[lwip-users] Assertion on Select

[Sandra Gilge]

Hi,

regarding my Problem with the assertion on select:
I'm using the IP stack in several tasks (Webserver, SIP, mDNS, TFTP,
MODBUS). 
But every task uses its own sockets. Still there seems to be a problem with
multithreading.
The problem occurs (sporadically) in one task, when another socket is closed
in another task.

It seems that the error NEVER occurs, when SO_REUSE is disabled. (mDNS for
example uses SO_REUSEADDR, so I enabled it recently)
Could it be that the socket is reused before it is really closed and the
select_waiting is set to zero (by doing the new connection) but there is one
more select (by the just closed connection)?

I'm still hoping for answers.

Best regards,
Sandra



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[mailto:address@hidden Im Auftrag von
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Gesendet: Mittwoch, 22. Juli 2015 18:00
An: address@hidden
Betreff: lwip-users Digest, Vol 143, Issue 16

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Today's Topics:

   1. Assertion on select (Sandra Gilge)
   2. Re: lwip-users Digest, Vol 143, Issue 10 (Xun Chen)


----------------------------------------------------------------------

Message: 1
Date: Wed, 22 Jul 2015 14:11:04 +0200
From: "Sandra Gilge" <address@hidden>
To: <address@hidden>
Subject: [lwip-users] Assertion on select
Message-ID: <address@hidden>
Content-Type: text/plain; charset="us-ascii"

Hallo

 

I'm using LWIP 1.4.1 and the Blackfin VDK port from analog devices (which is
originally for 1.4.0). I moved on to 1.4.1 on my own.

 

Now I'm having problems with following assertion when calling select.

LWIP_ASSERT("sock->select_waiting >= 0", sock->select_waiting >= 0);

 

I have several threads that use the socket interface. For me it looks like a
thread safety problem, but SYS_ARCH_PROTECT is implemented.

 

Has anybody a hint what could go wrong?

 

Best Regards,

Sandra

 

 

 

 

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Message: 2
Date: Wed, 22 Jul 2015 09:41:56 -0400
From: Xun Chen <address@hidden>
To: address@hidden
Subject: Re: [lwip-users] lwip-users Digest, Vol 143, Issue 10
Message-ID: <address@hidden>
Content-Type: text/plain; charset=windows-1252; format=flowed

Hi Sergio,

I took your suggestion of only sending out more data in tcp_sent callbak and
rewrite the codes

And I run into another problem: The data stream is very jerky (I am
streaming 200kb/s)

So I used a scope to see how often the tcp_sent callback is invoked, it
turns out:

I will get about 10-20 callbacks within a short burst of 5 to 10ms, then
there is NO callback for 200ms, then repeat

I tried to tune lwip based on various previous suggestions on the forum and
didn't have much luck.

With this callback frequency, it is impossible to plot data in real time
smoothly (data acquisition application)

Any suggestion? Thanks!

Chen

On 7/11/2015 12:00 PM, address@hidden wrote:
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>     1. Re: Retransmit too quick? (Sergio R. Caprile)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 10 Jul 2015 13:31:37 -0300
> From: "Sergio R. Caprile" <address@hidden>
> To: address@hidden
> Subject: Re: [lwip-users] Retransmit too quick?
> Message-ID: <address@hidden>
> Content-Type: text/plain; charset=utf-8
>
> The RAW API is event driven code.
> The ACK is handled as an ACK by lwIP. This means the window is 
> updated, the sent pbufs are freed, and you can send data again.
> You can't send more data until you receive an ACK for your window size.
> You can't queue more data until lwIP frees pbus (when you receive an ACK).
> There is no point in calling the send function when you don't have 
> room to queue/send more data, this causes CPU hog.
> There is no point in calling the send function at specific intervals 
> (assuming you need to send a big bunch of data); if the ACK gets 
> received in between the interval, you'll have dead times where nothing 
> is sent.
> The write time to call the send function is when the sent callback is
fired.
> You are free to choose and write your app the way you want; but, if it 
> does not work and you ask for help...
> Good luck.
>




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