linux-kernel - Re: How do I increment a per-CPU variable without warning?

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Message-ID: <alpine.DEB.2.10.1404161008390.9945@gentwo.org>
Date:	Wed, 16 Apr 2014 10:12:16 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Dave Jones <davej@...hat.com>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, tj@...nel.org, grygorii.strashko@...com
Subject: Re: How do I increment a per-CPU variable without warning?

On Wed, 16 Apr 2014, Peter Zijlstra wrote:

> You really want to disable preemption around there. The proper old way
> would've been get_cpu_var()/put_cpu_var().

get_cpu_var and put_cpu_var is still the correct way of doing things if
you need to access multiple per cpu variables.

The problem that I want to solve is the varied use of
__get_cpu_var for address calculations, per cpu variable assignment,
structure copying and per cpu variable access. The this_cpu ops can avoid
address calculations using segment prefixes. Plus the changes clarify what
is actuallly going on.

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