From: Hyeonggon Yoo <42.hyeyoo@gmail•com>
To: Vlastimil Babka <vbabka@suse•cz>
Cc: akpm@linux-foundation•org, iamjoonsoo.kim@lge•com,
rientjes@google•com, penberg@kernel•org, cl@linux•com,
linux-mm@kvack•org, linux-kernel@vger•kernel.org,
nathan@kernel•org, naresh.kamboju@linaro•org,
clang-built-linux@googlegroups•com, linux-next@vger•kernel.org,
ndesaulniers@google•com, lkft-triage@lists•linaro.org,
sfr@canb•auug.org.au, arnd@arndb•de,
Marco Elver <elver@google•com>
Subject: Re: [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time
Date: Sun, 16 May 2021 06:56:47 +0900 [thread overview]
Message-ID: <20210515215647.GA61684@hyeyoo> (raw)
In-Reply-To: <41c65455-a35b-3ad3-54f9-49ca7105bfa9@suse.cz>
On Sat, May 15, 2021 at 11:24:25PM +0200, Vlastimil Babka wrote:
>
> That's a misunderstanding. __kmalloc() is not a dummy function, you
> probably found only the header declaration.
>
Sorry, that was totally my misunderstanding.
I was reading dummy function in arch/alpha/boot/bootpz.c:415.
I wrongly configured the tool.
> It appears clang 10.0.1 is mistakenly evaluating __builtin_constant_p()
> as true. Probably something to do with LTO, because MAX_OPTINSN_SIZE
> seems it could be a "link-time constant".
That is what I was missing. Thank you for kindly explaining it.
> Maybe we could extend Marco Elver's followup patch that uses
> BUILD_BUG_ON vs BUG() depending on size_is_constant parameter. It could
> use BUG() also if the compiler is LLVM < 11 or something. What would be
> the proper code for this condition?
Fixing clang's bug in linux kernel doesn't seem to be a solution.
So now I understand why Nathan said we might require LLVM > 11.
I thought I should do something to fix it because I sent the patch.
but I was misunderstanding a lot. Thank you sincerely for letting me know.
Thanks,
Hyeonggon
next prev parent reply other threads:[~2021-05-15 21:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210511173448.GA54466@hyeyoo>
2021-05-15 21:09 ` [PATCH v3] mm, slub: change run-time assertion in kmalloc_index() to compile-time Hyeonggon Yoo
2021-05-15 21:24 ` Vlastimil Babka
2021-05-15 21:56 ` Hyeonggon Yoo [this message]
2021-05-16 6:34 ` Nathan Chancellor
2021-05-18 0:38 ` Hyeonggon Yoo
2021-05-18 0:43 ` Nathan Chancellor
2021-05-18 1:53 ` Hyeonggon Yoo
2021-05-18 9:28 ` Vlastimil Babka
2021-05-18 11:18 ` Hyeonggon Yoo
2021-05-18 11:34 ` Vlastimil Babka
2021-05-19 5:45 ` Hyeonggon Yoo
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