You forgot about this again in the next sentence. :-)
RENTRANCY PROTECTION! If does not matter _how_ they run, it matters what
context they preempt and what that context has to make to prevent that
preemption. If you still do not get the point, make
sed -e 's/local_bh_/local_irq_/'
over net/* and kill softirqs. Everything will work just fine.
Moreover, if you deal only with a single TCP connection
(and sysctl tcp_low_latency is not set), even hardirq latency will not suck,
all real work is done at process context.
I would not say I understood what you wanted to say. :-)
Does my statement about sed match your view? :-)
What I know is that there is no hairy locking dependencies at all
and there is no magic there. Especially, on level of sockets.
The things, which are troublesome are various shared trees/hash tables
(e.g. socket hash tables), which are modified both by incoming network
packets and process contexts.
I have some obscure suspicion that naive dream of "realtime" folks is
to move all those "bad" things to some kernel threads and to talk
to those threads passing some messages. I hope this suspicion is wrong,
otherwise I would say: go to Mach, pals. :-(
Alexey
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