Re: [PATCH 3/4] hash: fix rw concurrency while moving keys

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

> >-----Original Message-----
> >[Wang, Yipeng] I was thinking about another corner case and wondering
> >if the version counter needs to be done on key deletion as well.
> >For example, a reader reads out the index and falsely matches a
> >signature, before it reads out the data and the key, the key-data pair
> >got deleted, removed, and recycled by another writer thread.  This
> >writer partially overwrote the key (because key store is too large to be
> atomic).
> >Now, the reader begins to compare the key, and accidentally matches the
> >key (because the key is partially written and accidentally matches),
> >will The reader read the wrong data out (which should have been a lookup
> miss)?
> >
> [Wang, Yipeng] As a second thought after reading your slides, I think the
> scenario I described above should be handled by the upper level application
> using RCU-like mechanisms to recycle key-data only after the grace period.
> So I think it is OK. Please ignore my last comment.
> 
> But if convenient, please add more comment in the API doc and in user
> guide as well just in case users might not understand the restriction.
> 
Agree, it needs careful documentation. I plan to change the documentation after the patch is completed.

> Thanks
> Yipeng