From: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
To: Stephen Hemminger <shemminger@osdl.org>
Cc: David Miller <davem@davemloft.net>, netdev@vger.kernel.org
Subject: Re: [PATCH 4/6] net neighbour: convert to RCU
Date: Wed, 30 Aug 2006 03:21:26 +0400 [thread overview]
Message-ID: <20060829232126.GA18636@ms2.inr.ac.ru> (raw)
In-Reply-To: <20060829160022.552d46e0@dxpl.pdx.osdl.net>
Hello!
> This should not be any more racy than the existing code.
Existing code is not racy.
Critical place is interpretation of refcnt==1. Current code assumes,
that when refcnt=1 and entry is in hash table, nobody can take this
entry (table is locked). So, it can be unlinked from the table.
See? __neigh_lookup()/__neigh_lookup_errno() _MUST_ return alive
and hashed entry. And will stay hashed until the reference is held.
Or until neigh entry is forced for destruction by device going down,
in this case referring dst entries will die as well.
If dst cache grabs an entry, which is purged from table because for some
time it had refcnt==1, you got a valid dst entry referring to dead
neighbour entry.
Alexey
next prev parent reply other threads:[~2006-08-29 23:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-28 23:07 [PATCH 0/6] Lockless neighbour table Stephen Hemminger
2006-08-28 23:07 ` [PATCH 1/6] net neighbor: convert top level list to RCU Stephen Hemminger
2006-08-28 23:07 ` [PATCH 2/6] neighbour: convert neighbour hash table to hlist Stephen Hemminger
2006-08-28 23:07 ` [PATCH 3/6] neighbour: convert pneigh " Stephen Hemminger
2006-08-28 23:07 ` [PATCH 4/6] net neighbour: convert to RCU Stephen Hemminger
2006-08-29 15:28 ` Alexey Kuznetsov
2006-08-29 18:22 ` Stephen Hemminger
2006-08-29 18:34 ` Martin Josefsson
2006-08-29 20:17 ` Stephen Hemminger
2006-08-29 21:17 ` Alexey Kuznetsov
2006-08-29 21:46 ` Stephen Hemminger
2006-08-29 22:16 ` Alexey Kuznetsov
2006-08-29 23:00 ` Stephen Hemminger
2006-08-29 23:21 ` Alexey Kuznetsov [this message]
2006-08-29 23:49 ` Stephen Hemminger
2006-08-30 0:06 ` Alexey Kuznetsov
2006-08-29 23:36 ` Alexey Kuznetsov
2006-08-28 23:07 ` [PATCH 5/6] neighbour: convert lookup to sequence lock Stephen Hemminger
2006-08-28 23:07 ` [PATCH 6/6] neighbour: convert hard header cache to sequence number Stephen Hemminger
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