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Date: Mon, 07 May 2012 21:35:07 +0200
From: Matthias Schiffer <mschiffer@universe-factory.net>
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Subject: [B.A.T.M.A.N.] The current state of the batman-adv vis code
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Hi,
after reading Marek's and Sven's comments to my question about the vis
code, and looking at the code a bit I came to the following conclusion
about the first part of the cleanup, the finishing of the RCU conversion
of the vis code:

It should be possible to get rid of the vis_hash_lock altogether, as the
hash table has spinlocks for the hash lists itself; overall hash
consistency might be a issue though - I would propose adding a
hash_update function that updates a hash entry without deleting and
re-adding the hlist node.

I think I found a bug in the hash_add function though. First there is a
RCU-locked loop that checks if a entry does already exist, but the
spinlock is taken after the rcu_read_unlock() - thus allowing the same
entry to be appended twice if two threads try to add it at the same time.=


If you want to contact me about this via IRC, I'm now idling in #batman
- my nickname there is neoraider.

Thanks,
Matthias


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