linux-kernel - Re: [PATCH] jump_label: Fix usage in module _

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Date:   Wed, 16 Dec 2020 10:36:13 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Dexuan Cui <decui@...rosoft.com>, Ingo Molnar <mingo@...nel.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        jeyu@...nel.org, ardb@...nel.org
Subject: Re: [PATCH] jump_label: Fix usage in module __init

On Wed, Dec 16, 2020 at 02:54:35PM +0100, Peter Zijlstra wrote:
> Subject: jump_label: Fix usage in module __init
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Wed Dec 16 12:21:36 CET 2020
> 
> When the static_key is part of the module, and the module calls
> static_key_inc/enable() from it's __init section *AND* has a
> static_branch_*() user in that very same __init section, things go
> wobbly.
> 
> If the static_key lives outside the module, jump_label_add_module()
> would append this module's sites to the key and jump_label_update()
> would take the static_key_linked() branch and all would be fine.
> 
> If all the sites are outside of __init, then everything will be fine
> too.
> 
> However, when all is aligned just as described above,
> jump_label_update() calls __jump_label_update(.init = false) and we'll
> not update sites in __init text.
> 
> Fixes: 19483677684b ("jump_label: Annotate entries that operate on __init code earlier")
> Reported-by: Dexuan Cui <decui@...rosoft.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Tested-by: Jessica Yu <jeyu@...nel.org>

Acked-by: Josh Poimboeuf <jpoimboe@...hat.com>

-- 
Josh