linux-kernel - Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu

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Message-ID: <alpine.DEB.2.00.1109201102340.8056@router.home>
Date:	Tue, 20 Sep 2011 11:05:15 -0500 (CDT)
From:	Christoph Lameter <cl@...two.org>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andi Kleen <andi@...stfloor.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, Tejun Heo <htejun@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for
 this_cpu_read/write()

On Tue, 20 Sep 2011, Peter Zijlstra wrote:

> On Tue, 2011-09-20 at 10:03 -0500, Christoph Lameter wrote:
> >
> > Well yes the misunderstanding of per cpu operations was one reason why I
> > proposed the discussion on the subject of esoteric kernel synchronization.
> > I do not think that it was accepted.
>
> I don't think anybody here misunderstands it, we're just all very angry
> that its causing so much problems.

What problems? RT does not work with it? The memcg confusion?

> __this_cpu doesn't have preempt debug checks, and there's a lot of
> this_cpu usage that really should have been __this_cpu.

That only works if preemption is disabled when the this_cpu op is being
invoked.


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