On Wed, Apr 3, 2019 at 6:42 PM Tycho Andersen <tycho@xxxxxxxx> wrote: > > On Wed, Apr 03, 2019 at 05:12:56PM -0700, Andy Lutomirski wrote: > > On Wed, Apr 3, 2019 at 10:36 AM Khalid Aziz <khalid.aziz@xxxxxxxxxx> wrote: > > > > > > From: Tycho Andersen <tycho@xxxxxxxx> > > > > > > Oopsing might kill the task, via rewind_stack_do_exit() at the bottom, and > > > that might sleep: > > > > > > > > > > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c > > > index 9d5c75f02295..7891add0913f 100644 > > > --- a/arch/x86/mm/fault.c > > > +++ b/arch/x86/mm/fault.c > > > @@ -858,6 +858,12 @@ no_context(struct pt_regs *regs, unsigned long error_code, > > > /* Executive summary in case the body of the oops scrolled away */ > > > printk(KERN_DEFAULT "CR2: %016lx\n", address); > > > > > > + /* > > > + * We're about to oops, which might kill the task. Make sure we're > > > + * allowed to sleep. > > > + */ > > > + flags |= X86_EFLAGS_IF; > > > + > > > oops_end(flags, regs, sig); > > > } > > > > > > > > > NAK. If there's a bug in rewind_stack_do_exit(), please fix it in > > rewind_stack_do_exit(). > > [I trimmed the CC list since google rejected it with E2BIG :)] > > I guess the problem is really that do_exit() (or really > exit_signals()) might sleep. Maybe we should put an irq_enable() at > the beginning of do_exit() instead and fix this problem for all > arches? > Hmm. do_exit() isn't really meant to be "try your best to leave the system somewhat usable without returning" -- it's a function that, other than in OOPSes, is called from a well-defined state. So I think rewind_stack_do_exit() is probably a better spot. But we need to rewind the stack and *then* turn on IRQs, since we otherwise risk exploding quite badly.
