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

[Jonathan Larmour]

Follow-up Comment #11, bug #1902 (project lwip):

I think most systems use free-running timers for clocks where possible. I
think you have to assume the OS clock is accurate - what else can you do!

I would mention here that the lwip internal thread is not the only one that
uses timeouts, other than applications. So does the PPP thread. Also
lwip_select() relies on semaphore waits with timeouts.

But there is one thing that from people's comments here I'm not sure is well
known..... timeouts are meant to be per-thread. They are not global. If a
timeout is set, its callback should only be by that same thread, not any
thread. All this talk about thread safety makes me think that some people are
allowing their ports to have timeout functions called by any thread.


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