linux-kernel - Re: Backport hr-tick fix into .25/.26

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Date:	Tue, 19 Aug 2008 11:22:23 -0700
From:	Greg KH <gregkh@...e.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Justin Madru <jdm64@...ab.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Michal Januszewski <spock@...too.org>,
	Antonino Daplas <adaplas@...il.com>,
	Rafael Wysocki <rjw@...k.pl>,
	Romano Giannetti <romano.giannetti@...il.com>,
	Adrian Bunk <bunk@...nel.org>,
	Jeremy Nickurak <kernel-bugs@...us.rifetech.com>
Subject: Re: Backport hr-tick fix into .25/.26

On Tue, Aug 19, 2008 at 11:33:00AM +0200, Peter Zijlstra wrote:
> On Tue, 2008-08-19 at 11:25 +0200, Ingo Molnar wrote:
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > On Tue, 2008-08-19 at 02:31 +0200, Ingo Molnar wrote:
> > > > * Justin Madru <jdm64@...ab.com> wrote:
> > > > 
> > > > > This commit introduced the bug.
> > > > > commit 8f4d37ec073c17e2d4aa8851df5837d798606d6f
> > > > > sched: high-res preemption tick
> > > > 
> > > > > And this one fixed it
> > > > >
> > > > > commit 31656519e132f6612584815f128c83976a9aaaef
> > > > > sched, x86: clean up hrtick implementation
> > > > 
> > > > hm, the backport of 31656519 is a bit intrusive.
> > > > 
> > > > find below is an (untested!) version of it - i havent even build-tested 
> > > > it. Does it work for you? But this is Greg's call really.
> > > > 
> > > 
> > > It largely depends on all the new IPI stuff that went into 27 as well, 
> > > so I'd be surprised if its easily backportable..
> > 
> > ah, i see. How about a simple patch then that disables hrtick [given 
> > that it's now fixed .27 but the fix is too intrusive to backport]? Would 
> > that be too risky for -stable?
> 
> That's just flipping sched_feat(HRTICK) to 0 by default.

That sounds reasonable, I'll take a patch for that for -stable :)

thanks,

greg k-h
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