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SubjectRe: Q: sock output serialization


>>>>> "kuznet" == kuznet <> writes:

>> when sk->lock.users!=0. Is there a particular reason why such
>> task queue does not exist?

kuznet> Because it appeared to be useless overhead. I also
kuznet> believed that it will be required in tcp, but one day I
kuznet> understood that all the problems of these kind
kuznet> dissolved. 8)

Yes, probably, this should also hold for other protocols. I need to study the
protocol specs for further details.

But I realized another problem X.25 related SMP problem -- this time
related to input. The protocol design assumes that the transmission
path preserves the packet ordering. It seems that with 2.4.0 SMP, the ordering
of the packets when received from the wire is not necessarily the same
as when delivered to the protocolŽs receive method. Is this true?

LAPB should be able to recover from such sequence errors. But the X.25 packet
layer can only detect such problem (and reset the connection). It cannot
recover from such errors transparently. Unfortunatly, the current design
assumes that the LAPB layer is performed below the network interface.

Although this allows to support controllers which implement LAPB in firmware,
this seems to break the assumptions made by upper layers. The upper layer
assumes that LAPB devices provide a reliable datalink service. But the Linux
network interfaces do not preserve such reliable semantics. (Network
interfaces may drop frames, e.g. when NET_RX input queue overruns, and
and on SMP packet sequencing might change),


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