VT_WAITACTIVE (was: Re: ffreep support on Geode LX (XO-1))

[Sascha Silbe]

On Thu, May 07, 2009 at 04:21:35PM -0400, Daniel Drake wrote:

>> i think you're exactly right -- the fact that ul-warning completes
>> when you manually switch screens is pretty convincing.  i'm
>> amazed the vt system has never grown a new api of some sort to
>> fix this problem.  because powerd puts up an additional shutdown
>> splash screen prior to the ul-warning screen, the sequencing is
>> perturbed, and i see it (the race) more often.
>>
>> i think we should apply the bandaid of a retry to the chvt code --
>> i.e., add a timeout to the wait, and retry (or, at the very
>> least, exit) if it expires.  i actually went in to make the code
>> changes the other day, but i backed off when i realized the
>> source was in pyrex, not C.  i realized i wasn't sure i'd be able
>> to do the signal handling successfully (in the time i'd allotted
>> myself, at any rate).
> I encountered this bug while working on another product, and came up
> with a solution that isn't quite so complex.  It involves not using
> VT_WAITACTIVE and instead just polling the v_active member of the
> VT_GETSTATE result in a loop, retrying the VT_ACTIVATE until happy.
>
> Site seems down at the moment but here it is from google's cache:
> http://74.125.47.132/search?q=cache:dmF2nkv9GL0J:www.brontes3d.com/opensource/dist/v1.2/overlay/sys-apps/kbd/files/kbd-1.12-chvt-userwait.patch+chvt+userwait&cd=1&hl=en&ct=clnk&gl=py&client=firefox-a
>
> AFAIK the patch was never accepted upstream (due to it being very
> inactive or dead) but I definitely submitted it.
>
> This is something that we could perhaps roll into bobby's work on
> bootanim/ul-warning, assuming it is affected in the first place...
[Fullquote to refresh everyones memory because it's a rather old mail 
I'm replying to]

There's been some work in 2.6.32 on some shiny new interface that is 
supposed not to have the VT_WAITACTIVE bugs: [1]
Maybe ul-warning can switch to that once the olpc tree has been rebased 
on top of 2.6.32... (or maybe not; haven't taken any look at it)


[1] 
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=8b92e87d39bfd046e7581e1fe0f40eac40f88608

CU Sascha

-- 
http://sascha.silbe.org/
http://www.infra-silbe.de/
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