linux-kernel - Re: Old -rt patches

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Message-ID: <46B832D0.5030803@free.fr>
Date:	Tue, 07 Aug 2007 10:52:32 +0200
From:	John Sigler <linux.kernel@...e.fr>
To:	paulmck@...ux.vnet.ibm.com
CC:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...e.hu, tglx@...utronix.de
Subject: Re: Old -rt patches

Paul E. McKenney wrote:

> John Sigler wrote:
> 
>> I wrote a Linux app where I need high-resolution timers. I went all the 
>> way and installed the -rt patch, which includes the -hrt patches, as far 
>> as I understand.
>>
>> Since I could not afford to change kernels with every new release, I 
>> decided to track the 2.6.20 branch (arbitrarily).
>>
>> At this point I'm using 2.6.20.7-rt8 (-rt8 was the last patch to the 
>> 2.6.20 branch). (I see 2.6.20 is already up to .15)
>>
>> I see a lot of patches going into the -rt patch, but development moved 
>> on to 2.6.21, then 2.6.22, and now 2.6.23, following mainline.
>>
>> I'm not a kernel hacker, so I don't claim to understand the patches, but 
>> the comments sound like a few bugs are fixed here and there. I can't 
>> tell whether these bugs also exist in previous kernels or only appeared 
>> in newer kernels. Even if I knew, I probably wouldn't have the expertise 
>> to back-port the patch.
>>
>> I'm seeing weird behavior in my app, when it has been running 2-4 days. 
>> The timers start to act out, and all hell breaks loose. Basically, I 
>> have no idea what's going on...
>>
>> My question is: is it possible that there is a bug in 2.6.20-rt8 that 
>> has been fixed in subsequent -rt patches (there's a 2.6.21.6-rt21 and a 
>> 2.6.22.1-rt9)? In other words, if I give 2.6.21.6-rt8 or 2.6.22.1-rt9 a 
>> spin, is it possible that my weird behavior disappears?
>>
>> I'm not saying that it's impossible for the bug to be in my app, but the 
>> app is small enough that I'm fairly confident there's no problem there.
> 
> Would you be willing to post your app so people could try to reproduce
> your bug?

Hello Paul,

I cannot provide the app "as is" (I fear the paranoid PHB would 
spontaneously combust). If time permits, I will try to make a small 
testcase to exhibit the problem.

Regards.
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