linux-kernel - Re: [PATCH] init: Initialize jump labels before command line option parsing

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Message-Id: <20190416164418.3ca1d8cef2713a1154067291@linux-foundation.org>
Date:   Tue, 16 Apr 2019 16:44:18 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <groeck@...gle.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Mike Rapoport <rppt@...ux.ibm.com>, linux-mm@...ck.org
Subject: Re: [PATCH] init: Initialize jump labels before command line option
 parsing

On Tue, 16 Apr 2019 13:54:04 -0700 Dan Williams <dan.j.williams@...el.com> wrote:

> When a module option, or core kernel argument, toggles a static-key it
> requires jump labels to be initialized early. While x86, PowerPC, and
> ARM64 arrange for jump_label_init() to be called before parse_args(),
> ARM does not.
> 
>   Kernel command line: rdinit=/sbin/init page_alloc.shuffle=1 panic=-1 console=ttyAMA0,115200 page_alloc.shuffle=1
>   ------------[ cut here ]------------
>   WARNING: CPU: 0 PID: 0 at ./include/linux/jump_label.h:303
>   page_alloc_shuffle+0x12c/0x1ac
>   static_key_enable(): static key 'page_alloc_shuffle_key+0x0/0x4' used
>   before call to jump_label_init()
>   Modules linked in:
>   CPU: 0 PID: 0 Comm: swapper Not tainted
>   5.1.0-rc4-next-20190410-00003-g3367c36ce744 #1
>   Hardware name: ARM Integrator/CP (Device Tree)
>   [<c0011c68>] (unwind_backtrace) from [<c000ec48>] (show_stack+0x10/0x18)
>   [<c000ec48>] (show_stack) from [<c07e9710>] (dump_stack+0x18/0x24)
>   [<c07e9710>] (dump_stack) from [<c001bb1c>] (__warn+0xe0/0x108)
>   [<c001bb1c>] (__warn) from [<c001bb88>] (warn_slowpath_fmt+0x44/0x6c)
>   [<c001bb88>] (warn_slowpath_fmt) from [<c0b0c4a8>]
>   (page_alloc_shuffle+0x12c/0x1ac)
>   [<c0b0c4a8>] (page_alloc_shuffle) from [<c0b0c550>] (shuffle_store+0x28/0x48)
>   [<c0b0c550>] (shuffle_store) from [<c003e6a0>] (parse_args+0x1f4/0x350)
>   [<c003e6a0>] (parse_args) from [<c0ac3c00>] (start_kernel+0x1c0/0x488)
> 
> Move the fallback call to jump_label_init() to occur before
> parse_args(). The redundant calls to jump_label_init() in other archs
> are left intact in case they have static key toggling use cases that are
> even earlier than option parsing.

Has it been confirmed that this fixes
mm-shuffle-initial-free-memory-to-improve-memory-side-cache-utilization.patch
on beaglebone-black?