linux-kernel - Re: [RFC/RFT PATCH] sched: automated per tty task groups

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Date:	Thu, 21 Oct 2010 12:22:15 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
Cc:	Mike Galbraith <efault@....de>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC/RFT PATCH] sched: automated per tty task groups

* Markus Trippelsdorf (markus@...ppelsdorf.de) wrote:
> On Thu, Oct 21, 2010 at 10:52:45AM +0200, Mike Galbraith wrote:
> > On Thu, 2010-10-21 at 10:48 +0200, Markus Trippelsdorf wrote:
> > > On Thu, Oct 21, 2010 at 10:11:55AM +0200, Mike Galbraith wrote:
> > > > On Wed, 2010-10-20 at 04:56 +0200, Ingo Molnar wrote:
> > > > 
> > > > > Mind doing more of the tty->desktop renames/generalizations as Linus suggested, and 
> > > > > resend the patch?
> > > > 
> > > > Here she comes.  Better/Worse?
> > > > 
> > > > Changes:
> > > > - tty->autogroup.
> > > > - only autogroup fair class tasks.
> > > > - removed dainbramaged sleeper vruntime twiddling.
> > > > - removed paranoid locking.
> > > > - removed noop detatch code.
> > > > 
> > > > > I'd also suggest to move it out of EXPERIMENTAL - we dont really do that for core 
> > > > > kernel features as most distros enable CONFIG_EXPERIMENTAL so it's a rather 
> > > > > meaningless distinction. Since the feature is default-n, people will get the old 
> > > > > scheduler by default but can also choose this desktop-centric scheduling mode.
> > > > > 
> > > > > I'd even argue to make it default-y, because this patch clearly cures a form of 
> > > > > kbuild cancer.
> > > > 
> > > > You top dogs can make the default call.. it it's accepted that is ;-)
> > > > 
> > > > Marcus:  care to try the below?  Works fine for me (but so did first
> > > > cut).  It depends on the attached patch, and applied to virgin shiny new
> > > > 2.6.36.
> > > 
> > > Works fine interactively, but I still get the same kernel BUG on reboot
> > > time as before. Would a photo of the trace help you?
> > 
> > Odd.  Yeah, please send me the photo and your .config.
> 
> OK here you go. Both are attached.

In the backtrace, the scheduler is called from:

do_group_exit()
  __dequeue_signal()
    do_exit()

given that task_group() is called from many spots in the scheduler, I wonder if
some checks making sure that tg != NULL in task_group() would be appropriate ?
Also checking that p->signal is non-NULL in autogroup_attach_tty() might help.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
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