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<div class="moz-cite-prefix">On 1/19/21 11:39 AM, Chen, Horace
wrote:<br>
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<blockquote type="cite" cite="mid:CY4PR12MB157352A2F7BF029B68A4A769E1A30@CY4PR12MB1573.namprd12.prod.outlook.com">
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[AMD Official Use Only - Internal Distribution Only]<br>
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Hi Andrey,</div>
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<br>
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I think the list in the XGMI hive won't be break in the middle
if we lock the device before we change the list. Because if 2
devices in 1 hive went into the function, it will follow the
same sequence to lock the devices. So one of them will
definately break at the first device. I add iterate devices
here is just to lock all device in the hive since we will
change the device sequence in the hive soon after.</div>
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</blockquote>
<p><br>
</p>
<p>I didn't mean break in a sense of breaking the list itself, I
just meant the literal 'break' instruction<br>
to terminate the iteration once you failed to lock a particular
device. <br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CY4PR12MB157352A2F7BF029B68A4A769E1A30@CY4PR12MB1573.namprd12.prod.outlook.com">
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<br>
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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The reason to break the interation in the middle is that the
list is changed during the iteration without taking any lock.
It is quite bad since I'm fixing one of this issue. And for
XGMI hive, there are 2 locks protecting the list, one is the
device lock I changed here, the other one is in front of my
change, there is a hive->lock to protect the hive.</div>
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<br>
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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Even the bad thing really happened, I think moving back
through the list is also very dengerous since we don't know
what the list finally be, Unless we stack the devices we have
iterated through a mirrored list. That can be a big change.<br>
</div>
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</blockquote>
<p><br>
</p>
<p>Not sure we are on the same page, my concern is let's sat your
XGMI hive consists of 2 devices, you manged to call successfully
do<font size="2"><span style="font-size:11pt"><br>
amdgpu_device_lock_adev for dev1 but then failed for dev2, in
this case you will bail out </span></font> without releasing
dev1, no ?</p>
<p><br>
</p>
<p>Andrey<br>
</p>
<p><br>
</p>
<blockquote type="cite" cite="mid:CY4PR12MB157352A2F7BF029B68A4A769E1A30@CY4PR12MB1573.namprd12.prod.outlook.com">
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<br>
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<br>
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
I'm ok to seperate the locking in <font size="2"><span style="font-size:11pt">amdgpu_device_lock_adev here, I'll
do some test and update the code later.<br>
</span></font></div>
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font-size: 12pt; color: rgb(0, 0, 0);">
<font size="2"><span style="font-size:11pt"><br>
</span></font></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<font size="2"><span style="font-size:11pt">Thanks &
Regards,</span></font></div>
<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
font-size: 12pt; color: rgb(0, 0, 0);">
<font size="2"><span style="font-size:11pt">Horace.</span></font><br>
</div>
<div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>发件人:</b>
Grodzovsky, Andrey <a class="moz-txt-link-rfc2396E" href="mailto:Andrey.Grodzovsky@amd.com"><Andrey.Grodzovsky@amd.com></a><br>
<b>发送时间:</b> 2021年1月19日 22:33<br>
<b>收件人:</b> Chen, Horace <a class="moz-txt-link-rfc2396E" href="mailto:Horace.Chen@amd.com"><Horace.Chen@amd.com></a>;
<a class="moz-txt-link-abbreviated" href="mailto:amd-gfx@lists.freedesktop.org">amd-gfx@lists.freedesktop.org</a>
<a class="moz-txt-link-rfc2396E" href="mailto:amd-gfx@lists.freedesktop.org"><amd-gfx@lists.freedesktop.org></a><br>
<b>抄送:</b> Quan, Evan <a class="moz-txt-link-rfc2396E" href="mailto:Evan.Quan@amd.com"><Evan.Quan@amd.com></a>; Tuikov,
Luben <a class="moz-txt-link-rfc2396E" href="mailto:Luben.Tuikov@amd.com"><Luben.Tuikov@amd.com></a>; Koenig, Christian
<a class="moz-txt-link-rfc2396E" href="mailto:Christian.Koenig@amd.com"><Christian.Koenig@amd.com></a>; Deucher, Alexander
<a class="moz-txt-link-rfc2396E" href="mailto:Alexander.Deucher@amd.com"><Alexander.Deucher@amd.com></a>; Xiao, Jack
<a class="moz-txt-link-rfc2396E" href="mailto:Jack.Xiao@amd.com"><Jack.Xiao@amd.com></a>; Zhang, Hawking
<a class="moz-txt-link-rfc2396E" href="mailto:Hawking.Zhang@amd.com"><Hawking.Zhang@amd.com></a>; Liu, Monk
<a class="moz-txt-link-rfc2396E" href="mailto:Monk.Liu@amd.com"><Monk.Liu@amd.com></a>; Xu, Feifei
<a class="moz-txt-link-rfc2396E" href="mailto:Feifei.Xu@amd.com"><Feifei.Xu@amd.com></a>; Wang, Kevin(Yang)
<a class="moz-txt-link-rfc2396E" href="mailto:Kevin1.Wang@amd.com"><Kevin1.Wang@amd.com></a>; Xiaojie Yuan
<a class="moz-txt-link-rfc2396E" href="mailto:xiaojie.yuan@amd.com"><xiaojie.yuan@amd.com></a><br>
<b>主题:</b> Re: [PATCH 1/2] drm/amdgpu: race issue when
jobs on 2 ring timeout</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt">
<div class="PlainText"><br>
On 1/19/21 7:22 AM, Horace Chen wrote:<br>
> Fix a racing issue when jobs on 2 rings timeout
simultaneously.<br>
><br>
> If 2 rings timed out at the same time, the
amdgpu_device_gpu_recover<br>
> will be reentered. Then the
adev->gmc.xgmi.head will be grabbed<br>
> by 2 local linked list, which may cause wild
pointer issue in<br>
> iterating.<br>
><br>
> lock the device earily to prevent the node be
added to 2 different<br>
> lists.<br>
><br>
> Signed-off-by: Horace Chen
<a class="moz-txt-link-rfc2396E" href="mailto:horace.chen@amd.com"><horace.chen@amd.com></a><br>
> ---<br>
> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 42
+++++++++++++++-------<br>
> 1 file changed, 30 insertions(+), 12
deletions(-)<br>
><br>
> diff --git
a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> index 4d434803fb49..9574da3abc32 100644<br>
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c<br>
> @@ -4540,6 +4540,7 @@ int
amdgpu_device_gpu_recover(struct amdgpu_device *adev,<br>
> int i, r = 0;<br>
> bool need_emergency_restart = false;<br>
> bool audio_suspended = false;<br>
> + bool get_dev_lock = false;<br>
> <br>
> /*<br>
> * Special case: RAS triggered and full
reset isn't supported<br>
> @@ -4582,28 +4583,45 @@ int
amdgpu_device_gpu_recover(struct amdgpu_device *adev,<br>
> * Build list of devices to reset.<br>
> * In case we are in XGMI hive mode,
resort the device list<br>
> * to put adev in the 1st position.<br>
> + *<br>
> + * lock the device before we try to operate
the linked list<br>
> + * if didn't get the device lock, don't
touch the linked list since<br>
> + * others may iterating it.<br>
> */<br>
> INIT_LIST_HEAD(&device_list);<br>
> if (adev->gmc.xgmi.num_physical_nodes
> 1) {<br>
> if (!hive)<br>
> return -ENODEV;<br>
> - if
(!list_is_first(&adev->gmc.xgmi.head,
&hive->device_list))<br>
> -
list_rotate_to_front(&adev->gmc.xgmi.head,
&hive->device_list);<br>
> - device_list_handle =
&hive->device_list;<br>
> +<br>
> + list_for_each_entry(tmp_adev,
&hive->device_list, gmc.xgmi.head) {<br>
> + get_dev_lock =
amdgpu_device_lock_adev(tmp_adev, hive);<br>
> + if (!get_dev_lock)<br>
> + break;<br>
<br>
<br>
What about unlocking back all the devices you already
locked if the break<br>
happens in the middle of the iteration ?<br>
Note that at skip_recovery: we don't do it. BTW, i see
this issue is already in <br>
the current code.<br>
<br>
Also, maybe now it's better to separate the actual
locking in <br>
amdgpu_device_lock_adev<br>
from the other stuff going on there since I don't
think you would wont to toggle <br>
stuff<br>
like adev->mp1_state back and forth and also the
function name is not <br>
descriptive of<br>
the other stuff going on there anyway.<br>
<br>
Andrey<br>
<br>
<br>
> + }<br>
> + if (get_dev_lock) {<br>
> + if
(!list_is_first(&adev->gmc.xgmi.head,
&hive->device_list))<br>
> +
list_rotate_to_front(&adev->gmc.xgmi.head,
&hive->device_list);<br>
> + device_list_handle =
&hive->device_list;<br>
> + }<br>
> } else {<br>
> -
list_add_tail(&adev->gmc.xgmi.head,
&device_list);<br>
> - device_list_handle =
&device_list;<br>
> + get_dev_lock =
amdgpu_device_lock_adev(adev, hive);<br>
> + tmp_adev = adev;<br>
> + if (get_dev_lock) {<br>
> +
list_add_tail(&adev->gmc.xgmi.head,
&device_list);<br>
> + device_list_handle =
&device_list;<br>
> + }<br>
> + }<br>
> +<br>
> + if (!get_dev_lock) {<br>
> + dev_info(tmp_adev->dev, "Bailing
on TDR for s_job:%llx, as another already in
progress",<br>
> + job ?
job->base.id : -1);<br>
> + r = 0;<br>
> + /* even we skipped this reset,
still need to set the job to guilty */<br>
> + goto skip_recovery;<br>
> }<br>
> <br>
> /* block all schedulers and reset given
job's ring */<br>
> list_for_each_entry(tmp_adev,
device_list_handle, gmc.xgmi.head) {<br>
> - if
(!amdgpu_device_lock_adev(tmp_adev, hive)) {<br>
> - dev_info(tmp_adev->dev,
"Bailing on TDR for s_job:%llx, as another already in
progress",<br>
> - job ?
job->base.id : -1);<br>
> - r = 0;<br>
> - goto skip_recovery;<br>
> - }<br>
> -<br>
> /*<br>
> * Try to put the audio codec into
suspend state<br>
> * before gpu reset started.<br>
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