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Groups > linux.kernel > #1182294 > unrolled thread

[4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference

Started byJörg Otte <jrg.otte@gmail.com>
First post2015-07-12 10:10 +0200
Last post2015-07-13 11:00 +0200
Articles 7 — 3 participants

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  [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Jörg Otte <jrg.otte@gmail.com> - 2015-07-12 10:10 +0200
    Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2015-07-13 08:00 +0200
    Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer  dereference Daniel Vetter <daniel@ffwll.ch> - 2015-07-13 08:20 +0200
      Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2015-07-13 09:30 +0200
        Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Jörg Otte <jrg.otte@gmail.com> - 2015-07-13 09:50 +0200
          Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Maarten Lankhorst <maarten.lankhorst@linux.intel.com> - 2015-07-13 10:00 +0200
            Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference Jörg Otte <jrg.otte@gmail.com> - 2015-07-13 11:00 +0200

#1182294 — [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference

FromJörg Otte <jrg.otte@gmail.com>
Date2015-07-12 10:10 +0200
Subject[4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference
Message-ID<pLkuJ-5T6-1@gated-at.bofh.it>
4.2.0-rc1-00201-g59c3cb5 introducued a null pointer derefence and a
system freeze
when Xorg is started ( 4.2.0-rc1-00062-gc4b5fd3 was fine) :

BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
PGD 0
Oops: 0000 [#1] SMP
CPU: 1 PID: 1290 Comm: Xorg Not tainted 4.2.0-rc1-00201-g59c3cb5 #6
Hardware name: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
task: ffff8802149d6c00 ti: ffff880206df4000 task.ti: ffff880206df4000
RIP: 0010:[<ffffffffbd3447bb>]  [<ffffffffbd3447bb>] 0xffffffffbd3447bb
RSP: 0018:ffff880206df7b08  EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88021578f480 RCX: ffff88021578f4d0
RDX: 0000000000000000 RSI: ffff88021630b000 RDI: ffff880214a68000
RBP: ffff88021630b000 R08: ffff88021578f4e0 R09: ffff88021578f4f0
R10: 0000000000003c18 R11: 00000000fffffff2 R12: ffff880214a68000
R13: ffff88021634e800 R14: 0000000000000000 R15: 0000000000000000
FS:  00007ff3caa60880(0000) GS:ffff88021f280000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000009 CR3: 0000000206e07000 CR4: 00000000001407e0
Stack:
 ffff880200010000 ffff880200010000 ffff880200000000 ffff880200000001
 ffff88021578f500 ffffffffbd2df135 ffff880213f71c00 ffff880214a68000
 0000000000000000 ffff880214a70000 0000000000000001 ffff880214a68000
Call Trace:
 [<ffffffffbd2df135>] ? 0xffffffffbd2df135
 [<ffffffffbd2b6ca8>] ? 0xffffffffbd2b6ca8
 [<ffffffffbd33cc7e>] ? 0xffffffffbd33cc7e
 [<ffffffffbd343673>] ? 0xffffffffbd343673
 [<ffffffffbd2d0728>] ? 0xffffffffbd2d0728
 [<ffffffffbd2d088e>] ? 0xffffffffbd2d088e
 [<ffffffffbd2d10c5>] ? 0xffffffffbd2d10c5
 [<ffffffffbd2c6976>] ? 0xffffffffbd2c6976
 [<ffffffffbd2d0fe0>] ? 0xffffffffbd2d0fe0
 [<ffffffffbd0c6a1f>] ? 0xffffffffbd0c6a1f
 [<ffffffffbd0e79e1>] ? 0xffffffffbd0e79e1
 [<ffffffffbd0e7ed1>] ? 0xffffffffbd0e7ed1
 [<ffffffffbd6df557>] ? 0xffffffffbd6df557
Code: 48 89 54 24 20 48 8b 54 24 40 48 89 ee 89 0c 24 4c 89 f9 c7 44
24 18 01 00 00 00 89 44 24 08 e8 bc 1f f7 ff 85 c0 41 89 c7 75 67 <41>
80 7e 09 00 74 56 49 8b 84 24 38 02 00 00 c6 85 d0 08 00 00
RIP  [<ffffffffbd3447bb>] 0xffffffffbd3447bb
 RSP <ffff880206df7b08>
CR2: 0000000000000009
---[ end trace dd0931f7f0d43d12 ] ---
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#1182530

FromMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date2015-07-13 08:00 +0200
Message-ID<pLEWu-1cJ-9@gated-at.bofh.it>
In reply to#1182294
Op 12-07-15 om 18:52 schreef Linus Torvalds:
> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
>> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
> Ugh. Please enable KALLSYMS to get sane symbols.
>
> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
> so it's pretty clearly just that change frm
>
> -       if (intel_crtc->active) {
> +       if (crtc_state->base.active) {
>
> and "crtc_state" is NULL.
>
> And the code very much knows that crtc_state can be NULL, since it's
> initialized with
>
>         crtc_state = state->base.state ?
>                 intel_atomic_get_crtc_state(state->base.state,
> intel_crtc) : NULL;
>
> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
> ("drm/i915: Use crtc_state->active in primary check_plane func") for
> now, or is there a better fix? Like just checking crtc_state for NULL?
>
>                     Linus
More symbols would be nice.

With the transitional helpers when crtc_state == NULL you don't want to update the scalers or funny things happen.
Fix is probably something like this:

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ba9321998a41..830e07b23a15 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13276,7 +13276,7 @@ intel_check_primary_plane(struct drm_plane *plane,
 	if (ret)
 		return ret;
 
-	if (crtc_state->base.active) {
+	if (crtc_state ? crtc_state->base.active || crtc->state->active) {
 		struct intel_plane_state *old_state =
 			to_intel_plane_state(plane->state);
 

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#1182535 — Re: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference

FromDaniel Vetter <daniel@ffwll.ch>
Date2015-07-13 08:20 +0200
SubjectRe: [4.2.0-rc1-00201-g59c3cb5] Regression: kernel NULL pointer dereference
Message-ID<pLFfQ-1yq-7@gated-at.bofh.it>
In reply to#1182294
On Sun, Jul 12, 2015 at 09:52:51AM -0700, Linus Torvalds wrote:
> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
> >
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
> > IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
> 
> Ugh. Please enable KALLSYMS to get sane symbols.
> 
> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
> so it's pretty clearly just that change frm
> 
> -       if (intel_crtc->active) {
> +       if (crtc_state->base.active) {
> 
> and "crtc_state" is NULL.
> 
> And the code very much knows that crtc_state can be NULL, since it's
> initialized with
> 
>         crtc_state = state->base.state ?
>                 intel_atomic_get_crtc_state(state->base.state,
> intel_crtc) : NULL;
> 
> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
> ("drm/i915: Use crtc_state->active in primary check_plane func") for
> now, or is there a better fix? Like just checking crtc_state for NULL?

Indeed embarrassing. I've missed that we still have 1 caller left that's
using the transitional helpers, and those don't fill out
plane_state->state backpointers to the global atomic update since there is
no global atomic update for transitional helpers. Below diff should fix
this - we need to preferentially check crts_state->active and if that's
not set intel_crtc->active should yield the right result for the one
remaining caller (it's in the crtc_disable paths).

For cheap excuses why i915 is so crap in 4.2: Thanks to a hipshot decision
to transition to a different QA team ("we'll do this in 1 week without
upfront planing") I essentially don't have proper QA support for 1-2
months by now. The other trouble in this area specifically is that this
code is already completely changed in -next again, so any testing done on
integration trees (like -next or drm-intel-nightly) won't test any patches
for 4.2.
-Daniel

Oh and Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> in case you
decide to apply this right away.
---
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ba9321998a41..85ac6d85dc39 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13276,7 +13276,7 @@ intel_check_primary_plane(struct drm_plane *plane,
 	if (ret)
 		return ret;
 
-	if (crtc_state->base.active) {
+	if (crtc_state ? crtc_state->base.active : intel_crtc->active) {
 		struct intel_plane_state *old_state =
 			to_intel_plane_state(plane->state);
 
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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#1182555

FromMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date2015-07-13 09:30 +0200
Message-ID<pLGlz-2ap-1@gated-at.bofh.it>
In reply to#1182535
Op 13-07-15 om 08:22 schreef Daniel Vetter:
> On Sun, Jul 12, 2015 at 09:52:51AM -0700, Linus Torvalds wrote:
>> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
>>> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
>> Ugh. Please enable KALLSYMS to get sane symbols.
>>
>> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
>> so it's pretty clearly just that change frm
>>
>> -       if (intel_crtc->active) {
>> +       if (crtc_state->base.active) {
>>
>> and "crtc_state" is NULL.
>>
>> And the code very much knows that crtc_state can be NULL, since it's
>> initialized with
>>
>>         crtc_state = state->base.state ?
>>                 intel_atomic_get_crtc_state(state->base.state,
>> intel_crtc) : NULL;
>>
>> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
>> ("drm/i915: Use crtc_state->active in primary check_plane func") for
>> now, or is there a better fix? Like just checking crtc_state for NULL?
> Indeed embarrassing. I've missed that we still have 1 caller left that's
> using the transitional helpers, and those don't fill out
> plane_state->state backpointers to the global atomic update since there is
> no global atomic update for transitional helpers. Below diff should fix
> this - we need to preferentially check crts_state->active and if that's
> not set intel_crtc->active should yield the right result for the one
> remaining caller (it's in the crtc_disable paths).
>
> For cheap excuses why i915 is so crap in 4.2: Thanks to a hipshot decision
> to transition to a different QA team ("we'll do this in 1 week without
> upfront planing") I essentially don't have proper QA support for 1-2
> months by now. The other trouble in this area specifically is that this
> code is already completely changed in -next again, so any testing done on
> integration trees (like -next or drm-intel-nightly) won't test any patches
> for 4.2.
> -Daniel
>
> Oh and Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> in case you
> decide to apply this right away.
>
Well your version has the benefit of compiling without errors. :-)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
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#1182571

FromJörg Otte <jrg.otte@gmail.com>
Date2015-07-13 09:50 +0200
Message-ID<pLGEX-2gY-19@gated-at.bofh.it>
In reply to#1182555
2015-07-13 9:23 GMT+02:00 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
> Op 13-07-15 om 08:22 schreef Daniel Vetter:
>> On Sun, Jul 12, 2015 at 09:52:51AM -0700, Linus Torvalds wrote:
>>> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
>>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
>>>> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
>>> Ugh. Please enable KALLSYMS to get sane symbols.
>>>
>>> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
>>> so it's pretty clearly just that change frm
>>>
>>> -       if (intel_crtc->active) {
>>> +       if (crtc_state->base.active) {
>>>
>>> and "crtc_state" is NULL.
>>>
>>> And the code very much knows that crtc_state can be NULL, since it's
>>> initialized with
>>>
>>>         crtc_state = state->base.state ?
>>>                 intel_atomic_get_crtc_state(state->base.state,
>>> intel_crtc) : NULL;
>>>
>>> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
>>> ("drm/i915: Use crtc_state->active in primary check_plane func") for
>>> now, or is there a better fix? Like just checking crtc_state for NULL?
>> Indeed embarrassing. I've missed that we still have 1 caller left that's
>> using the transitional helpers, and those don't fill out
>> plane_state->state backpointers to the global atomic update since there is
>> no global atomic update for transitional helpers. Below diff should fix
>> this - we need to preferentially check crts_state->active and if that's
>> not set intel_crtc->active should yield the right result for the one
>> remaining caller (it's in the crtc_disable paths).
>>
>> For cheap excuses why i915 is so crap in 4.2: Thanks to a hipshot decision
>> to transition to a different QA team ("we'll do this in 1 week without
>> upfront planing") I essentially don't have proper QA support for 1-2
>> months by now. The other trouble in this area specifically is that this
>> code is already completely changed in -next again, so any testing done on
>> integration trees (like -next or drm-intel-nightly) won't test any patches
>> for 4.2.
>> -Daniel
>>
>> Oh and Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> in case you
>> decide to apply this right away.
>>
> Well your version has the benefit of compiling without errors. :-)
>
> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

Just noticed another problem:
On each resume I get the following error:
-----------[ cut here ]------------
WARNING: CPU: 2 PID: 2663 at
/data/kernel/linux/drivers/gpu/drm/i915/intel_display.c:6319
0xffffffff9a33d5e9()
WARN_ON(!crtc->state->enable)
CPU: 2 PID: 2663 Comm: kworker/u8:80 Not tainted 4.2.0-rc2 #15
ardware name: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
orkqueue: events_unbound 0xffffffff9a055750
0000000000000000 ffffffff9a98ea28 ffffffff9a6d84d2 0000000000000000
ffffffff9a03c416 ffff88020951c4e0 0000000000000000 0000000000000000
ffff8802141cb800 ffff88021630c000 ffffffff9a03c4d5 ffffffff9a9c3664
all Trace:
[<ffffffff9a6d84d2>] ? 0xffffffff9a6d84d2
[<ffffffff9a03c416>] ? 0xffffffff9a03c416
[<ffffffff9a03c4d5>] ? 0xffffffff9a03c4d5
[<ffffffff9a33d5e9>] ? 0xffffffff9a33d5e9
[<ffffffff9a343ac3>] ? 0xffffffff9a343ac3
[<ffffffff9a34444a>] ? 0xffffffff9a34444a
[<ffffffff9a345518>] ? 0xffffffff9a345518
[<ffffffff9a3246f0>] ? 0xffffffff9a3246f0
[<ffffffff9a2e1ce8>] ? 0xffffffff9a2e1ce8
[<ffffffff9a236170>] ? 0xffffffff9a236170
[<ffffffff9a38b28d>] ? 0xffffffff9a38b28d
[<ffffffff9a38b784>] ? 0xffffffff9a38b784
[<ffffffff9a38baa4>] ? 0xffffffff9a38baa4
[<ffffffff9a05577d>] ? 0xffffffff9a05577d
[<ffffffff9a04dc47>] ? 0xffffffff9a04dc47
[<ffffffff9a04dfab>] ? 0xffffffff9a04dfab
[<ffffffff9a04dea0>] ? 0xffffffff9a04dea0
[<ffffffff9a05331c>] ? 0xffffffff9a05331c
[<ffffffff9a053260>] ? 0xffffffff9a053260
[<ffffffff9a6dfa0f>] ? 0xffffffff9a6dfa0f
[<ffffffff9a053260>] ? 0xffffffff9a053260
--[ end trace 1b6d28ee34071679 ]---

Nervertheless resume works, so it doesn't hurt me.


BTW: I get also up to 40..50!  compile warnings like:
i915/i915_drv.h: In function 'i915_debugfs_connector_add':
i915/i915_drv.h:3119:53: warning: no return statement in function
returning non-void [-Wreturn-type]

which may cause yet uncovered troubles.

Thanks, Jörg
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#1182575

FromMaarten Lankhorst <maarten.lankhorst@linux.intel.com>
Date2015-07-13 10:00 +0200
Message-ID<pLGOB-2ka-13@gated-at.bofh.it>
In reply to#1182571
Op 13-07-15 om 09:42 schreef Jörg Otte:
> 2015-07-13 9:23 GMT+02:00 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
>> Op 13-07-15 om 08:22 schreef Daniel Vetter:
>>> On Sun, Jul 12, 2015 at 09:52:51AM -0700, Linus Torvalds wrote:
>>>> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
>>>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
>>>>> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
>>>> Ugh. Please enable KALLSYMS to get sane symbols.
>>>>
>>>> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
>>>> so it's pretty clearly just that change frm
>>>>
>>>> -       if (intel_crtc->active) {
>>>> +       if (crtc_state->base.active) {
>>>>
>>>> and "crtc_state" is NULL.
>>>>
>>>> And the code very much knows that crtc_state can be NULL, since it's
>>>> initialized with
>>>>
>>>>         crtc_state = state->base.state ?
>>>>                 intel_atomic_get_crtc_state(state->base.state,
>>>> intel_crtc) : NULL;
>>>>
>>>> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
>>>> ("drm/i915: Use crtc_state->active in primary check_plane func") for
>>>> now, or is there a better fix? Like just checking crtc_state for NULL?
>>> Indeed embarrassing. I've missed that we still have 1 caller left that's
>>> using the transitional helpers, and those don't fill out
>>> plane_state->state backpointers to the global atomic update since there is
>>> no global atomic update for transitional helpers. Below diff should fix
>>> this - we need to preferentially check crts_state->active and if that's
>>> not set intel_crtc->active should yield the right result for the one
>>> remaining caller (it's in the crtc_disable paths).
>>>
>>> For cheap excuses why i915 is so crap in 4.2: Thanks to a hipshot decision
>>> to transition to a different QA team ("we'll do this in 1 week without
>>> upfront planing") I essentially don't have proper QA support for 1-2
>>> months by now. The other trouble in this area specifically is that this
>>> code is already completely changed in -next again, so any testing done on
>>> integration trees (like -next or drm-intel-nightly) won't test any patches
>>> for 4.2.
>>> -Daniel
>>>
>>> Oh and Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> in case you
>>> decide to apply this right away.
>>>
>> Well your version has the benefit of compiling without errors. :-)
>>
>> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Just noticed another problem:
> On each resume I get the following error:
> -----------[ cut here ]------------
> WARNING: CPU: 2 PID: 2663 at
> /data/kernel/linux/drivers/gpu/drm/i915/intel_display.c:6319
> 0xffffffff9a33d5e9()
> WARN_ON(!crtc->state->enable)
> CPU: 2 PID: 2663 Comm: kworker/u8:80 Not tainted 4.2.0-rc2 #15
> ardware name: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
> orkqueue: events_unbound 0xffffffff9a055750
> 0000000000000000 ffffffff9a98ea28 ffffffff9a6d84d2 0000000000000000
> ffffffff9a03c416 ffff88020951c4e0 0000000000000000 0000000000000000
> ffff8802141cb800 ffff88021630c000 ffffffff9a03c4d5 ffffffff9a9c3664
> all Trace:
> [<ffffffff9a6d84d2>] ? 0xffffffff9a6d84d2
> [<ffffffff9a03c416>] ? 0xffffffff9a03c416
> [<ffffffff9a03c4d5>] ? 0xffffffff9a03c4d5
> [<ffffffff9a33d5e9>] ? 0xffffffff9a33d5e9
> [<ffffffff9a343ac3>] ? 0xffffffff9a343ac3
> [<ffffffff9a34444a>] ? 0xffffffff9a34444a
> [<ffffffff9a345518>] ? 0xffffffff9a345518
> [<ffffffff9a3246f0>] ? 0xffffffff9a3246f0
> [<ffffffff9a2e1ce8>] ? 0xffffffff9a2e1ce8
> [<ffffffff9a236170>] ? 0xffffffff9a236170
> [<ffffffff9a38b28d>] ? 0xffffffff9a38b28d
> [<ffffffff9a38b784>] ? 0xffffffff9a38b784
> [<ffffffff9a38baa4>] ? 0xffffffff9a38baa4
> [<ffffffff9a05577d>] ? 0xffffffff9a05577d
> [<ffffffff9a04dc47>] ? 0xffffffff9a04dc47
> [<ffffffff9a04dfab>] ? 0xffffffff9a04dfab
> [<ffffffff9a04dea0>] ? 0xffffffff9a04dea0
> [<ffffffff9a05331c>] ? 0xffffffff9a05331c
> [<ffffffff9a053260>] ? 0xffffffff9a053260
> [<ffffffff9a6dfa0f>] ? 0xffffffff9a6dfa0f
> [<ffffffff9a053260>] ? 0xffffffff9a053260
> --[ end trace 1b6d28ee34071679 ]---
>
> Nervertheless resume works, so it doesn't hurt me.
>
>
> BTW: I get also up to 40..50!  compile warnings like:
> i915/i915_drv.h: In function 'i915_debugfs_connector_add':
> i915/i915_drv.h:3119:53: warning: no return statement in function
> returning non-void [-Wreturn-type]
>
> which may cause yet uncovered troubles.
>
> Thanks, Jörg
kallsyms please!

Looks like intel_crtc_disable being called with a mode change on a already disabled crtc, it's gone in 4.3 because of the atomic rework.

Does something like below work?

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index ba9321998a41..725d2b727704 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6315,9 +6315,6 @@ static void intel_crtc_disable(struct drm_crtc *crtc)
 	struct drm_connector *connector;
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	/* crtc should still be enabled when we disable it. */
-	WARN_ON(!crtc->state->enable);
-
 	intel_crtc_disable_planes(crtc);
 	dev_priv->display.crtc_disable(crtc);
 	dev_priv->display.off(crtc);
@@ -12591,7 +12588,8 @@ static int __intel_set_mode(struct drm_crtc *modeset_crtc,
 			continue;
 
 		if (!crtc_state->enable) {
-			intel_crtc_disable(crtc);
+			if (crtc->state->enable)
+				intel_crtc_disable(crtc);
 		} else if (crtc->state->enable) {
 			intel_crtc_disable_planes(crtc);
 			dev_priv->display.crtc_disable(crtc);

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#1182609

FromJörg Otte <jrg.otte@gmail.com>
Date2015-07-13 11:00 +0200
Message-ID<pLHKH-2Sb-11@gated-at.bofh.it>
In reply to#1182575
2015-07-13 9:58 GMT+02:00 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
> Op 13-07-15 om 09:42 schreef Jörg Otte:
>> 2015-07-13 9:23 GMT+02:00 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>:
>>> Op 13-07-15 om 08:22 schreef Daniel Vetter:
>>>> On Sun, Jul 12, 2015 at 09:52:51AM -0700, Linus Torvalds wrote:
>>>>> On Sun, Jul 12, 2015 at 1:03 AM, Jörg Otte <jrg.otte@gmail.com> wrote:
>>>>>> BUG: unable to handle kernel NULL pointer dereference at 0000000000000009
>>>>>> IP: [<ffffffffbd3447bb>] 0xffffffffbd3447bb
>>>>> Ugh. Please enable KALLSYMS to get sane symbols.
>>>>>
>>>>> But yes, "crtc_state->base.active" is at offset 9 from "crtc_state",
>>>>> so it's pretty clearly just that change frm
>>>>>
>>>>> -       if (intel_crtc->active) {
>>>>> +       if (crtc_state->base.active) {
>>>>>
>>>>> and "crtc_state" is NULL.
>>>>>
>>>>> And the code very much knows that crtc_state can be NULL, since it's
>>>>> initialized with
>>>>>
>>>>>         crtc_state = state->base.state ?
>>>>>                 intel_atomic_get_crtc_state(state->base.state,
>>>>> intel_crtc) : NULL;
>>>>>
>>>>> Tssk. Daniel? Should I just revert that commit dec4f799d0a4
>>>>> ("drm/i915: Use crtc_state->active in primary check_plane func") for
>>>>> now, or is there a better fix? Like just checking crtc_state for NULL?
>>>> Indeed embarrassing. I've missed that we still have 1 caller left that's
>>>> using the transitional helpers, and those don't fill out
>>>> plane_state->state backpointers to the global atomic update since there is
>>>> no global atomic update for transitional helpers. Below diff should fix
>>>> this - we need to preferentially check crts_state->active and if that's
>>>> not set intel_crtc->active should yield the right result for the one
>>>> remaining caller (it's in the crtc_disable paths).
>>>>
>>>> For cheap excuses why i915 is so crap in 4.2: Thanks to a hipshot decision
>>>> to transition to a different QA team ("we'll do this in 1 week without
>>>> upfront planing") I essentially don't have proper QA support for 1-2
>>>> months by now. The other trouble in this area specifically is that this
>>>> code is already completely changed in -next again, so any testing done on
>>>> integration trees (like -next or drm-intel-nightly) won't test any patches
>>>> for 4.2.
>>>> -Daniel
>>>>
>>>> Oh and Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> in case you
>>>> decide to apply this right away.
>>>>
>>> Well your version has the benefit of compiling without errors. :-)
>>>
>>> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Just noticed another problem:
>> On each resume I get the following error:
>> -----------[ cut here ]------------
>> WARNING: CPU: 2 PID: 2663 at
>> /data/kernel/linux/drivers/gpu/drm/i915/intel_display.c:6319
>> 0xffffffff9a33d5e9()
>> WARN_ON(!crtc->state->enable)
>> CPU: 2 PID: 2663 Comm: kworker/u8:80 Not tainted 4.2.0-rc2 #15
>> ardware name: FUJITSU LIFEBOOK AH532/FJNBB1C, BIOS Version 1.09 05/22/2012
>> orkqueue: events_unbound 0xffffffff9a055750
>> 0000000000000000 ffffffff9a98ea28 ffffffff9a6d84d2 0000000000000000
>> ffffffff9a03c416 ffff88020951c4e0 0000000000000000 0000000000000000
>> ffff8802141cb800 ffff88021630c000 ffffffff9a03c4d5 ffffffff9a9c3664
>> all Trace:
>> [<ffffffff9a6d84d2>] ? 0xffffffff9a6d84d2
>> [<ffffffff9a03c416>] ? 0xffffffff9a03c416
>> [<ffffffff9a03c4d5>] ? 0xffffffff9a03c4d5
>> [<ffffffff9a33d5e9>] ? 0xffffffff9a33d5e9
>> [<ffffffff9a343ac3>] ? 0xffffffff9a343ac3
>> [<ffffffff9a34444a>] ? 0xffffffff9a34444a
>> [<ffffffff9a345518>] ? 0xffffffff9a345518
>> [<ffffffff9a3246f0>] ? 0xffffffff9a3246f0
>> [<ffffffff9a2e1ce8>] ? 0xffffffff9a2e1ce8
>> [<ffffffff9a236170>] ? 0xffffffff9a236170
>> [<ffffffff9a38b28d>] ? 0xffffffff9a38b28d
>> [<ffffffff9a38b784>] ? 0xffffffff9a38b784
>> [<ffffffff9a38baa4>] ? 0xffffffff9a38baa4
>> [<ffffffff9a05577d>] ? 0xffffffff9a05577d
>> [<ffffffff9a04dc47>] ? 0xffffffff9a04dc47
>> [<ffffffff9a04dfab>] ? 0xffffffff9a04dfab
>> [<ffffffff9a04dea0>] ? 0xffffffff9a04dea0
>> [<ffffffff9a05331c>] ? 0xffffffff9a05331c
>> [<ffffffff9a053260>] ? 0xffffffff9a053260
>> [<ffffffff9a6dfa0f>] ? 0xffffffff9a6dfa0f
>> [<ffffffff9a053260>] ? 0xffffffff9a053260
>> --[ end trace 1b6d28ee34071679 ]---
>>
>> Nervertheless resume works, so it doesn't hurt me.
>>
>>
>> BTW: I get also up to 40..50!  compile warnings like:
>> i915/i915_drv.h: In function 'i915_debugfs_connector_add':
>> i915/i915_drv.h:3119:53: warning: no return statement in function
>> returning non-void [-Wreturn-type]
>>
>> which may cause yet uncovered troubles.
>>
>> Thanks, Jörg
> kallsyms please!
>
> Looks like intel_crtc_disable being called with a mode change on a already disabled crtc, it's gone in 4.3 because of the atomic rework.
>
> Does something like below work?
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index ba9321998a41..725d2b727704 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -6315,9 +6315,6 @@ static void intel_crtc_disable(struct drm_crtc *crtc)
>         struct drm_connector *connector;
>         struct drm_i915_private *dev_priv = dev->dev_private;
>
> -       /* crtc should still be enabled when we disable it. */
> -       WARN_ON(!crtc->state->enable);
> -
>         intel_crtc_disable_planes(crtc);
>         dev_priv->display.crtc_disable(crtc);
>         dev_priv->display.off(crtc);
> @@ -12591,7 +12588,8 @@ static int __intel_set_mode(struct drm_crtc *modeset_crtc,
>                         continue;
>
>                 if (!crtc_state->enable) {
> -                       intel_crtc_disable(crtc);
> +                       if (crtc->state->enable)
> +                               intel_crtc_disable(crtc);
>                 } else if (crtc->state->enable) {
>                         intel_crtc_disable_planes(crtc);
>                         dev_priv->display.crtc_disable(crtc);
>
The patch works for me.

Thanks, Jörg
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