linux-kernel - Re: 3.5.x boot hang after conflicting fb hw usage <driver> vs VESA VGA

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Date:	Sun, 19 Aug 2012 22:13:09 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Dave Airlie <airlied@...il.com>
CC:	"Justin M. Forbes" <jforbes@...hat.com>,
	linux-kernel@...r.kernel.org, kernel-team@...oraproject.org,
	dri-devel@...ts.freedesktop.org
Subject: Re: 3.5.x boot hang after conflicting fb hw usage <driver> vs VESA
 VGA - removing generic driver

On 08/17/12 15:55, Dave Airlie wrote:

> On Sat, Aug 18, 2012 at 8:54 AM, Dave Airlie <airlied@...il.com> wrote:
>> On Sat, Aug 18, 2012 at 8:28 AM, Randy Dunlap <rdunlap@...otime.net> wrote:
>>> On 08/17/2012 03:25 PM, Justin M. Forbes wrote:
>>>
>>>> for <driver>, we have verified cases on inteldrmfb, radeondrmfb, and
>>>> cirrusdrmfb.
>>>>
>>>> This is the last message displayed before the system hangs.  This seems
>>>> to be hitting a large number of users in Fedora, though certainly not
>>>> everyone.  This started happening with the 3.5 updates, and is still an
>>>> issue.  It appears to be a race condition, because various things have
>>>> allowed boot to continue for some users, though there is no clear work
>>>> around. Has anyone else run across this?  Any ideas.  For more
>>>> background we have the following bugs:
>>>>
>>>> inteldrmfb:
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=843826
>>>>
>>>> radeondrmfb:
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=845745
>>>>
>>>> cirrusdrmfb <kvm>:
>>>> https://bugzilla.redhat.com/show_bug.cgi?id=843860
>>>>
>>>> It should be noted that the conflicting fb hw usage message is not new,
>>>> it has been around for a while, but this is the last message seen before
>>>> the hang.
>>>
>>>
>>> Hi,  (adding dri-devel mailing list)
>>>
>>>
>>> I started seeing this problem on 3.5-rc6.
>>>
>>> AFAICT, the system is not actually hung, it's just that no output
>>> is showing up on the real (physical) output device (display) -- it's
>>> going somewhere else (or to the bit bucket).
>>>
>>
>> Can we bisect this at all?

I guess I'll have to try again.  My first attempt did not
prove anything, I think because the conflict does not happen
100% of the time (i.e., it feels like a timing problem).

>> I worry the intel one will bisect to where we moved the conflict
>> resolution earlier, but I'd like to see if applying that patch earlier
>> causes the issue, since radeon has it.

Do you know of a specific commit that I could revert and test?

>> I haven't reproduced this on any hw I own, I also can't get it under qemu.
> 
> I'm also wondering whether this grub2 related in some way, grub2 is
> starting to mess with the graphics adapter pointlessly.
> 
> Dave.



-- 
~Randy
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