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Message-ID: <CAF2d9jhevnUaUt8_0sdffXz6--TcEvtAbMQwwFiZ+Eb0Ms_T5A@mail.gmail.com> Date: Sun, 7 Sep 2014 21:51:15 -0700 From: Mahesh Bandewar <maheshb@...gle.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Nikolay Aleksandrov <nikolay@...hat.com>, Jay Vosburgh <j.vosburgh@...il.com>, Veaceslav Falico <vfalico@...hat.com>, Andy Gospodarek <andy@...yhouse.net>, David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Maciej Zenczykowski <maze@...gle.com> Subject: Re: [PATCH net-next v1 2/2] bonding: Simplify the xmit function for modes that use xmit_hash On Sun, Sep 7, 2014 at 9:41 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > On Sun, 2014-09-07 at 19:23 -0700, Mahesh Bandewar wrote: >> > >> I'm not expecting any writer protection here since all the paths are >> covered with some or the other lock at this moment. Just though that >> performing array manipulation in RCU context would be useful. > > > It is not useful. It is confusing only. > > If you think of RCU as a replacement for reader/writer lock, its obvious > that once you get the writer lock, there is no need to get the reader > lock. > As I had mentioned earlier, simultaneous writers are taken care. The xmit is lockless and was thinking about how not to get the xmit into the scenario where this array manipulation is partially done and that partial value is used by the xmitter and result may not be desirable. Hence thought that rcu-read-lock will protect the xmitter getting into that state. I guess that was incorrect so I'll remove the read-lock/unlock from the code. Thanks for the clarification Eric. > Extract from Documentation/RCU/whatisRCU.txt : > > Use rcu_read_lock() and rcu_read_unlock() to guard RCU > read-side critical sections. > > Use some solid scheme (such as locks or semaphores) to > keep concurrent updates from interfering with each other. > > > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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