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Date: Mon, 27 Jul 2015 11:07:37 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: linux-kernel@vger.kernel.org, mingo@kernel.org
Cc: jasonbaron0@gmail.com, bp@alien8.de, luto@amacapital.net,
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Subject: Re: [RFC][PATCH 5/7] jump_label: Rework update logic
Message-ID: <20150727090737.GO19282@twins.programming.kicks-ass.net>
References: <20150724175209.814173117@infradead.org>
 <20150724175823.013936034@infradead.org>
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On Fri, Jul 24, 2015 at 07:52:14PM +0200, Peter Zijlstra wrote:
> @@ -330,8 +318,7 @@ static int jump_label_add_module(struct
>  		jlm->next = key->next;
>  		key->next = jlm;
>  
> -		if (jump_label_type(key) == JUMP_LABEL_JMP)
> -			__jump_label_update(key, iter, iter_stop, JUMP_LABEL_JMP);
> +		__jump_label_update(key, iter, iter_stop);
>  	}
>  
>  	return 0;

That is the fail; the arch_jump_label_transform() function (at least on
x86) double checks that we're changing the branch, so we cannot
unconditionally write whatever it should be.