# Re: \[PATCH v2\] lib: fix data race in rhashtable\_rehash\_one

- From: Herbert Xu \<herbert@gondor.apana.org.au\>
- Date: 2015-09-22 15:20:03 
- List: netdev
- Page: https://ratatoskr.run/netdev/2015/09/4581137
- Thread: https://ratatoskr.run/netdev/2015/09/4580805/t.md

```text
Dmitry Vyukov [ref] wrote:
> rhashtable_rehash_one() uses complex logic to update entry->next field,
> after INIT_RHT_NULLS_HEAD and NULLS_MARKER expansion:
> 
> entry->next = 1 | ((base + off) << 1)
> 
> This can be compiled along the lines of:
> 
> entry->next = base + off
> entry->next <<= 1
> entry->next |= 1
> 
> Which will break concurrent readers.
> 
> NULLS value recomputation is not needed here, so just remove
> the complex logic.
> 
> The data race was found with KernelThreadSanitizer (KTSAN).
> 
> Signed-off-by: Dmitry Vyukov <dvyukov@google.com>

Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
-- 
Email: Herbert Xu [ref]
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
```