[lwip-devel] [bug #1902] Timeouts and semaphores/mailboxes are too tightly integrated

[Simon Goldschmidt]

Follow-up Comment #12, bug #1902 (project lwip):

>I think you have to assume the OS clock is accurate - what else can you do!

OK, but hooking on the timer tick still can make porting a hard thing.

>I would mention here that the lwip internal thread is not the only one that
uses timeouts, other than applications.

Of course, the only problem is, with the current implementation, internal
timeouts can occur when the stack is not in a state to handle them. And the
easiest solution is to only let timeouts happen when waiting for a message.
Although this does not imply the stack will be in a state to handle timeouts
with future changes, this is OK for now, as the tcpip_thread only pends on an
mbox in its main loop, and the application threads normally don't have
timeouts.

With lwip_select(), it's a different case: it passes a timeout value to
sys_sem_wait_timeout(), but this has nothing to do with lwip timeouts.
lwip_select() does not depend on a function being called while waiting.
Instead, event_callback() is used, which is triggered by receive events of
the stack.

Sadly, this issue is assigned to noone, yet. Also, it could need a comment
from our project leader, since I beleive this to be quit a big step.

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