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Subject: Re: [PATCH 1/2] jump_labels: Add API to deal with keys embedded in
 structures
To: Peter Zijlstra <peterz@infradead.org>
References: <1474305688-22553-1-git-send-email-marc.zyngier@arm.com>
 <1474305688-22553-2-git-send-email-marc.zyngier@arm.com>
 <20160920094223.GR5012@twins.programming.kicks-ass.net>
Cc: linux-kernel@vger.kernel.org, Jason Baron <jbaron@akamai.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Vladimir Murzin <vladimir.murzin@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>
From: Marc Zyngier <marc.zyngier@arm.com>
Organization: ARM Ltd
Message-ID: <57E1058B.5040800@arm.com>
Date: Tue, 20 Sep 2016 10:46:51 +0100
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On 20/09/16 10:42, Peter Zijlstra wrote:
> On Mon, Sep 19, 2016 at 06:21:27PM +0100, Marc Zyngier wrote:
>> It is desirable to allow static keys to be integrated in structures,
>> as it can lead do slightly more readable code. But the current API
>> only provides DEFINE_STATIC_KEY_TRUE/FALSE, which is not exactly
>> nice and leads to the following idiom:
>>
>> 	static struct {
>> 		int			foo;
>> 		struct static_key_false	key;
>> 	} bar = {
>> 		.key	= STATIC_KEY_FALSE_INIT,
>> 	};
>>
>> 	[...]
>>
>> 	if (static_branch_unlikely(&bar.key))
>> 		foo = -1;
>>
>> which doesn't follow the recommended API, and uses the internals
>> of the static key implementation.
>>
>> This patch introduces DECLARE_STATIC_KEY_TRUE/FALSE, as well as
>> INIT_STATIC_KEY_TRUE/FALSE, which abstract such construct and
>> allow the internals to evolve without having to fix everything else:
>>
>> 	static struct {
>> 		int			 foo;
>> 		DECLARE_STATIC_KEY_FALSE(key);
>> 	} bar = {
>> 		INIT_STATIC_KEY_FALSE(.key),
>> 	};
> 
> Hurm..
> 
> I think I like the first better, it looks more like actual C. Either way
> around you need to now manually match up the type and initializer.

Fair enough, I'll stick to that for the KVM code.

Thanks for the quick feedback.

	M.
-- 
Jazz is not dead. It just smells funny...