Re: [tipc-discussion] Questions about broadcast link link reset.

[jason <huz...@gm...>]

Hi Allan,

Thanks for the information!

2011/3/23 Stephens, Allan <all...@wi...>

> Jason wrote:
>
> > When sending say a NAME_DISTRIBUTOR message through broadcast
> > pseudo link and reach the queue limits(which is 3000), the following call
> > graph can
> > happen:
> >
> > tipc_bclink_send_msg(buf) -> tipc_link_send_buf (bcl,buf) ->
> > tipc_link_reset(bcl) -> ...  (I produce it by decrease the queue limit)
> >
> >
> > My questions are:
> > 1) Why we call tipc_link_reset if importance is greater than
> > CONN_MANAGER?
> > Can you point me the background knowledge?
>
> Jon may be in a better position to answer this question, since this logic
> pre-dates my involvement with TIPC. However, I believe the idea here is that
> TIPC is capable of surviving situations in which an application's payload
> message cannot be sent due to link congestion, but not an inability to send
> an "internal" message (such as a name distributor or fragmentation message).
> That is, TIPC can tell an application to wait and retry sending a payload
> message later, but it cannot tell itself to wait and resend its own internal
> messages. Consequently, when a non-payload message can't be sent TIPC resets
> the link to try and clear the congestion (which should really be happening
> in the first place).
>
> > 2) Why not hold the tipc_node_lock while access the pseudo link/node like
> > other paths such as tipc_bclink_recv_pkt  do?
>
> When a message is sent over the broadcast link TIPC takes the bc_lock to do
> the job that taking tipc_node_lock() does for normal unicast links.
>
> > Yours,
> > jason
>
> I should also point out that the code you are looking at was enhanced in
> TIPC 1.7.7 to allow TIPC to survive the situation in which a name
> distribution message can't be sent because of link congestion. This means
> that TIPC no longer attempts to reset the broadcast link if it can't send a
> name distribution message.
>
> Regards,
> Al
>
>


-- 
Yours,
jason