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    SubjectRe: [net-next-2.6 PATCH RFC] TCPCT part 1d: generate Responder Cookie
    William Allen Simpson a écrit :
    > Eric Dumazet wrote:
    >> This patch looks fine, but I dont see how this new function is used.
    >> Some points :
    >> 1) We are working hard to remove rwlocks from network stack, so please
    >> dont
    >> add a new one. You probably can use a seqlock or RCU, or a server
    >> handling 10.000 connections request per second on many NIC will hit
    >> this rwlock.
    > This is my attempt at using RCU, as seqlock didn't seem to apply (and is
    > missing any Documentation.)

    That seems very good, thanks, we can sort out details later, when full picture
    is available.

    > After the discussion about context, one question that I have is the need
    > for the _bh suffix?
    > + rcu_read_lock_bh();
    > + memcpy(&xvp->cookie_bakery[0],
    > + &rcu_dereference(tcp_secret_generating)->secrets[0],
    > + sizeof(tcp_secret_generating->secrets));
    > + rcu_read_unlock_bh();

    Well, you dont need to disable BH in this code running in softirq context only.

    Just use rcu_read_lock() (like you use spin_lock() in same function/context)

    > Documentation/RCU/checklist.txt #7 says:
    > One exception to this rule: rcu_read_lock() and rcu_read_unlock()
    > may be substituted for rcu_read_lock_bh() and rcu_read_unlock_bh()
    > in cases where local bottom halves are already known to be
    > disabled, for example, in irq or softirq context. Commenting
    > such cases is a must, of course! And the jury is still out on
    > whether the increased speed is worth it.

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      Last update: 2009-11-04 00:05    [W:0.022 / U:13.500 seconds]
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