Re: [PATCH 5/5] drm/i915: Fix error capture on BYT/BDW

[Ben Widawsky <ben@bwidawsk.net>]

On Sun, Jan 26, 2014 at 07:55:59PM +0000, Chris Wilson wrote:
> On Sun, Jan 26, 2014 at 11:05:40AM -0800, Ben Widawsky wrote:
> > On Sun, Jan 26, 2014 at 11:47:40AM +0000, Chris Wilson wrote:
> > > On Fri, Jan 24, 2014 at 06:17:45PM -0800, Ben Widawsky wrote:
> > > > The previous check during error capture of whether or not the current VM
> > > > should be scanned used, gen < 7. That was more or less trying to
> > > > determine if there was a full PPGTT. At the time, this was sort of what
> > > > I meant to do because I was more interested in working backwards from
> > > > hardware state. However, this is incorrect because it will not include
> > > > platforms that are greater than gen7, and not having PPGTT.  Example
> > > > would be BYT which is gen7 but doesn't have PPGTT, BDW, or any platform
> > > > greater than gen7 with the PPGTT module parameter invoked.
> > > > 
> > > > I am /assuming/ BYT was broken, I have not actually checked.
> > > > 
> > > > While here, clean up the file a bit to avoid duplicate reads (now that
> > > > the PPGTT info is in the error state).
> > > > 
> > > > I think Mika/Chris may have been looking at this too.
> > > 
> > > Sure, we are looking (for identifying the guilty request/batch) by using
> > > the older, simpler mechanism of finding the first incomplete request. I
> > > think that search is now definite since we preallocate the request and no
> > > longer do request collascing if ENOMEM (i.e. there is a 1:1 relationship
> > > between seqno/batch/request).
> > > 
> > > That should also apply here and be much simpler.
> > 
> > How does that solve hangs which aren't caused by requests?
> 
> Was that an intentional rhetorical question?
> 
> The code you touch here only deals with requests - finding the current
> batchbuffer if any.
> -Chris
> 

It wasn't rhetorical. I temporarily ignored that all batches are tied to
a request.

So what's the plan now? Just looking at the callers, we seem to have a
couple of callers that can't easily identify the bad request.

-- 
Ben Widawsky, Intel Open Source Technology Center