Re: Kernel Oops on 3.14.66

[Dave Gordon <david.s.gordon@intel.com>]

> 2016-04-27 12:03 GMT+02:00 Dave Gordon <david.s.gordon@intel.com>:
>
>> On 27/04/16 10:19, Andreas Lampersperger wrote:
>>
>>> Hello,
>>>
>>> has anyone here a hint for me, what can cause this error.
>>> The error occures highly sporadic on different machines with intel hd
>>> graphics (ivb_gt1).
>>> I did also some kernel coredumps and found out, that the failed
>>> paging request came from drm_i915_gem_request->list.prev or ->list.next.
>>>
>>> Thank you
>>> Andreas
>>
>> Try this patch.
>>
>> .Dave.
>
On 27/04/16 13:20, Andreas Lampersperger wrote:
> Hi Dave,
>
> thank you for the patch, but I'm using longtime kernel 3.14.66 and so the
> patch does not fit.
> Do you have any suggestions for that kernel?
>
> Andreas

I have no idea what the code would look like in that version; do you 
have any way to get the git commit hash or tag of the i915 driver?

But essentially, if you have the kernel sources for that version, you 
could look for a line that allocates a "struct drm_i915_gem_request". It 
might be

     req = kmem_cache_zalloc(dev_priv->requests, GFP_KERNEL);

or in older versions it might be

     request = kzalloc(sizeof(*request), GFP_KERNEL);

or some other variation. It should of course be followed by a test for 
successful allocation, e.g.

     if (request == NULL)
         return -ENOMEM;

If you can find that line (or lines, at one time there were TWO such 
places), then you just have to add

     INIT_LIST_HEAD(&request->list);

after the test-for-NULL, or anywhere inline thereafter. For example:

     request = kzalloc(sizeof(*request), GFP_KERNEL);
     if (request == NULL)
         return -ENOMEM;

     ret = i915_gem_get_seqno(ring->dev, &request->seqno);
     if (ret) {
         kfree(request);
         return ret;
     }

+   INIT_LIST_HEAD(&request->list);
     kref_init(&request->ref);
     request->ring = ring;
     request->uniq = dev_private->request_uniq++;

HTH,
.Dave.
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