linux-kernel - Re: [regression drm/noveau] suspend to ram -> BOOM: exception RIP: drm_calc_vbltimestamp_from

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Date:   Fri, 14 Jul 2017 17:58:18 +0200
From:   Mike Galbraith <efault@....de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ilia Mirkin <imirkin@...m.mit.edu>,
        LKML <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        Ben Skeggs <bskeggs@...hat.com>, jeyu@...nel.org
Subject: Re: [regression drm/noveau] suspend to ram -> BOOM: exception RIP:
 drm_calc_vbltimestamp_from_scanoutpos+335

On Fri, 2017-07-14 at 17:50 +0200, Peter Zijlstra wrote:
> On Fri, Jul 14, 2017 at 03:36:08PM +0200, Mike Galbraith wrote:
> > Ok, a network outage gave me time to go hunting.  Indeed it is a bad
> > interaction with the tree DRM merged into.  All DRM did was to slip a
> > WARN_ON_ONCE() that nouveau triggers into a kernel module where such
> > things no longer warn, they blow the box out of the water.  I made a
> > dinky testcase module (attached), and bisected to the real root....
> > 
> > 19d436268dde95389c616bb3819da73f0a8b28a8 is the first bad commit
> > commit 19d436268dde95389c616bb3819da73f0a8b28a8
> > Author: Peter Zijlstra <peterz@...radead.org>
> > Date:   Sat Feb 25 08:56:53 2017 +0100
> > 
> >     debug: Add _ONCE() logic to report_bug()
> 
> Urgh, is for some mysterious reason the __bug_table section of modules
> ending up in RO memory?
> 
> I forever get lost in that link magic :/

+1

drm.ko
 20 __bug_table   00000630  0000000000000000  0000000000000000  0004bff3  2**0
                  CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA
vmlinux
 15 __bug_table   0000ba84  ffffffff81af26c0  0000000001af26c0  00cf26c0  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA

Danged if I know... um um RELOC business mucks things up?

	-Mike