Re: [PATCH tip/core/rcu 01/13] mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU

From: Paul E. McKenney
Date: Thu Apr 13 2017 - 12:00:46 EST


On Thu, Apr 13, 2017 at 01:06:56PM +0200, Vlastimil Babka wrote:
> 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.

Exactly!

But I must confess that "tombstone" was an excessively obscure word
choice, even for native English speakers. I have reworded as follows:

[ paulmck: Add comments mentioning the old name, as requested by Eric
Dumazet, in order to help people familiar with the old name find
the new one. ]

Does that help?

Thanx, Paul