernel bug and unlucky timing we have installed this new handler just when that other unrelated kernel bug triggers: say a #GPF crash in kernel code. In any case it should all be mooted with the removal of lazy PGD instantiation. Thanks, Ingo -- 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>