[dpdk-dev] [PATCH] hash: document breakage with multi-writer thread

Stephen Hemminger stephen at networkplumber.org
Thu Jun 4 19:58:17 CEST 2020


On Thu, 4 Jun 2020 17:51:43 +0000
Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com> wrote:

> <snip>
> 
> > Subject: [PATCH] hash: document breakage with multi-writer thread
> > 
> > The code in rte_cuckoo_hash multi-writer support is broken if write
> > operations are called from a non-EAL thread.
> > 
> > rte_lcore_id() wil return LCORE_ID_ANY (UINT32_MAX) for non EAL thread
> > and that leads to using wrong local cache.
> > 
> > Add error checks and document the restriction.  
> Having multiple non-EAL writer threads is a valid use case. Should we fix the issue instead?

Discovered this the hard way...

Fixing is non-trivial. Basically, the local cache has to be take out and
that leads to having to do real locking or atomic operations.


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