linux-kernel - Re: [PATCH 3/8] jump_label: introduce DEFINE_STATIC_KEY_{TRUE,FALSE}

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Message-ID: <20150821032334.GB12451@pek-khao-d1.corp.ad.wrs.com>
Date:	Fri, 21 Aug 2015 11:23:34 +0800
From:	Kevin Hao <haokexin@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Michael Ellerman <mpe@...erman.id.au>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 3/8] jump_label: introduce
 DEFINE_STATIC_KEY_{TRUE,FALSE}_ARRAY macros

On Thu, Aug 20, 2015 at 08:31:58PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 20, 2015 at 08:14:31PM +0800, Kevin Hao wrote:
> > These are used to define a static_key_{true,false} array.
> 
> Yes but why...
> 
> there might have been some clue in the patches you didn't send me, but
> since you didn't send them, I'm left wondering.

Sorry for the confusion. In order to use jump label for the
{cpu,mmu}_has_feature() functions on powerpc, we need to declare an array of
32 or 64 static_key_true (one static_key_true for each cpu or mmu feature).
The following are the two patches which depends on this patch.
  https://lkml.org/lkml/2015/8/20/355
  https://lkml.org/lkml/2015/8/20/356

So far only DEFINE_STATIC_KEY_TRUE_ARRAY macro is used, but I think it may seem
canonical to define the macros for both true or false keys at the same time.

Thanks,
Kevin

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