Re: [lwip-devel] pbuf.c issues

[Leon Woestenberg]

Hi all,

Christiaan Simons wrote:
> Hi,
>
> * Can anyone explain the idea behind the
> double locking in pbuf_pool_alloc() ??
>
> I see both SYS_ARCH_PROTECT() macro's
> and some pbuf.c local flags like pbuf_pool_alloc_lock
> and pbuf_pool_free_lock.
>
> I figured the pbuf.c local flags are only used
> when SYS_LIGHTWEIGHT_PROT == 0,
>   
The thing I remember is that SYS_LIGHTWEIGHT_PROT was introduced to make 
an Ethernet driver interrupt handler able to pbuf_pool_alloc()
pbufs for incoming traffic, in a single threaded system (i.e. a 
non-blocking mutex approach between interrupt code and application code).

I have run a "cvs blame" or rather "cvs annotate" on the code and the 
pbuf_pool_alloc_* stuff seems to be from David Haas, but I am not sure if
he implemented it or only touched-up the code.

It goes back to 2003-02. The mailing list might help:

http://lists.gnu.org/archive/html/lwip-members/2003-02/index.html

Regards,

Leon.