linux-kernel - Re: [RFC PATCH v2 10/20] jump_label,module: Don't alloc static_key_mod for __ro_after

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Date:   Sat, 29 Jul 2023 00:04:26 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Valentin Schneider <vschneid@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, kvm@...r.kernel.org, linux-mm@...ck.org,
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        Yair Podemsky <ypodemsk@...hat.com>
Subject: Re: [RFC PATCH v2 10/20] jump_label,module: Don't alloc
 static_key_mod for __ro_after_init keys

On Thu, Jul 20, 2023 at 05:30:46PM +0100, Valentin Schneider wrote:
> From: Peter Zijlstra <peterz@...radead.org>
> 
> When a static_key is marked ro_after_init, its state will never change
> (after init), therefore jump_label_update() will never need to iterate
> the entries, and thus module load won't actually need to track this --
> avoiding the static_key::next write.
> 
> Therefore, mark these keys such that jump_label_add_module() might
> recognise them and avoid the modification.
> 
> Use the special state: 'static_key_linked(key) && !static_key_mod(key)'
> to denote such keys.
> 
> Link: http://lore.kernel.org/r/20230705204142.GB2813335@hirez.programming.kicks-ass.net
> NOT-Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Valentin Schneider <vschneid@...hat.com>
> ---
> @Peter: I've barely touched this patch, it's just been writing a comment
> and fixing benign compilation issues, so credit's all yours really!

Ah, it works? Excellent! You can remove the NOT from the SoB then ;-)