Re: [PATCH] drm/amdgpu: Fix regression in adjusting power table/profile

[Matt Coffin <mcoffin13@gmail.com>]

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I actually *just* finished my bisect, and arrived at the same
conclusion. The hang appears to be introduced in
edad8312cbbf9a33c86873fc4093664f150dd5c1.

There are some conflicts with an automatic `git revert`, so I'm picking
through the changes now to fully understand what happened and come up
with a fix.

Thanks again for the help,
Matt

On 7/31/20 2:20 PM, Paweł Gronowski wrote:
> Hello again,
> 
> I just finished a bisect of amd-staging-drm-next and it looks like
> the hang is first introduced in edad8312cbbf9a33c86873fc4093664f150dd5c1
> ("drm/amdgpu: fix system hang issue during GPU reset").
> 
> It is a bit tricky, because it is commited on top of my first faulty patch
> 7173949df45482 ("drm/amdgpu: Fix NULL dereference in dpm sysfs handlers") so
> it needs to be reverted fix the premature -INVAL.
> 
> Test case:
>   sudo sh -c 'echo "s 0 305 750" > /sys/class/drm/card0/device/pp_od_clk_voltage'
> Results:
>   edad8312cbbf9a3 + revert 7173949df45482 = hang
>   edad8312cbbf9a3~1 + revert 7173949df45482 = no hang
> 
> Could you confirm that you get the same results?
> 
> Thanks,
> Paweł Gronowski
> 
> 
> On Fri, Jul 31, 2020 at 03:34:40PM +0200, Paweł Gronowski wrote:
>> Hey Matt,
>>
>> I have just tested the amd-staging-drm-next branch 
>> (dd654c76d6e854afad716ded899e4404734aaa10) with my patches reverted
>> and I can reproduce your issue with:
>>
>>   sudo sh -c 'echo "s 0 305 750" > /sys/class/drm/card0/device/pp_od_clk_voltage'
>>
>> Which makes the sh hang with 100% usage.
>>
>> The issue does not happen on the mainline (d8b9faec54ae4bc2fff68bcd0befa93ace8256ce)
>> both without and with my patches reapplied.
>> So the problem must be related to some commit that is present in the
>> amd-staging-drm-next but not in the mainline.
>>
>>
>> Paweł Gronowski
>>
>> On Thu, Jul 30, 2020 at 06:34:14PM -0600, Matt Coffin wrote:
>>> Hey Pawel,
>>>
>>> I did confirm that this patch *introduced* the issue both with the
>>> bisect, and by testing reverting it.
>>>
>>> Now, there's a lot of fragile pieces in the dpm handling, so it could be
>>> this patch's interaction with something else that's causing it and it
>>> may well not be the fault of this code, but this is the patch that
>>> introduced the issue.
>>>
>>> I'll have some more time tomorrow to try to get down to root cause here,
>>> so maybe I'll have more to offer then.
>>>
>>> Thanks for taking a look,
>>> Matt
>>>
>>> On 7/30/20 6:31 PM, Paweł Gronowski wrote:
>>>> Hello Matt,
>>>>
>>>> Thank you for your testing. It seems that my gpu (RX 570) does not support the
>>>> vc setting so I can not exactly reproduce the issue. However I did trace the
>>>> code path the test case takes and it seems to correctly pass through the while
>>>> loop that parses the input and fails only in amdgpu_dpm_odn_edit_dpm_table.
>>>> The 'parameter' array is populated the same way as the original code did. Since
>>>> the amdgpu_dpm_odn_edit_dpm_table is reached, I think that your problem is
>>>> unfortunately caused by something else.
>>>>
>>>>
>>>> Paweł Gronowski
>>>>
>>>> On Thu, Jul 30, 2020 at 08:49:41AM -0600, Matt Coffin wrote:
>>>>> Hello all, I just did some testing with this applied, and while it no
>>>>> longer returns -EINVAL, running `sudo sh -c 'echo "vc 2 2150 1195" >
>>>>> /sys/class/drm/card1/device/pp_od_clk_voltage'` results in `sh` spiking
>>>>> to, and staying at 100% CPU usage, with no indicating information in
>>>>> `dmesg` from the kernel.
>>>>>
>>>>> It appeared to work at least ONCE, but potentially not after.
>>>>>
>>>>> This is not unique to Navi, and caused the problem on a POLARIS10 card
>>>>> as well.
>>>>>
>>>>> Sorry for the bad news, and thanks for any insight you may have,
>>>>> Matt Coffin
>>>>>
>>>>> On 7/29/20 8:53 PM, Alex Deucher wrote:
>>>>>> On Wed, Jul 29, 2020 at 10:20 PM Paweł Gronowski <me@woland.xyz> wrote:
>>>>>>>
>>>>>>> Regression was introduced in commit 38e0c89a19fd
>>>>>>> ("drm/amdgpu: Fix NULL dereference in dpm sysfs handlers") which
>>>>>>> made the set_pp_od_clk_voltage and set_pp_power_profile_mode return
>>>>>>> -EINVAL for previously valid input. This was caused by an empty
>>>>>>> string (starting at the \0 character) being passed to the kstrtol.
>>>>>>>
>>>>>>> Signed-off-by: Paweł Gronowski <me@woland.xyz>
>>>>>>
>>>>>> Applied.  Thanks!
>>>>>>
>>>>>> Alex
>>>>>>
>>>>>>> ---
>>>>>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c | 9 +++++++--
>>>>>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>>>>> index ebb8a28ff002..cbf623ff03bd 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_pm.c
>>>>>>> @@ -778,12 +778,14 @@ static ssize_t amdgpu_set_pp_od_clk_voltage(struct device *dev,
>>>>>>>                 tmp_str++;
>>>>>>>         while (isspace(*++tmp_str));
>>>>>>>
>>>>>>> -       while ((sub_str = strsep(&tmp_str, delimiter)) != NULL) {
>>>>>>> +       while ((sub_str = strsep(&tmp_str, delimiter)) && *sub_str) {
>>>>>>>                 ret = kstrtol(sub_str, 0, &parameter[parameter_size]);
>>>>>>>                 if (ret)
>>>>>>>                         return -EINVAL;
>>>>>>>                 parameter_size++;
>>>>>>>
>>>>>>> +               if (!tmp_str)
>>>>>>> +                       break;
>>>>>>>                 while (isspace(*tmp_str))
>>>>>>>                         tmp_str++;
>>>>>>>         }
>>>>>>> @@ -1635,11 +1637,14 @@ static ssize_t amdgpu_set_pp_power_profile_mode(struct device *dev,
>>>>>>>                         i++;
>>>>>>>                 memcpy(buf_cpy, buf, count-i);
>>>>>>>                 tmp_str = buf_cpy;
>>>>>>> -               while ((sub_str = strsep(&tmp_str, delimiter)) != NULL) {
>>>>>>> +               while ((sub_str = strsep(&tmp_str, delimiter)) && *sub_str) {
>>>>>>>                         ret = kstrtol(sub_str, 0, &parameter[parameter_size]);
>>>>>>>                         if (ret)
>>>>>>>                                 return -EINVAL;
>>>>>>>                         parameter_size++;
>>>>>>> +
>>>>>>> +                       if (!tmp_str)
>>>>>>> +                               break;
>>>>>>>                         while (isspace(*tmp_str))
>>>>>>>                                 tmp_str++;
>>>>>>>                 }
>>>>>>> --
>>>>>>> 2.25.1
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>> amd-gfx@lists.freedesktop.org
>>>>>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>>>>>> _______________________________________________
>>>>>> amd-gfx mailing list
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>>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>>


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