linux-kernel - Re: [PATCH] powerpc: warn users of smt-snooze-delay that the API isn't there anymore

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Date:	Wed, 26 Feb 2014 14:45:38 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>,
	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org,
	Wang Dongsheng <dongsheng.wang@...escale.com>,
	linux-kernel@...r.kernel.org,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Paul Mackerras <paulus@...ba.org>,
	Olof Johansson <olof@...om.net>,
	Cody P Schafer <cody@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc: warn users of smt-snooze-delay that the API
 isn't there anymore

On Wed, 2014-02-26 at 09:40 +1100, Benjamin Herrenschmidt wrote:
> On Tue, 2014-02-25 at 13:29 +0530, Deepthi Dharwar wrote:
> > We currently do not use smt-snooze-delay in the kernel.
> > The sysfs entries needs to  be retained until we do a clean up
> > ppc64_cpu
> > util that uses these entries to determine SMT,
> > clean up patch for this has already been posted out by Prerna.
> > Once, we have the ppc64_cpu changes in, we can look to clean up these
> > parts from the kernel.
> 
> We generally shouldn't change user visible interfaces.
> 
> People still have old versions of ppc64_cpu, we must not break them

Yeah we can't remove the file entirely, at least for a few more years.

ppc64_cpu should never have used that file to determine if a cpu existed, but
it did, so we're stuck with it.

What we can do is remove the unused percpu, and just leave the file in sysfs,
and have it print a warning when anyone touches it.

cheers


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