[lwip-devel] [bug #20021] conn->sem is only signaled one-way

[Jonathan Larmour]

Follow-up Comment #8, bug #20021 (project lwip):

> Is it really good pratice to signal a binary semaphore more 
> than once? 

As per my post on the mailing list, for any systems where posting more than
once is disallowed, we could insist the porter makes it allowed. Within the
port-specific code it is easy for them to prevent it happening, whereas it
would be hard for lwIP to maintain an abstraction that supported the
possibility.

>>Alternatively, you can move the current send buffer test into
>>the tcp/ip thread (so the caller thread effectively always
>>waits, and its up to the tcpip thread to whether it resumes).
> That seems like the best solution. We also would need one
> semaphore less per connection. Only non-blocking mode would be
> slower since it would call into tcpip_thread although there is
> no space. But that's what we have to do with our current 
> (multithreaded) implementation...

Certainly I think this would be the better approach (I should have said
that!).


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