Re: [lwip-users] Bug in pbuf.c regarding PBUF_POOL

[Mumtaz Ahmad]

Dear Simons

Thats a better way and i have also used it and created my own sequential
APIs using this locking mechanism .This helped me to get a BSD style socket
api with the approximate performance of raw api .

Mumtaz Ahmad
Network Systems Group


----- Original Message ----- 
From: "Christiaan Simons" <address@hidden>
To: "Mailing list for lwIP users" <address@hidden>
Sent: Friday, November 17, 2006 5:39 PM
Subject: Re: [lwip-users] Bug in pbuf.c regarding PBUF_POOL


> @Jonathan:
>
> > > We have a proven real-time pre-emptive design (even with nested
> > > pre-emptable interrupts) that does not use SYS_LIGHTWEIGHT_PROT but
> uses
> > > the "bottom-half" approach.
> >
> > I would be surprised if it were truly thread-safe given my understanding
> of
> > the current code. Maybe it used to be with different earlier code. But I
> > haven't seen the code for that port.
>
> What we do is truly thread safe,
> since we protect the calls to the _raw-API_.
>
> As Leon said the interrupt top half merely
> wakes a high priority task (bottom half) on eth rx.
>
> This task locks a (uCOS) mutex, copies data from the
> ethernet controller and pushes this into the lwIP stack.
> After lwIP is done we unlock this mutex.
>
> Other tasks accessing to any lwIP structure
> are allowed when the mutex is available.
>
> We completely avoid the lwIP socket or sequential API,
> therefore we don't require the troublesome lwIP
> "protection".
>
> Any finer grained locking would require
> improved thread safety many places in the current
> code as many observed correctly before.
>
> BTW direct pbuf pool access is desirable
> for raw-API applications, such as SNMP.
>
> Christiaan Simons
>
> Hardware Designer
> Axon Digital Design
>
> http://www.axon.tv
>
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