linux-kernel - Re: [PATCH 2/3] tools: testing: Use existing atomic.h for vma/radix-tree tests

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Message-ID: <DCDY7RAG4AN9.1192AMMUC2LMV@google.com>
Date: Thu, 28 Aug 2025 09:20:56 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>, <linux-kernel@...r.kernel.org>, 
	<maple-tree@...ts.infradead.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH 2/3] tools: testing: Use existing atomic.h for
 vma/radix-tree tests

On Thu Aug 28, 2025 at 1:05 AM UTC, Liam R. Howlett wrote:
> * Brendan Jackman <jackmanb@...gle.com> [250827 07:04]:
>> The shared userspace logic used for unit-testing radix-tree and VMA code
>> currently has its own replacements for atomics helpers. This is not
>> needed as the necessary APIs already have userspace implementations in
>> the tools tree. Switching over to that allows deleting a bit of code.
>> 
>> Note that the implementation is different; while the version being
>> deleted here is implemented using liburcu, the existing version in tools
>> uses either x86 asm or compiler builtins. It's assumed that both are
>> equally likely to be correct.
>> 
>> The tools tree's version of atomic_t is a struct type while the version
>> being deleted was just a typedef of an integer. This means it's no
>> longer valid to call __sync_bool_compare_and_swap() directly on it. One
>> option would be to just peek into the struct and call it on the field,
>> but it seems a little cleaner to just use the corresponding atomic.h
>> API. On non-x86 archs this is implemented using
>> __sync_val_compare_and_swap(). It's not clear why the old version uses
>> the bool variant instead of the generic "val" one, for now it's assumed
>> that this was a mistake.
>> 
>> Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
>> ---
>>  tools/testing/shared/linux/maple_tree.h |  6 ++----
>                               ^^^^^
> Did you say radix-tree?
>
> I was going to accept this because I put my code in the same directory,
> but since you'll be respinning..

Yeah, it's only the maple tree tests specifically that are affected. Did
I understand correctly that you're asking me to reword the commit
messages to avoid confusion? If so, yep good idea will do.