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. --Andy -- 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>