linux-kernel - Re: [PATCH 2/6] arm64/mm: Enable memory hot remove

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Date:   Thu, 4 Apr 2019 13:58:18 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Robin Murphy <robin.murphy@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, will.deacon@....com,
        catalin.marinas@....com, mhocko@...e.com,
        mgorman@...hsingularity.net, james.morse@....com,
        mark.rutland@....com, cpandya@...eaurora.org,
        arunks@...eaurora.org, dan.j.williams@...el.com,
        logang@...tatee.com, pasha.tatashin@...cle.com, david@...hat.com,
        cai@....pw, Steven Price <steven.price@....com>
Subject: Re: [PATCH 2/6] arm64/mm: Enable memory hot remove

On Thu, Apr 04, 2019 at 11:09:22AM +0530, Anshuman Khandual wrote:
> > Do these need to be __meminit? AFAICS it's effectively redundant with the containing #ifdef, and removal feels like it's inherently a later-than-init thing anyway.
> 
> I was confused here a bit but even X86 does exactly the same. All these functions
> are still labeled __meminit and all wrapped under CONFIG_MEMORY_HOTPLUG. Is there
> any concern to have __meminit here ?

We do not really need it as long as the code is within #ifdef CONFIG_MEMORY_HOTPLUG.
__meminit is being used when functions that are going to be need for hotplug need
to stay around.

/* Used for MEMORY_HOTPLUG */
#define __meminit        __section(.meminit.text) __cold notrace \
                                                  __latent_entropy

#if defined(CONFIG_MEMORY_HOTPLUG)
#define MEM_KEEP(sec)    *(.mem##sec)
#define MEM_DISCARD(sec)
#else
#define MEM_KEEP(sec)
#define MEM_DISCARD(sec) *(.mem##sec)
#endif

So it is kind of redundant to have both.
I will clean it up when reposting [1] and [2].

[1] https://patchwork.kernel.org/patch/10875019/
[2] https://patchwork.kernel.org/patch/10875021/

-- 
Oscar Salvador
SUSE L3