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

[Goldschmidt Simon]

Uhm, that's exactly what I meant when starting this thread. I just think
the pbuf-pool-code NOT using  SYS_LEIGHTWEIGHT_PROT should be removed
since I discovered it is buggy and wanted to protect other lwip-users
from running into this.

Of course, the SYS_LEIGHTWEIGHT_PROT must not be removed! This would
break the stack!

Simon


> -----Original Message-----
> From: 
> address@hidden
> g 
> [mailto:address@hidden
ongnu.org] On Behalf Of Pettinato, Jim
> Sent: Monday, November 13, 2006 2:55 PM
> To: Mailing list for lwIP users
> Subject: RE: [lwip-users] Bug in pbuf.c regarding PBUF_POOL
> 
> 
> I recall hashing this about previously; again I believe it is 
> required when the OS does not provide a semaphore mechanism 
> to assure the pbuf pool does not get corrupted. Whether a 
> multi-threaded or single-threaded implementation, if the 
> ethif interrupt routine is allocating and moving received 
> packets using pbufs, there has to be a way to prevent that 
> from happening in the middle of a critical section of the 
> stack's code. THIS is why SYS_LIGHTWEIGHT_PROT exists and is needed.
> 
> Read the comments in sys.h for more background... And someone 
> correct me if I'm wrong, but I think this was Adam's original 
> protection scheme and not something 'some programmer' added.
> 
> I am using it and must also vote to retain this code.
> 
> - Jim
> 
> 
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden
>  On Behalf Of Peter Graf
> Sent: Sunday, November 12, 2006 5:25 AM
> To: Mailing list for lwIP users
> Subject: Re: [lwip-users] Bug in pbuf.c regarding PBUF_POOL
> 
> 
> Leon Woestenberg wrote:
> 
> >> Thanks for the detailed post - good to see folks getting to grips 
> >> with the stack.  The above seemed to summarise quite nicely and I 
> >> agree completely with that.
> >>
> > I completely agree with you; It's good to see there is 
> interest in the
> 
> > lwIP stack from developers that are concerned abouts its 
> correctness.
> > 
> > The SYS_LIGHTWEIGHT_PROT protection was introduced by one of the 
> > developers using the stack to protect *ONLY* between 
> interrupt context
> 
> > and single-thread user-space context if I am not mistaken.
> 
> I think you are mistaken.
> 
> > I am all for removing it, because the locking solution does 
> not scale 
> > across different platforms.
> 
> I have to use SYS_LIGHTWEIGHT_PROT in a _multithreaded_ 
> environment with interrupt-triggered device driver. Removing 
> it would render lwIP unusable for me. I guess it lies in the 
> nature of a simple locking mechanism to be platform specific, 
> but that makes it "lightweight".
> 
> I vote against a removal.
> 
> All the best
> Peter
> 
> 
> 
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