From: Vlastimil Babka <vbabka@suse.cz>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>,
Matthew Wilcox <willy@infradead.org>
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported
Date: Tue, 11 May 2021 10:33:04 +0200 [thread overview]
Message-ID: <cfd5ad12-e589-dcca-52da-6b9db3e26b12@suse.cz> (raw)
In-Reply-To: <20210511030343.GB98904@hyeyoo>
On 5/11/21 5:03 AM, Hyeonggon Yoo wrote:
> On Mon, May 10, 2021 at 04:44:09PM +0100, Matthew Wilcox wrote:
>> On Tue, May 11, 2021 at 12:02:30AM +0900, Hyeonggon Yoo wrote:
>> > @@ -382,8 +385,8 @@ static __always_inline unsigned int kmalloc_index(size_t size)
>> > if (size <= 8 * 1024 * 1024) return 23;
>> > if (size <= 16 * 1024 * 1024) return 24;
>> > if (size <= 32 * 1024 * 1024) return 25;
>> > - if (size <= 64 * 1024 * 1024) return 26;
>> > - BUG();
>> > +
>> > + BUILD_BUG_ON_MSG(1, "unexpected size in kmalloc_index()");
>>
>> we're being encouraged to use static_assert() these days.
>> https://en.cppreference.com/w/c/language/_Static_assert
>>
>
> can you tell me difference between static_assert and BUILD_BUG_ON?
> it seems that mm subsystem does not make use of it now.
Some difference is explained in include/linux/build_bug.h near static_assert
definition.
But importantly it seems it's not possible to place static_assert(false) in
place of the BUG() because it will trigger despite not being reachable.
BUILD_BUG_ON_MSG(1 "..."); worked as expected for me.
prev parent reply other threads:[~2021-05-11 8:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-08 22:13 [PATCH] mm: kmalloc_index: remove case when size is more than 32MB Hyeonggon Yoo
2021-05-08 23:19 ` Matthew Wilcox
2021-05-09 5:33 ` Hyeonggon Yoo
2021-05-10 10:09 ` Vlastimil Babka
2021-05-10 13:58 ` Hyeonggon Yoo
2021-05-10 14:04 ` Vlastimil Babka
2021-05-10 15:02 ` [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported Hyeonggon Yoo
2021-05-10 15:15 ` Christoph Lameter
2021-05-10 15:21 ` Vlastimil Babka
2021-05-11 3:09 ` Hyeonggon Yoo
2021-05-10 15:19 ` Vlastimil Babka
2021-05-10 15:38 ` Hyeonggon Yoo
2021-05-11 8:36 ` Vlastimil Babka
2021-05-11 8:37 ` Vlastimil Babka
2021-05-11 9:14 ` Hyeonggon Yoo
2021-05-11 2:59 ` [PATCH v3] mm: change run-time assertion in kmalloc_index() to compile-time Hyeonggon Yoo
2021-05-10 15:44 ` [PATCH v2] mm: kmalloc_index: make compiler break when size is not supported Matthew Wilcox
2021-05-11 3:03 ` Hyeonggon Yoo
2021-05-11 8:33 ` Vlastimil Babka [this message]
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