linux-kernel - Re: + kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch added to -mm tree

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Date:	Mon, 08 Feb 2016 20:33:56 +1100
From:	Michael Ellerman <mpe@...erman.id.au>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>, krinkin.m.u@...il.com,
	mingo@...e.hu, peterz@...radead.org, linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: +
 kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch
 added to -mm tree

On Thu, 2016-02-04 at 16:13 +0300, Andrey Ryabinin wrote:
> On 02/04/2016 12:44 AM, Andrew Morton wrote:
> > Probably lockdep_init() and lockdep_initialized can be done away with now.
>
> Yup, it probably should be folded into your patch, or we could hold this off for 4.6.
>
> From: Andrey Ryabinin <aryabinin@...tuozzo.com>
>
> Subject: kernel/lockdep: eliminate lockdep_init()
>
> Lockdep is initialized at compile time now. Get rid of lockdep_init().
>
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>

> diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
> index ad8c9db..d544fa3 100644
> --- a/arch/powerpc/kernel/setup_32.c
> +++ b/arch/powerpc/kernel/setup_32.c
> @@ -114,8 +114,6 @@ extern unsigned int memset_nocache_branch; /* Insn to be replaced by NOP */
>
>  notrace void __init machine_init(u64 dt_ptr)
>  {
> -	lockdep_init();
> -
>  	/* Enable early debugging if any specified (see udbg.h) */
>  	udbg_early_init();
>
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index 5c03a6a..f98be83 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -255,9 +255,6 @@ void __init early_setup(unsigned long dt_ptr)
>  	setup_paca(&boot_paca);
>  	fixup_boot_paca();
>
> -	/* Initialize lockdep early or else spinlocks will blow */
> -	lockdep_init();
> -
>  	/* -------- printk is now safe to use ------- */
>
>  	/* Enable early debugging if any specified (see udbg.h) */

Yes please. That has been a royal pain over the years and is still fragile,
very happy to see the back of it.

Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)

cheers