linux-kernel - Re: [git pull] scheduler fixes

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Message-ID: <20071204164124.447a5c36@mandriva.com.br>
Date:	Tue, 4 Dec 2007 16:41:24 -0200
From:	"Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>
To:	Greg KH <greg@...ah.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	herton@...driva.com.br, dvgevers@...all.nl
Subject: Re: [git pull] scheduler fixes

Em Tue, 4 Dec 2007 10:28:51 -0800
Greg KH <greg@...ah.com> escreveu:

| On Tue, Dec 04, 2007 at 05:18:27PM +0100, Ingo Molnar wrote:
| > 
| > * Ingo Molnar <mingo@...e.hu> wrote:
| > 
| > > The problem is on SMP: if sched_rr_get_interval() gets a task from an 
| > > otherwise idle runqueue, then rq->load.weight is 0. Normally 
| > > sched_slice() is only used on a busy runqueue. So the correct fixup 
| > > site is not in sched_slice() but in sys_sched_rr_get_interval() - i'm 
| > > working on the right fix, i hope to be able to send a pull request in 
| > > a few minutes.
| > 
| > the problem is on UP too - if there are no SCHED_OTHER tasks. I've 
| > tested the fix and it solves the problem for various combinations of 
| > crash.c. I've updated sched.git, please pull it from:
| > 
| >    git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched.git
| > 
| > It has another commit besides this fix. Thanks,
| 
| Can you make up something that I can apply for 2.6.23-stable?  or is
| this not an issue on that tree?

 FWIW I couldn't reproduce the problem with 2.6.23.9. sched_slice()
is quite different on that kernel and _maybe_ it won't never divide
by zero.

 My original report on vendor-sec was wrong. I've said that 2.6.23.9
had the same bug but turns out the kernel I tested had the Ingo's
CFS backport patch applied. I didn't know that, I thought it was a
vanilla kernel.

 Btw, I think it's important to release a new CFS backport patch
because maybe some distro is using it (Mandriva stable kernel is
using the CFS backport patch, but we didn't update to latest
version yet).

-- 
Luiz Fernando N. Capitulino
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