linux-kernel - Re: [locking/lockdep] 383776fa75: INFO: trying to register non-static key.

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Date:   Sat, 25 Mar 2017 19:13:44 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        kernel test robot <fengguang.wu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>, LKP <lkp@...org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>, wfg@...ux.intel.com
Subject: Re: [locking/lockdep] 383776fa75:  INFO: trying to register
 non-static key.

On Mon, Mar 20, 2017 at 12:41:08PM +0100, Peter Zijlstra wrote:
> Subject: lockdep: Fix per-cpu static objects
> From: Peter Zijlstra <peterz@...radead.org>
> Date: Mon Mar 20 12:26:55 CET 2017
> 
> Since commit:
> 
>   383776fa7527 ("locking/lockdep: Handle statically initialized PER_CPU locks properly")
> 
> we try to collapse per-cpu locks into a single class by giving them
> all the same key. For this key we choose the canonical address of the
> per-cpu object, which would be the offset into the per-cpu area.
> 
> This has two problems:
> 
>  - there is a case where we run !0 lock->key through static_obj() and
>    expect this to pass; it doesn't for canonical pointers.
> 
>  - 0 is a valid canonical address.
> 
> Cure both issues by redefining the canonical address as the address of
> the per-cpu variable on the boot CPU.
> 
> Since I didn't want to rely on CPU0 being the boot-cpu, or even
> existing at all, track the boot CPU in a variable.
> 
> Fixes: 383776fa7527 ("locking/lockdep: Handle statically initialized PER_CPU locks properly")
> Reported-by: kernel test robot <fengguang.wu@...el.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Tested-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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