lkml.org 
[lkml]   [2012]   [Mar]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: inode->i_wb_list corruption.
Date
<#part sign=pgpmime>
On Mon, 12 Mar 2012 19:26:30 -0400, Dave Jones <davej@redhat.com> wrote:

> Thinking about how the GTT could contain stale pointers, I came up with this scenario:
>
> Before we begin the thaw, the initramfs sets up a framebuffer.
> This causes the GTT to be setup.

Yes. The frame buffer is allocated as regular kernel pages, of course.

> - Thaw begins, hardware state still points to the GTT setup by the modesetting code.
> At this point, any graphics operations are going to cause writes through
> those translations. Bad news if we just wrote a bunch of thawed data
> there.

The question is what data could still be pending there; we're running
just fbcon at that point, which uses only write-through
access. Presumably, any fbdev writes will have been long-since finished
once we start the new kernel.

> - Thaw begins, and data is written over the GTT setup by the initramfs, but
> the hardware registers still points at it, until thaw is complete, when we
> reprogram the GTT registers to their pre-hibernate values.

I'm not sure how the new kernel could manage to do any writes through
this though -- it shouldn't touch the frame buffer until it has thawed
the video driver, right?

> If we could somehow set modeset=0 automatically if we detect a hibernate
> partition it would probably 'solve' it, but I suspect the real answer
> would be to do GTT teardown before we do a thaw.

We've got a ton of memory available in the 'stolen' area which the BIOS
used as a frame buffer; we should be able to switch to that before the
switch, if we decide that this is necessary.

--
keith.packard@intel.com


\
 
 \ /
  Last update: 2012-03-13 01:09    [W:0.059 / U:0.184 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site