linux-kernel - Re: [PATCH RFC] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY

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Message-ID: <a4cb93f8-0ca4-57aa-f395-1b22143a32bd@suse.cz>
Date:   Wed, 25 Jan 2017 22:26:08 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Johannes Weiner <hannes@...xchg.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org
Subject: Re: [PATCH RFC] mm: Rename SLAB_DESTROY_BY_RCU to
 SLAB_TYPESAFE_BY_RCU

On 01/25/2017 09:25 PM, Johannes Weiner wrote:
> On Wed, Jan 18, 2017 at 03:07:32AM -0800, Paul E. McKenney wrote:
>> A group of Linux kernel hackers reported chasing a bug that resulted
>> from their assumption that SLAB_DESTROY_BY_RCU provided an existence
>> guarantee, that is, that no block from such a slab would be reallocated
>> during an RCU read-side critical section.  Of course, that is not the
>> case.  Instead, SLAB_DESTROY_BY_RCU only prevents freeing of an entire
>> slab of blocks.
>>
>> However, there is a phrase for this, namely "type safety".  This commit
>> therefore renames SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU in order
>> to avoid future instances of this sort of confusion.
>>
>> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
>
> This has come up in the past, and it always proved hard to agree on a
> better name for it. But I like SLAB_TYPESAFE_BY_RCU the best out of
> all proposals, and it's much more poignant than the current name.

Heh, until I've seen this thread I had the same wrong assumption about the flag, 
so it suprised me. Good thing I didn't have a chance to use it wrongly so far :)

"Type safety" in this context seems quite counter-intuitive for me, as I've only 
heard it to describe programming languages. But that's fine when the name sounds 
so exotic that one has to look up what it does. Much safer than when the meaning 
seems obvious, but in fact it's misleading.

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> Acked-by: Johannes Weiner <hannes@...xchg.org>
>
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