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

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Message-ID: <m2ehzcdkf2.fsf@firstfloor.org>
Date:	Mon, 19 Sep 2011 19:20:17 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [RFC][PATCH 0/5] Introduce checks for preemptable code for this_cpu_read/write()

Steven Rostedt <rostedt@...dmis.org> writes:

> I just found out that the this_cpu_*() functions do not perform the
> test to see if the usage is in atomic or not. Thus, the blind
> conversion of the per_cpu(*, smp_processor_id()) and the get_cpu_var()
> code to this_cpu_*() introduce the regression to detect the hard
> to find case where a per cpu variable is used in preempt code that
> migrates and causes bugs.


Didn't preempt-rt recently get changed to not migrate in kernel-preempt
regions. How about just fixing the normal preemption to not do this
either.

Then all these complications wouldn't be necessary and a whole lot 
of code related to this could be removed too, and you would still
have less bugs.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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