Re: [lwip-users] how lwip know internet cable is unplug

[ake . forslund]

Ok, I now I get it.

So protection around my calls it is,
but I don't quite see how RX and TX can be handled in the same thread since
the TX-function is registered with lwip in the netif-structure and RX isn't.


OK I see now that there is an input-pointer
in the netif-structure as well but it's not referenced in the driver-template
(ethernetif.c) so I invented something on my own...I'll have to dig through
the examples one more time and look how they have done it...

/Åke
-----------------------------
Åke Forslund
0433-273296
NIBE AB
Box 14
S-285 21  Markaryd
Tel +46-(0)433-273296

From:	"Simon Goldschmidt" <address@hidden>
To:	Mailing list for lwIP users <address@hidden>
Date:	2011-09-02 14:32
Subject:	Re: [lwip-users] how lwip know internet cable is unplug
Sent by:	address@hidden

---

address@hidden wrote:
> I'm not quite sure what you're suggesting. Is it to put all calls
that may
> change states of netif, dhcp etc. in a single thread or is it the
use of a
> separate thread to handle RX, or something else?

I'm just repeating the mantra that lwIP core code is not thread protected
(with very little exceptions, mostly regarding memory management functions)
and either all code using lwIP functions/variables must be used from one
thread only or you have to protect it yourself (e.g. by using a semaphore
or something like that).

E.g. if you have RX in one thread and TX in another thread, you can be
most sure that you will get problems at some point (e.g. corrupted state,
corrupted pbuf-ref or corrupted lists).

I have to point this out to prevent other users reading this list from
making such a mistake (that can be hard to debug). And your statement "set_link_up/down
looks pretty safe to use from my rx-thread" can sound like these functions
are thread-safe to new users (as it did, to me).

Simon
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