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

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Date:   Thu, 4 Apr 2019 18:23:50 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Tycho Andersen <tycho@...ho.ws>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Khalid Aziz <khalid.aziz@...cle.com>,
        iommu@...ts.linux-foundation.org, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Khalid Aziz <khalid@...ehiking.org>
Subject: Re: [RFC PATCH v9 02/13] x86: always set IF before oopsing from page
 fault

- stepping on del button while browsing though CCs.
On 2019-04-04 09:47:27 [-0600], Tycho Andersen wrote:
> > 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.
> 
> Ok, sounds good. I guess we can include something like this patch in
> the next series.

The tracing infrastructure probably doesn't know that the interrupts are
back on. Also if you were holding a spin lock then your preempt count
isn't 0 which means that might_sleep() will trigger a splat (in your
backtrace it was zero).

> Thanks,
> 
> Tycho
Sebastian