From: Marek Lindner <lindner_marek@yahoo.de>
To: The list for a Better Approach To Mobile Ad-hoc Networking
<b.a.t.m.a.n@lists.open-mesh.org>
Subject: Re: [B.A.T.M.A.N.] NDP patches v4
Date: Wed, 5 Jan 2011 13:12:33 +0100 [thread overview]
Message-ID: <201101051312.34513.lindner_marek@yahoo.de> (raw)
In-Reply-To: <1293810385-31761-1-git-send-email-linus.luessing@ascom.ch>
Hi Linus,
great that you embraced the feedback that quickly. As discussed in Berlin I'll
go through your patches once I have a little bit more room to manoeuvre (next
week is rather packed).
> Would be great if someone could check the usage of rcu-locking +
> refcounting. I was also a little confused because in
> "Documentation/RCU/listRCU.txt" list_del_rcu() and list_add_rcu() are not
> protected with a spinlock for the list here, but in the batman-adv code we
> are usually having those extra locks. Do I have to leave those spinlocks
> or can I remove them for adding/deleting entries in the neigh_list?
I don't understand why you think there are no locks. Did you read the text
around the examples (Documentation/RCU/listRCU.txt) ? I mean, below the first
example (which indeed does not contain spinlocks) it is written:
Normally, the write_lock() and write_unlock() would be replaced by
a spin_lock() and a spin_unlock(), but in this case, all callers hold
audit_netlink_sem, so no additional locking is required. The auditsc_lock
can therefore be eliminated, since use of RCU eliminates the need for
writers to exclude readers. Normally, the write_lock() calls would
be converted into spin_lock() calls.
If you check the following example you'll find spinlocks or search for
list_del_rcu() in the kernel sources to find more usage scenarios.
Regards,
Marek
next prev parent reply other threads:[~2011-01-05 12:12 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-31 15:46 [B.A.T.M.A.N.] NDP patches v4 Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 01/10] batman-adv: Rename packet type / structure / functions for OGMs Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 02/10] batman-adv: Adding workqueue for new ndp packets Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 03/10] batman-adv: Send neighbor discovery packets Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 04/10] batman-adv: Creating neighbor structures, updating LQs Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 05/10] batman-adv: Purge outdated ndp neighbours Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 06/10] batman-adv: Adding ndp debugfs output Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 07/10] batman-adv: Adding batman_if specific sysfs wrapper macros for UINT Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 08/10] batman-adv: Adding sysfs parameter for ndp interval Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 09/10] batman-adv: Use local tq values determined by NDP on OGMs Linus Lüssing
2010-12-31 15:46 ` [B.A.T.M.A.N.] [PATCH 10/10] batman-adv: Use rcu locking + ref-counting for neigh_list Linus Lüssing
2011-01-02 1:27 ` Linus Lüssing
2011-01-05 12:12 ` Marek Lindner [this message]
2011-01-12 15:32 ` [B.A.T.M.A.N.] NDP patches v4 Linus Lüssing
2011-01-12 15:48 ` [B.A.T.M.A.N.] NDP patches v4y Andrew Lunn
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