linux-kernel - Re: [PATCH tip/core/rcu 01/13] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY

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Message-ID: <50d59b9c-fa8e-1992-2613-e84774ec5428@suse.cz>
Date:   Thu, 13 Apr 2017 13:06:56 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, bobby.prani@...il.com,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org
Subject: Re: [PATCH tip/core/rcu 01/13] mm: Rename SLAB_DESTROY_BY_RCU to
 SLAB_TYPESAFE_BY_RCU

On 04/13/2017 11:12 AM, Peter Zijlstra wrote:
> On Wed, Apr 12, 2017 at 09:55:37AM -0700, 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.
> 
> And that while we wrote a huge honking comment right along with it...
> 
>> [ paulmck: Add "tombstone" comments as requested by Eric Dumazet. ]
> 
> I cannot find any occurrence of "tomb" or "TOMB" in the actual patch,
> confused?

It's the comments such as:

+ * Note that SLAB_TYPESAFE_BY_RCU was originally named SLAB_DESTROY_BY_RCU.

so that people who remember the old name can git grep its fate.

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