Reworking of GPU reset logic

Jerome Glisse j.glisse at
Wed Apr 25 07:26:12 PDT 2012

On Wed, Apr 25, 2012 at 9:46 AM, Alex Deucher <alexdeucher at> wrote:
> 2012/4/25 Dave Airlie <airlied at>:
>> 2012/4/25 Christian König <deathsimple at>:
>>> On 21.04.2012 16:14, Jerome Glisse wrote:
>>>> 2012/4/21 Christian König<deathsimple at>:
>>>>> On 20.04.2012 01:47, Jerome Glisse wrote:
>>>>>> 2012/4/19 Christian König<deathsimple at>:
>>>>>>> This includes mostly fixes for multi ring lockups and GPU resets, but
>>>>>>> it
>>>>>>> should general improve the behavior of the kernel mode driver in case
>>>>>>> something goes badly wrong.
>>>>>>> On the other hand it completely rewrites the IB pool and semaphore
>>>>>>> handling, so I think there are still a couple of problems in it.
>>>>>>> The first four patches were already send to the list, but the current
>>>>>>> set
>>>>>>> depends on them so I resend them again.
>>>>>>> Cheers,
>>>>>>> Christian.
>>>>>> I did a quick review, it looks mostly good, but as it's sensitive code
>>>>>> i would like to spend sometime on
>>>>>> it. Probably next week. Note that i had some work on this area too, i
>>>>>> mostly want to drop all the debugfs
>>>>>> related to this and add some new more usefull (basicly something that
>>>>>> allow you to read all the data
>>>>>> needed to replay a locking up ib). I also was looking into Dave reset
>>>>>> thread and your solution of moving
>>>>>> reset in ioctl return path sounds good too but i need to convince my
>>>>>> self that it encompass all possible
>>>>>> case.
>>>>>> Cheers,
>>>>>> Jerome
>>>>> After sleeping a night over it I already reworked the patch for improving
>>>>> the SA performance, so please wait at least for v2 before taking a look
>>>>> at
>>>>> it :)
>>>>> Regarding the debugging of lockups I had the following on my "in mind
>>>>> todo"
>>>>> list:
>>>>> 1. Rework the chip specific lockup detection code a bit more and probably
>>>>> clean it up a bit.
>>>>> 2. Make the timeout a module parameter, cause compute task sometimes
>>>>> block a
>>>>> ring for more than 10 seconds.
>>>>> 3. Keep track of the actually RPTR offset a fence is emitted to
>>>>> 3. Keep track of all the BOs a IB is touching.
>>>>> 4. Now if a lockup happens start with the last successfully signaled
>>>>> fence
>>>>> and dump the ring content after that RPTR offset till the first not
>>>>> signaled
>>>>> fence.
>>>>> 5. Then if this fence references to an IB dump it's content and the BOs
>>>>> it
>>>>> is touching.
>>>>> 6. Dump everything on the ring after that fence until you reach the RPTR
>>>>> of
>>>>> the next fence or the WPTR of the ring.
>>>>> 7. If there is a next fence repeat the whole thing at number 5.
>>>>> If I'm not completely wrong that should give you practically every
>>>>> information available, and we probably should put that behind another
>>>>> module
>>>>> option, cause we are going to spam syslog pretty much here. Feel free to
>>>>> add/modify the ideas on this list.
>>>>> Christian.
>>>> What i have is similar, i am assuming only ib trigger lockup, before each
>>>> ib
>>>> emit to scratch reg ib offset in sa and ib size. For each ib keep bo list.
>>>> On
>>>> lockup allocate big memory to copy the whole ib and all the bo referenced
>>>> by the ib (i am using my bof format as i already have userspace tools).
>>>> Remove all the debugfs file. Just add a new one that gave you the first
>>>> faulty
>>>> ib. On read of this file kernel free the memory. Kernel should also free
>>>> the
>>>> memory after a while or better would be to enable the lockup copy only if
>>>> some kernel radeon option is enabled.
>>> Just resent my current patchset to the mailing list, it's not as complete as
>>> your solution, but seems to be a step into the right direction. So please
>>> take a look at them.
>>> Being able to generate something like a "GPU crash dump" on lockup sounds
>>> like something very valuable to me, but I'm not sure if debugfs files are
>>> the right direction to go. Maybe something more like a module parameter
>>> containing a directory, and if set we dump all informations (including bo
>>> content) available in binary form (instead of the current human readable
>>> form of the debugfs files).
>> Do what intel driver does, create a versioned binary debugfs file with
>> all the error state in it for a lockup,
>> store only one of these at a time, run a userspace tool to dump it out
>> into something you can
>> upload or just cat the file and upload it.
>> You don't want the kernel writing to dirs on disk under any circumstances
> We have an internal binary format for dumping command streams and
> associated buffers, we should probably use that so that we can better
> take advantage of existing internal tools.
> Alex

I really would like to drop all the debugfs file related to ib/ring with this
patchset. Note that i also have a binary format to replay command stream
the blob format. It has all the information needed to replay on the
open driver and tools are their (my joujou repo on fdo).


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