Re: [RFC PATCH v9 02/13] x86: always set IF before oopsing from page fault

[Tycho Andersen <tycho@tycho.ws>]

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@oracle.com> wrote:
> >
> > From: Tycho Andersen <tycho@tycho.ws>
> >
> > 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?

Tycho