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From: Sven Eckelmann <sven@narfation.org>
To: b.a.t.m.a.n@lists.open-mesh.org
Subject: [B.A.T.M.A.N.] Reordered rcu refcounting
Date: Sun, 30 Jan 2011 02:52:55 +0100	[thread overview]
Message-ID: <1296352379-1546-1-git-send-email-sven@narfation.org> (raw)

Hi,

I told Linus and Marek that the implementation of some datastructures using
reference counting and RCUs must be redesigned. The problem is that call_rcu
should only be used when the reference count is zero because multiple call_rcu
cannot be initiated at the same time. The next problem is that we may try to
access an element with the refcount 0 when we try to traverse a rcu protected
list. This problem cannot be solved by kref - thus we have to use atomic_t
again to _not_ increase the reference count when it was already zero.

Marek asked me what we must change - I try to summarize those things in the
following patches. They aren't tested and should only be seen as suggestions
what must be done to finish the "remove orig_hash lock"-patches.

If you try these patches then please keep in mind that they will sell your soul
to the next confectioner (for some cookies or a pie).

More information can be found inside Documentation/RCU/rcuref.txt

Btw, maybe I've found a bug inside the find_router with enabled bonding (see
"BUG" in patch 4).

Best regards,
	Sven

             reply	other threads:[~2011-01-30  1:52 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-30  1:52 Sven Eckelmann [this message]
2011-01-30  1:52 ` [B.A.T.M.A.N.] [PATCH 1/4] batman-adv: Correct rcu refcounting for gw_node Sven Eckelmann
2011-02-02 17:37   ` [B.A.T.M.A.N.] [PATCH] " Linus Lüssing
2011-02-02 19:49     ` Marek Lindner
2011-02-02 20:43       ` Linus Lüssing
2011-02-02 21:42     ` Sven Eckelmann
2011-02-03  0:19       ` Marek Lindner
2011-02-03  9:55       ` Linus Lüssing
2011-02-03 10:01         ` Sven Eckelmann
2011-02-03 14:43     ` [B.A.T.M.A.N.] [PATCH 1/3] " Linus Lüssing
2011-02-03 17:56       ` Sven Eckelmann
2011-02-03 14:43     ` [B.A.T.M.A.N.] [PATCH 2/3] batman-adv: add __rcu annotations " Linus Lüssing
2011-02-03 14:43     ` [B.A.T.M.A.N.] [PATCH 3/3] batman-adv: Increase orig_node refcount before releasing rcu read lock Linus Lüssing
2011-01-30  1:52 ` [B.A.T.M.A.N.] [PATCH 2/4] batman-adv: Correct rcu refcounting for softif_neigh Sven Eckelmann
2011-01-30  1:52 ` [B.A.T.M.A.N.] [PATCH 3/4] batman-adv: Correct rcu refcounting for batman_if Sven Eckelmann
2011-01-30  1:52 ` [B.A.T.M.A.N.] [PATCH 4/4] batman-adv: Correct rcu refcounting for neigh_node Sven Eckelmann
2011-01-30 15:20   ` [B.A.T.M.A.N.] [PATCHv2 " Sven Eckelmann
2011-02-03 17:02 ` [B.A.T.M.A.N.] Reordered rcu refcounting Marek Lindner
2011-02-03 17:03   ` [B.A.T.M.A.N.] [PATCH 1/4] batman-adv: Correct rcu refcounting for gw_node Marek Lindner
2011-02-03 17:03   ` [B.A.T.M.A.N.] [PATCH 2/4] batman-adv: Correct rcu refcounting for softif_neigh Marek Lindner
2011-02-03 17:03   ` [B.A.T.M.A.N.] [PATCH 3/4] batman-adv: Correct rcu refcounting for batman_if Marek Lindner
2011-02-03 17:03   ` [B.A.T.M.A.N.] [PATCH 4/4] batman-adv: Correct rcu refcounting for neigh_node Marek Lindner
2011-02-04 12:59     ` [B.A.T.M.A.N.] [PATCHv2 " Marek Lindner
2011-02-04 15:21   ` [B.A.T.M.A.N.] Reordered rcu refcounting, v3 Linus Lüssing
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 1/7] batman-adv: Correct rcu refcounting for gw_node Linus Lüssing
2011-02-10 11:01     ` Linus Lüssing
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 2/7] batman-adv: Correct rcu refcounting for softif_neigh Linus Lüssing
2011-02-10 12:45     ` Linus Lüssing
2011-02-10 13:57       ` Marek Lindner
2011-02-12 21:23         ` Linus Lüssing
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 3/7] batman-adv: Correct rcu refcounting for batman_if Linus Lüssing
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 4/7] batman-adv: Correct rcu refcounting for neigh_node Linus Lüssing
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 5/7] batman-adv: Make bat_priv->curr_gw an rcu protected pointer Linus Lüssing
2011-02-08 13:18     ` Marek Lindner
2011-02-10 10:42       ` Linus Lüssing
2011-02-10 14:25         ` Marek Lindner
2011-02-12 21:21           ` Linus Lüssing
2011-02-12 21:21           ` [B.A.T.M.A.N.] [PATCHv2 " Linus Lüssing
2011-02-13 21:09             ` Marek Lindner
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 6/7] batman-adv: add __rcu annotations for gw_node Linus Lüssing
2011-02-13 21:10     ` Marek Lindner
2011-02-04 15:21   ` [B.A.T.M.A.N.] [PATCH 7/7] batman-adv: Increase orig_node refcount before releasing rcu read lock Linus Lüssing
2011-02-04 16:33     ` [B.A.T.M.A.N.] [PATCHv2 " Linus Lüssing
2011-02-13 21:11     ` [B.A.T.M.A.N.] [PATCH " Marek Lindner

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