Re: [lwip-users] Mailboxes and Semaphores

[address@hidden]

If I remember correctly, there are many places in the stack where your 
simple semaphore can be used (tcpip_thread, netconn semaphores, etc.) 
but there are also other usages where multiple waiting threads have to 
be supported (i.e. locking the heap in mem_malloc). So I guess you are 
right that the generic sys_sem_t must be the multiple-type.

Speaking of deallocation: I also ran lwIP on an OS which didn't support 
this. I ended up in having a preallocated list/array of 
mboxes/semaphores and returning an instance of that list in sys_sem_new().

Simon


Timmy Brolin wrote:
> Hello,
> I have A few questions about LwIP OS requirements..
>
> Our operating system provides two kinds of semaphores. The normal (and
> resource-light) semaphore only allows a single task to block on it at
> any one time. There is also a second type which allows multiple tasks to
> block on it at the same time, but it requires a bit more memory resources.
> Am I correct in assuming that LwIP requires multiple tasks to block on
> the same semaphore? Are there any semaphores in LwIP which could do with
> the simpler semaphore type?
>
> The mailbox system in our operating system is based on the standard
> semaphores, so only one task may block on a mailbox at any one time. Is
> this acceptable for LwIP?
>
> Our OS has a limitation in that semaphores and mailboxes never can be
> deallocated, and I was hoping that the addition of a deallocation
> funtion for semaphores and mailboxes would be enough to get LwIP running
> on our system. I would prefer not having to write a new mailbox system
> as well.. :-)
>
> Regards,
> Timmy Brolin
>
>
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