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<p>I was able to reproduce the crash by using the attached
simulate_crash.patch - waiting on guilty job to signal in reset
work and artificially rearming the timeout timer just before the
check for !cancel_delayed_work(&sched->work_tdr) in
drm_sched_cleanup_jobs - crash log attached in crash.log. This I
think confirms my theory i described earlier in this thread.</p>
<p>basic_fix.patch handles this by testing whether another timer
already armed ob this scheduler or is there a timeout work in
execution right now (see documentation for work_busy) - obviously
this is not a full solution as this will not protect from races if
for example there is immediate work scheduling such as in <font size="2" face="Calibri"><span style="font-size:11pt;">drm_sched_fault
- so we probably need to account for this by making
drm_sched_cleanup_jobs (at least in the part where it iterates
ring mirror list and frees jobs) and GPU reset really mutually
exclusive and not like now.</span></font></p>
<p><font size="2" face="Calibri"><span style="font-size:11pt;">Andrey<br>
</span></font></p>
<p><br>
</p>
<div class="moz-cite-prefix">On 11/11/19 4:11 PM, Christian König
wrote:<br>
</div>
<blockquote type="cite" cite="mid:2f035f22-4057-dd9e-27ef-0f5612113e29@amd.com">
<div class="moz-cite-prefix">Hi Emily,<br>
<br>
you need to print which scheduler instance is freeing the jobs
and which one is triggering the reset. The TID and PID is
completely meaningless here since we are called from different
worker threads and the TID/PID can change on each call.<br>
<br>
Apart from that I will look into this a bit deeper when I have
time.<br>
<br>
Regards,<br>
Christian.<br>
<br>
Am 12.11.19 um 07:02 schrieb Deng, Emily:<br>
</div>
<blockquote type="cite" cite="mid:MN2PR12MB29750EDB35E27DF9CD63152C8F770@MN2PR12MB2975.namprd12.prod.outlook.com">
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<font size="2" face="Calibri"><span style="font-size:11pt;">
<div>Hi Christian,</div>
<div> I add the follow print in function
drm_sched_cleanup_jobs. From the log it shows that only
use cancel_delayed_work could not avoid to free job when
the sched is in reset. But don’t know exactly where it is
wrong about the driver. Do you have any suggestion about
this?</div>
<div><font face="Times New Roman"> </font></div>
<div>+
printk("Emily:drm_sched_cleanup_jobs:begin,tid:%lu,
pid:%lu\n", current->tgid, current->pid);</div>
<div> </div>
<div> /*</div>
<div> * Don't destroy jobs while the timeout worker
is running OR thread</div>
<div> * is being parked and hence assumed to not
touch ring_mirror_list</div>
<div> */</div>
<div> if ((sched->timeout != MAX_SCHEDULE_TIMEOUT
&&</div>
<div>
!cancel_delayed_work(&sched->work_tdr)))</div>
<div> return;</div>
<div>+ printk("Emily:drm_sched_cleanup_jobs,tid:%lu,
pid:%lu\n", current->tgid, current->pid);</div>
<div><font face="Times New Roman"> </font></div>
<div><font face="Times New Roman"> </font></div>
<div><font face="Calibri">Best wishes</font></div>
<div><font face="Calibri">Emily Deng</font></div>
<div><font face="Times New Roman"> </font></div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11380.695091]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11380.695104]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11380.695105]
Emily:drm_sched_cleanup_jobs,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11380.695107]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11380.695107]
Emily:drm_sched_cleanup_jobs,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.222954] [drm:amdgpu_job_timedout [amdgpu]]
*ERROR* ring sdma0 timeout, signaled seq=78585, emitted
seq=78587</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.224275] [drm:amdgpu_job_timedout [amdgpu]]
*ERROR* Process information: process pid 0 thread pid 0,
s_job:00000000fe75ab36,tid=15603, pid=15603</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225413] amdgpu 0000:00:08.0: <font color="#00B050">GPU reset begin</font>!</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225417]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225425]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225425]
Emily:drm_sched_cleanup_jobs,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225428] Emily:<font color="#00B050">amdgpu_job_free_cb</font>,Process
information: process pid 0 thread pid 0,
s_job:00000000fe75ab36, tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225429]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225430]
Emily:drm_sched_cleanup_jobs,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225473]
Emily:drm_sched_cleanup_jobs:begin,tid:2253, pid:2253</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225486]
Emily:drm_sched_cleanup_jobs:begin,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225489]
Emily:drm_sched_cleanup_jobs,tid:2262, pid:2262</div>
<div>Nov 12 12:58:20 ubuntu-drop-August-2018-rc2-gpu0-vf02
kernel: [11381.225494] Emily:amdgpu_job_free_cb,Process
information: process pid 0 thread pid 0,
s_job:00000000f086ec84, tid:2262, pid:2262</div>
<div>>-----Original Message-----</div>
<div>>From: Grodzovsky, Andrey <a class="moz-txt-link-rfc2396E" href="mailto:Andrey.Grodzovsky@amd.com" moz-do-not-send="true"><Andrey.Grodzovsky@amd.com></a></div>
<div>>Sent: Tuesday, November 12, 2019 11:28 AM</div>
<div>>To: Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a>;
Deng, Emily</div>
<div>><a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>>Subject: Re: [PATCH] drm/amdgpu: Fix the null
pointer issue for tdr</div>
<div>></div>
<div>>Thinking more about this claim - we assume here
that if cancel_delayed_work</div>
<div>>returned true it guarantees that timeout work is
not running but, it merely</div>
<div>>means there was a pending timeout work which was
removed from the</div>
<div>>workqueue before it's timer elapsed and so it
didn't have a chance to be</div>
<div>>dequeued and executed, it doesn't cover already
executing work. So there is a</div>
<div>>possibility where while timeout work started
executing another timeout work</div>
<div>>already got enqueued (maybe through earlier cleanup
jobs or through</div>
<div>>drm_sched_fault) and if at this point another
drm_sched_cleanup_jobs runs</div>
<div>>cancel_delayed_work(&sched->work_tdr) will
return true even while there is a</div>
<div>>timeout job in progress.</div>
<div>>Unfortunately we cannot change cancel_delayed_work
to</div>
<div>>cancel_delayed_work_sync to flush the timeout work
as timeout work itself</div>
<div>>waits for schedule thread to be parked again when
calling park_thread.</div>
<div>></div>
<div>>Andrey</div>
<div>></div>
<div>>________________________________________</div>
<div>>From: amd-gfx <a class="moz-txt-link-rfc2396E" href="mailto:amd-gfx-bounces@lists.freedesktop.org" moz-do-not-send="true"><amd-gfx-bounces@lists.freedesktop.org></a>
on behalf of</div>
<div>>Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a></div>
<div>>Sent: 08 November 2019 05:35:18</div>
<div>>To: Deng, Emily; <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>>Subject: Re: [PATCH] drm/amdgpu: Fix the null
pointer issue for tdr</div>
<div>></div>
<div>>Hi Emily,</div>
<div>></div>
<div>>exactly that can't happen. See here:</div>
<div>></div>
<div>>> /* Don't destroy jobs while the
timeout worker is running */</div>
<div>>> if (sched->timeout !=
MAX_SCHEDULE_TIMEOUT &&</div>
<div>>>
!cancel_delayed_work(&sched->work_tdr))</div>
<div>>> return NULL;</div>
<div>></div>
<div>>We never free jobs while the timeout working is
running to prevent exactly</div>
<div>>that issue.</div>
<div>></div>
<div>>Regards,</div>
<div>>Christian.</div>
<div>></div>
<div>>Am 08.11.19 um 11:32 schrieb Deng, Emily:</div>
<div>>> Hi Christian,</div>
<div>>> The drm_sched_job_timedout->
amdgpu_job_timedout call</div>
<div>>amdgpu_device_gpu_recover. I mean the main
scheduler free the jobs while</div>
<div>>in amdgpu_device_gpu_recover, and before calling
drm_sched_stop.</div>
<div>>></div>
<div>>> Best wishes</div>
<div>>> Emily Deng</div>
<div>>></div>
<div>>></div>
<div>>></div>
<div>>>> -----Original Message-----</div>
<div>>>> From: Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a></div>
<div>>>> Sent: Friday, November 8, 2019 6:26 PM</div>
<div>>>> To: Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>>>> Subject: Re: [PATCH] drm/amdgpu: Fix the
null pointer issue for tdr</div>
<div>>>></div>
<div>>>> Hi Emily,</div>
<div>>>></div>
<div>>>> well who is calling
amdgpu_device_gpu_recover() in this case?</div>
<div>>>></div>
<div>>>> When it's not the scheduler we shouldn't
have a guilty job in the first place.</div>
<div>>>></div>
<div>>>> Regards,</div>
<div>>>> Christian.</div>
<div>>>></div>
<div>>>> Am 08.11.19 um 11:22 schrieb Deng, Emily:</div>
<div>>>>> Hi Chrisitan,</div>
<div>>>>> No, I am with the new branch
and also has the patch. Even it</div>
<div>>>>> are freed by</div>
<div>>>> main scheduler, how we could avoid main
scheduler to free jobs while</div>
<div>>>> enter to function
amdgpu_device_gpu_recover?</div>
<div>>>>> Best wishes</div>
<div>>>>> Emily Deng</div>
<div>>>>></div>
<div>>>>></div>
<div>>>>></div>
<div>>>>>> -----Original Message-----</div>
<div>>>>>> From: Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a></div>
<div>>>>>> Sent: Friday, November 8, 2019
6:15 PM</div>
<div>>>>>> To: Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;
amd-</div>
<div>><a class="moz-txt-link-abbreviated" href="mailto:gfx@lists.freedesktop.org" moz-do-not-send="true">gfx@lists.freedesktop.org</a></div>
<div>>>>>> Subject: Re: [PATCH] drm/amdgpu:
Fix the null pointer issue for tdr</div>
<div>>>>>></div>
<div>>>>>> Hi Emily,</div>
<div>>>>>></div>
<div>>>>>> in this case you are on an old
code branch.</div>
<div>>>>>></div>
<div>>>>>> Jobs are freed now by the main
scheduler thread and only if no</div>
<div>>>>>> timeout handler is running.</div>
<div>>>>>></div>
<div>>>>>> See this patch here:</div>
<div>>>>>>> commit
5918045c4ed492fb5813f980dcf89a90fefd0a4e</div>
<div>>>>>>> Author: Christian König <a class="moz-txt-link-rfc2396E" href="mailto:christian.koenig@amd.com" moz-do-not-send="true"><christian.koenig@amd.com></a></div>
<div>>>>>>> Date: Thu Apr 18 11:00:21
2019 -0400</div>
<div>>>>>>></div>
<div>>>>>>> drm/scheduler: rework
job destruction</div>
<div>>>>>> Regards,</div>
<div>>>>>> Christian.</div>
<div>>>>>></div>
<div>>>>>> Am 08.11.19 um 11:11 schrieb Deng,
Emily:</div>
<div>>>>>>> Hi Christian,</div>
<div>>>>>>> Please refer to follow
log, when it enter to</div>
<div>>>>>>> amdgpu_device_gpu_recover</div>
<div>>>>>> function, the bad job
000000005086879e is freeing in function</div>
<div>>>>>> amdgpu_job_free_cb at the same
time, because of the hardware fence</div>
<div>>>> signal.</div>
<div>>>>>> But amdgpu_device_gpu_recover goes
faster, at this case, the</div>
<div>>>>>> s_fence is already freed, but job
is not freed in time. Then this issue</div>
<div>>occurs.</div>
<div>>>>>>> [ 449.792189]
[drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring</div>
<div>>>> sdma0</div>
<div>>>>>>> timeout, signaled seq=2481,
emitted seq=2483 [ 449.793202]</div>
<div>>>>>>> [drm:amdgpu_job_timedout
[amdgpu]] *ERROR* Process information:</div>
<div>>>>>> process pid 0 thread pid 0,
s_job:000000005086879e [ 449.794163]</div>
<div>>>>>> amdgpu</div>
<div>>>>>> 0000:00:08.0: GPU reset begin!</div>
<div>>>>>>> [ 449.794175]
Emily:amdgpu_job_free_cb,Process information:</div>
<div>>>>>>> process pid 0 thread pid 0,
s_job:000000005086879e [ 449.794221]</div>
<div>>>>>>>
Emily:amdgpu_job_free_cb,Process information: process pid
0</div>
<div>>>>>>> thread pid 0,
s_job:0000000066eb74ab [ 449.794222]</div>
<div>>>>>>>
Emily:amdgpu_job_free_cb,Process information: process pid
0</div>
<div>>>>>>> thread pid 0,
s_job:00000000d4438ad9 [ 449.794255]</div>
<div>>>>>>>
Emily:amdgpu_job_free_cb,Process information: process pid
0</div>
<div>>>>>>> thread pid 0,
s_job:00000000b6d69c65 [ 449.794257]</div>
<div>>>>>>>
Emily:amdgpu_job_free_cb,Process information: process pid
0</div>
<div>>>>>>> thread pid 0,</div>
<div>>>>>> s_job:00000000ea85e922 [
449.794287]</div>
<div>>>>>> Emily:amdgpu_job_free_cb,Process</div>
<div>>>>>> information: process pid 0
thread pid 0, s_job:00000000ed3a5ac6 [</div>
<div>>>>>> 449.794366] BUG: unable to handle
kernel NULL pointer dereference</div>
<div>>>>>> at</div>
<div>>>>>> 00000000000000c0 [ 449.800818]
PGD 0 P4D 0 [ 449.801040] Oops:</div>
<div>>>>>> 0000 [#1] SMP PTI</div>
<div>>>>>>> [ 449.801338] CPU: 3 PID: 55
Comm: kworker/3:1 Tainted: G OE</div>
<div>>>>>> 4.18.0-15-generic
#16~18.04.1-Ubuntu</div>
<div>>>>>>> [ 449.802157] Hardware name:
QEMU Standard PC (i440FX + PIIX,</div>
<div>>>>>>> 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014 [ 449.802944]</div>
<div>>>>>>> Workqueue: events
drm_sched_job_timedout [amd_sched] [</div>
<div>>>>>>> 449.803488]</div>
<div>>>> RIP:</div>
<div>>>>>>
0010:amdgpu_device_gpu_recover+0x1da/0xb60 [amdgpu]</div>
<div>>>>>>> [ 449.804020] Code: dd ff ff
49 39 c5 48 89 55 a8 0f 85 56 ff ff</div>
<div>>>>>>> ff</div>
<div>>>>>>> 45 85 e4 0f</div>
<div>>>>>> 85 a1 00 00 00 48 8b 45 b0 48 85
c0 0f 84 60 01 00 00 48 8b 40 10</div>
<div>>>>>> <48> 8b</div>
<div>>>> 98</div>
<div>>>>>> c0 00 00 00 48 85 db 0f 84
4c 01 00 00 48 8b 43 48 a8 01</div>
<div>>>>>>> [ 449.805593] RSP:
0018:ffffb4c7c08f7d68 EFLAGS: 00010286 [</div>
<div>>>>>>> 449.806032] RAX:
0000000000000000 RBX: 0000000000000000 RCX:</div>
<div>>>>>>> 0000000000000000 [
449.806625] RDX: ffffb4c7c08f5ac0 RSI:</div>
<div>>>>>>> 0000000fffffffe0 RDI:
0000000000000246 [ 449.807224] RBP:</div>
<div>>>>>>> ffffb4c7c08f7de0 R08:
00000068b9d54000 R09: 0000000000000000 [</div>
<div>>>>>>> 449.807818] R10:
0000000000000000 R11: 0000000000000148 R12:</div>
<div>>>>>>> 0000000000000000 [
449.808411] R13: ffffb4c7c08f7da0 R14:</div>
<div>>>>>>> ffff8d82b8525d40 R15:
ffff8d82b8525d40 [ 449.809004] FS:</div>
<div>>>>>>> 0000000000000000(0000)
GS:ffff8d82bfd80000(0000)</div>
<div>>>>>>> knlGS:0000000000000000 [
449.809674] CS: 0010 DS: 0000 ES: 0000</div>
<div>>CR0:</div>
<div>>>>>>> 0000000080050033 [
449.810153] CR2: 00000000000000c0 CR3:</div>
<div>>>>>>> 000000003cc0a001 CR4:
00000000003606e0 [ 449.810747] DR0:</div>
<div>>>>>> 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000 [</div>
<div>>>>>> 449.811344] DR3: 0000000000000000
DR6: 00000000fffe0ff0 DR7:</div>
<div>>>>>> 0000000000000400 [ 449.811937]
Call Trace:</div>
<div>>>>>>> [ 449.812206]
amdgpu_job_timedout+0x114/0x140 [amdgpu] [</div>
<div>>>>>>> 449.812635]
drm_sched_job_timedout+0x44/0x90 [amd_sched] [</div>
<div>>>>>>> 449.813139] ?
amdgpu_cgs_destroy_device+0x10/0x10 [amdgpu] [</div>
<div>>>>>>> 449.813609] ?
drm_sched_job_timedout+0x44/0x90 [amd_sched] [</div>
<div>>>>>>> 449.814077]
process_one_work+0x1fd/0x3f0 [ 449.814417]</div>
<div>>>>>>> worker_thread+0x34/0x410 [
449.814728] kthread+0x121/0x140 [</div>
<div>>>>>>> 449.815004] ?
process_one_work+0x3f0/0x3f0 [ 449.815374] ?</div>
<div>>>>>>>
kthread_create_worker_on_cpu+0x70/0x70</div>
<div>>>>>>> [ 449.815799]
ret_from_fork+0x35/0x40</div>
<div>>>>>>></div>
<div>>>>>>>> -----Original Message-----</div>
<div>>>>>>>> From: Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a></div>
<div>>>>>>>> Sent: Friday, November 8,
2019 5:43 PM</div>
<div>>>>>>>> To: Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;
amd-</div>
<div>>>> <a class="moz-txt-link-abbreviated" href="mailto:gfx@lists.freedesktop.org" moz-do-not-send="true">gfx@lists.freedesktop.org</a></div>
<div>>>>>>>> Subject: Re: [PATCH]
drm/amdgpu: Fix the null pointer issue for</div>
<div>>>>>>>> tdr</div>
<div>>>>>>>></div>
<div>>>>>>>> Am 08.11.19 um 10:39
schrieb Deng, Emily:</div>
<div>>>>>>>>> Sorry, please take
your time.</div>
<div>>>>>>>> Have you seen my other
response a bit below?</div>
<div>>>>>>>></div>
<div>>>>>>>> I can't follow how it
would be possible for job->s_fence to be</div>
<div>>>>>>>> NULL without the job also
being freed.</div>
<div>>>>>>>></div>
<div>>>>>>>> So it looks like this
patch is just papering over some bigger issues.</div>
<div>>>>>>>></div>
<div>>>>>>>> Regards,</div>
<div>>>>>>>> Christian.</div>
<div>>>>>>>></div>
<div>>>>>>>>> Best wishes</div>
<div>>>>>>>>> Emily Deng</div>
<div>>>>>>>>></div>
<div>>>>>>>>></div>
<div>>>>>>>>></div>
<div>>>>>>>>>> -----Original
Message-----</div>
<div>>>>>>>>>> From: Koenig,
Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a></div>
<div>>>>>>>>>> Sent: Friday,
November 8, 2019 5:08 PM</div>
<div>>>>>>>>>> To: Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;
amd-</div>
<div>>>>>> <a class="moz-txt-link-abbreviated" href="mailto:gfx@lists.freedesktop.org" moz-do-not-send="true">gfx@lists.freedesktop.org</a></div>
<div>>>>>>>>>> Subject: Re:
[PATCH] drm/amdgpu: Fix the null pointer issue for</div>
<div>>>>>>>>>> tdr</div>
<div>>>>>>>>>></div>
<div>>>>>>>>>> Am 08.11.19 um
09:52 schrieb Deng, Emily:</div>
<div>>>>>>>>>>> Ping.....</div>
<div>>>>>>>>>> You need to give
me at least enough time to wake up :)</div>
<div>>>>>>>>>></div>
<div>>>>>>>>>>> Best wishes</div>
<div>>>>>>>>>>> Emily Deng</div>
<div>>>>>>>>>>></div>
<div>>>>>>>>>>></div>
<div>>>>>>>>>>></div>
<div>>>>>>>>>>>>
-----Original Message-----</div>
<div>>>>>>>>>>>> From:
amd-gfx <a class="moz-txt-link-rfc2396E" href="mailto:amd-gfx-bounces@lists.freedesktop.org" moz-do-not-send="true"><amd-gfx-bounces@lists.freedesktop.org></a>
On</div>
<div>>>> Behalf</div>
<div>>>>>>>>>>>> Of Deng,
Emily</div>
<div>>>>>>>>>>>> Sent:
Friday, November 8, 2019 10:56 AM</div>
<div>>>>>>>>>>>> To:
Koenig, Christian <a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com" moz-do-not-send="true"><Christian.Koenig@amd.com></a>;
amd-</div>
<div>>>>>>>>>>>> <a class="moz-txt-link-abbreviated" href="mailto:gfx@lists.freedesktop.org" moz-do-not-send="true">gfx@lists.freedesktop.org</a></div>
<div>>>>>>>>>>>> Subject:
RE: [PATCH] drm/amdgpu: Fix the null pointer issue</div>
<div>>>>>>>>>>>> for tdr</div>
<div>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>
-----Original Message-----</div>
<div>>>>>>>>>>>>> From:
Christian König <a class="moz-txt-link-rfc2396E" href="mailto:ckoenig.leichtzumerken@gmail.com" moz-do-not-send="true"><ckoenig.leichtzumerken@gmail.com></a></div>
<div>>>>>>>>>>>>> Sent:
Thursday, November 7, 2019 7:28 PM</div>
<div>>>>>>>>>>>>> To:
Deng, Emily <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a>;</div>
<div>>>>>>>>>>>>> <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>>>>>>>>>>>>>
Subject: Re: [PATCH] drm/amdgpu: Fix the null pointer
issue</div>
<div>>>>>>>>>>>>> for
tdr</div>
<div>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>> Am
07.11.19 um 11:25 schrieb Emily Deng:</div>
<div>>>>>>>>>>>>>>
When the job is already signaled, the s_fence is freed.</div>
<div>>>>>>>>>>>>>>
Then it will has null pointer in
amdgpu_device_gpu_recover.</div>
<div>>>>>>>>>>>>> NAK,
the s_fence is only set to NULL when the job is destroyed.</div>
<div>>>>>>>>>>>>> See
drm_sched_job_cleanup().</div>
<div>>>>>>>>>>>> I know it
is set to NULL in drm_sched_job_cleanup. But in one</div>
<div>>>>>>>>>>>> case, when
it enter into the amdgpu_device_gpu_recover, it</div>
<div>>>>>>>>>>>> already in
drm_sched_job_cleanup, and at this time, it will</div>
<div>>>>>>>>>>>> go to free</div>
<div>>>>>> job.</div>
<div>>>>>>>>>>>> But the
amdgpu_device_gpu_recover sometimes is faster. At</div>
<div>>>>>>>>>>>> that time,
job is not freed, but s_fence is already NULL.</div>
<div>>>>>>>>>> No, that case
can't happen. See here:</div>
<div>>>>>>>>>></div>
<div>>>>>>>>>>>
drm_sched_job_cleanup(s_job);</div>
<div>>>>>>>>>>></div>
<div>>>>>>>>>>>
amdgpu_ring_priority_put(ring, s_job->s_priority);</div>
<div>>>>>>>>>>>
dma_fence_put(job->fence);</div>
<div>>>>>>>>>>>
amdgpu_sync_free(&job->sync);</div>
<div>>>>>>>>>>>
amdgpu_sync_free(&job->sched_sync);</div>
<div>>>>>>>>>>>
kfree(job);</div>
<div>>>>>>>>>> The job itself is
freed up directly after freeing the reference</div>
<div>>>>>>>>>> to the</div>
<div>>>>>> s_fence.</div>
<div>>>>>>>>>> So you are just
papering over a much bigger problem here. This</div>
<div>>>>>>>>>> patch is a clear
NAK.</div>
<div>>>>>>>>>></div>
<div>>>>>>>>>> Regards,</div>
<div>>>>>>>>>> Christian.</div>
<div>>>>>>>>>></div>
<div>>>>>>>>>>>>> When
you see a job without an s_fence then that means the</div>
<div>>>>>>>>>>>>>
problem is somewhere else.</div>
<div>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>
Regards,</div>
<div>>>>>>>>>>>>>
Christian.</div>
<div>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>>
Signed-off-by: Emily Deng <a class="moz-txt-link-rfc2396E" href="mailto:Emily.Deng@amd.com" moz-do-not-send="true"><Emily.Deng@amd.com></a></div>
<div>>>>>>>>>>>>>>
---</div>
<div>>>>>>>>>>>>>>
drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-</div>
<div>>>>>>>>>>>>>>
drivers/gpu/drm/scheduler/sched_main.c | 11 ++++++---</div>
<div>>--</div>
<div>>>>>>>>>>>>>>
2 files changed, 7 insertions(+), 6 deletions(-)</div>
<div>>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c</div>
<div>>>>>>>>>>>>>>
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c</div>
<div>>>>>>>>>>>>>>
index e6ce949..5a8f08e 100644</div>
<div>>>>>>>>>>>>>>
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c</div>
<div>>>>>>>>>>>>>>
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c</div>
<div>>>>>>>>>>>>>> @@
-4075,7 +4075,7 @@ int</div>
<div>>>> amdgpu_device_gpu_recover(struct</div>
<div>>>>>>>>>>>>>
amdgpu_device *adev,</div>
<div>>>>>>>>>>>>>>
*</div>
<div>>>>>>>>>>>>>>
* job->base holds a reference to parent fence</div>
<div>>>>>>>>>>>>>>
*/</div>
<div>>>>>>>>>>>>>> -
if (job && job->base.s_fence->parent
&&</div>
<div>>>>>>>>>>>>>> +
if (job && job->base.s_fence &&</div>
<div>>>>>>>>>>>>>> +
job->base.s_fence->parent</div>
<div>>>>>>>> &&</div>
<div>>>>>>>>>>>>>>
dma_fence_is_signaled(job->base.s_fence->parent))</div>
<div>>>>>>>>>>>>>>
job_signaled = true;</div>
<div>>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>>
diff --git a/drivers/gpu/drm/scheduler/sched_main.c</div>
<div>>>>>>>>>>>>>>
b/drivers/gpu/drm/scheduler/sched_main.c</div>
<div>>>>>>>>>>>>>>
index 31809ca..56cc10e 100644</div>
<div>>>>>>>>>>>>>>
--- a/drivers/gpu/drm/scheduler/sched_main.c</div>
<div>>>>>>>>>>>>>>
+++ b/drivers/gpu/drm/scheduler/sched_main.c</div>
<div>>>>>>>>>>>>>> @@
-334,8 +334,8 @@ void</div>
<div>>drm_sched_increase_karma(struct</div>
<div>>>>>>>>>>>>>
drm_sched_job</div>
<div>>>>>>>>>>>>>>
*bad)</div>
<div>>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>>
spin_lock(&rq->lock);</div>
<div>>>>>>>>>>>>>>
list_for_each_entry_safe(entity,</div>
<div>>>>>>>>>>>>>>
tmp,</div>
<div>>>> &rq-</div>
<div>>>>>>>>> entities,</div>
<div>>>>>>>>>>>>> list)
{</div>
<div>>>>>>>>>>>>>>
- if
(bad->s_fence->scheduled.context</div>
<div>>>>>>>> ==</div>
<div>>>>>>>>>>>>>>
- entity->fence_context) {</div>
<div>>>>>>>>>>>>>>
+ if (bad->s_fence &&</div>
<div>>>>>>>>>>>>>> +
(bad->s_fence-</div>
<div>>>>>>>>>>>>>>
scheduled.context ==</div>
<div>>>>>>>>>>>>>>
+ entity->fence_context))
{</div>
<div>>>>>>>>>>>>>>
if</div>
<div>>>>>>>>>>>>>>
(atomic_read(&bad-</div>
<div>>>>>>>>> karma) ></div>
<div>>>>>>>>>>>>>>
bad->sched-</div>
<div>>>>> hang_limit)</div>
<div>>>>>>>>>>>>>>
if</div>
<div>>>>>>>>>>>>>>
(entity-</div>
<div>>>>> guilty) @@ -376,7 +376,7 @@ void</div>
<div>>>>>>>>>>>>>>
drm_sched_stop(struct</div>
<div>>>>>>>> drm_gpu_scheduler</div>
<div>>>>>>>>>>>>>
*sched, struct drm_sched_job *bad)</div>
<div>>>>>>>>>>>>>>
* This iteration is thread safe as sched thread</div>
<div>>>>>>>>>>>>>> is</div>
<div>>>> stopped.</div>
<div>>>>>>>>>>>>>>
*/</div>
<div>>>>>>>>>>>>>>
list_for_each_entry_safe_reverse(s_job, tmp,</div>
<div>>>>>>>>>>>>>>
&sched- ring_mirror_list, node) {</div>
<div>>>>>>>>>>>>>>
- if (s_job->s_fence->parent &&</div>
<div>>>>>>>>>>>>>>
+ if (s_job->s_fence &&
s_job->s_fence->parent &&</div>
<div>>>>>>>>>>>>>>
dma_fence_remove_callback(s_job-</div>
<div>>>>> s_fence-</div>
<div>>>>>>>>> parent,</div>
<div>>>>>>>>>>>>>>
&s_job->cb)) {</div>
<div>>>>>>>>>>>>>>
atomic_dec(&sched->hw_rq_count);</div>
<div>>>> @@ -</div>
<div>>>>>>>> 395,7</div>
<div>>>>>>>>>>>> +395,8 @@
void</div>
<div>>>>>>>>>>>>>>
drm_sched_stop(struct drm_gpu_scheduler</div>
<div>>>>>>>>>>>>>
*sched, struct drm_sched_job *bad)</div>
<div>>>>>>>>>>>>>>
*</div>
<div>>>>>>>>>>>>>>
* Job is still alive so fence</div>
<div>>>>>>>>>>>>>>
refcount at</div>
<div>>>> least 1</div>
<div>>>>>>>>>>>>>>
*/</div>
<div>>>>>>>>>>>>>>
-
dma_fence_wait(&s_job->s_fence->finished,</div>
<div>>>>>>>> false);</div>
<div>>>>>>>>>>>>>>
+ if (s_job->s_fence)</div>
<div>>>>>>>>>>>>>>
+
dma_fence_wait(&s_job->s_fence-</div>
<div>>>>>>>>> finished,</div>
<div>>>>>>>>>>>>>
false);</div>
<div>>>>>>>>>>>>>>
/*</div>
<div>>>>>>>>>>>>>>
* We must keep bad job alive</div>
<div>>>>>>>>>>>>>>
for later</div>
<div>>>> use</div>
<div>>>>>>>> during @@</div>
<div>>>>>>>>>>>>> -438,7</div>
<div>>>>>>>>>>>>>>
+439,7 @@ void drm_sched_start(struct drm_gpu_scheduler</div>
<div>>>>>> *sched,</div>
<div>>>>>>>>>>>>>>
+bool</div>
<div>>>>>>>>>>>>>
full_recovery)</div>
<div>>>>>>>>>>>>>>
* GPU recovers can't run in parallel.</div>
<div>>>>>>>>>>>>>>
*/</div>
<div>>>>>>>>>>>>>>
list_for_each_entry_safe(s_job, tmp,</div>
<div>>>>>>>>>>>>>>
&sched->ring_mirror_list,</div>
<div>>>>>>>>>>>>>>
node)</div>
<div>>>>>>>>>>>>> {</div>
<div>>>>>>>>>>>>>>
- struct dma_fence *fence =
s_job->s_fence->parent;</div>
<div>>>>>>>>>>>>>>
+ struct dma_fence *fence = s_job->s_fence ?</div>
<div>>>>>>>>>>>>>> +
s_job-</div>
<div>>>>>>>>> s_fence-</div>
<div>>>>>>>>>>>>>>
parent :</div>
<div>>>>>>>>>>>>>>
+NULL;</div>
<div>>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>>>
atomic_inc(&sched->hw_rq_count);</div>
<div>>>>>>>>>>>>>></div>
<div>>>>>>>>>>>>
_______________________________________________</div>
<div>>>>>>>>>>>> amd-gfx
mailing list</div>
<div>>>>>>>>>>>> <a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>>>>>>>>>>>> <a href="https://lists.freedesktop.org/mailman/listinfo/amd-gfx" moz-do-not-send="true">
https://lists.freedesktop.org/mailman/listinfo/amd-gfx</a></div>
<div>></div>
<div>>_______________________________________________</div>
<div>>amd-gfx mailing list</div>
<div>><a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org" moz-do-not-send="true">amd-gfx@lists.freedesktop.org</a></div>
<div>><a href="https://lists.freedesktop.org/mailman/listinfo/amd-gfx" moz-do-not-send="true">https://lists.freedesktop.org/mailman/listinfo/amd-gfx</a></div>
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