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

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Message-ID: <5032BDF5.1060800@xenotime.net>
Date:	Mon, 20 Aug 2012 15:45:09 -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 08/19/2012 10:22 PM, Dave Airlie wrote:

> On Mon, Aug 20, 2012 at 3:13 PM, Randy Dunlap <rdunlap@...otime.net> wrote:
>> 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?
> 
> 9f846a16d213523fbe6daea17e20df6b8ac5a1e5
> 
> might work, but it just changes the timing mostly.
> 
> also testing 3.4 with that on top would be good.


That commit doesn't apply cleanly to 3.4, but reverting
it on 3.5-rc6 (where I first saw the problem) allows me to boot
3.5-rc6 multiple times without a problem.

Maybe Justin can get more stable testing done also..

thanks,
-- 
~Randy
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