linux-kernel - Re: [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads trainwreck

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Message-ID: <20110720193925.GB7910@elte.hu>
Date:	Wed, 20 Jul 2011 21:39:25 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ben Greear <greearb@...delatech.com>,
	Ed Tomlinson <edt@....ca>, linux-kernel@...r.kernel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	eric.dumazet@...il.com, darren@...art.com, patches@...aro.org,
	edward.tomlinson@...o.bombardier.com
Subject: Re: [PATCH rcu/urgent 0/6] Fixes for RCU/scheduler/irq-threads
 trainwreck


* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:

> If my guess is correct, then the minimal non-RCU_BOOST fix is #4 
> (which drags along #3) and #6.  Which are not one-liners, but 
> somewhat smaller:
> 
>  b/kernel/rcutree_plugin.h |   12 ++++++------
>  b/kernel/softirq.c        |   12 ++++++++++--
>  kernel/rcutree_plugin.h   |   31 +++++++++++++++++++++++++------
>  3 files changed, 41 insertions(+), 14 deletions(-)

That's half the patch size and half the patch count.

PeterZ's question is relevant: since we apparently had similar bugs 
in v2.6.39 as well, what changed in v3.0 that makes them so urgent
to fix?

If it's just better instrumentation that proves them better then i'd 
suggest fixing this in v3.1 and not risking v3.0 with an unintended 
side effect.

Thanks,

	Ingo
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