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

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Date:   Wed, 25 Jan 2017 14:35:56 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Johannes Weiner <hannes@...xchg.org>, 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 Wed, Jan 25, 2017 at 10:26:08PM +0100, Vlastimil Babka wrote:
> 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>

Thank you both!  I have added these, as well as a Not-acked-by
for Eric.  ;-)

							Thanx, Paul

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