[Intel-gfx] [PATCH] drm/i915: Don't pin LRC in GGTT when dumping in debugfs

[Chris Wilson]

On Thu, Nov 20, 2014 at 11:25:57AM +0000, Daniel, Thomas wrote:
> > -----Original Message-----
> > From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> > Sent: Thursday, November 20, 2014 11:16 AM
> > To: Daniel, Thomas
> > Cc: intel-gfx at lists.freedesktop.org; akash-goels at gmail.com
> > Subject: Re: [Intel-gfx] [PATCH] drm/i915: Don't pin LRC in GGTT when
> > dumping in debugfs
> > 
> > On Thu, Nov 20, 2014 at 11:12:05AM +0000, Thomas Daniel wrote:
> > > LRC object does not need to be mapped into the GGTT when dumping. Just
> > > use pin_pages. A side-effect of this patch is that a compiler warning
> > > goes away (not checking return value of i915_gem_obj_ggtt_pin).
> > 
> > Please explain why you need to pin the pages.
> I suppose I don't as this is protected by the struct mutex and unpin is called before returning.

The question is: do we need protection against kmalloc and a potential
call into the shrinker who may steal the pages from underneath us. Here,
we only do a seq_printf() under the lock after get_pages() and that uses
a preallocated buffer.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre