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

[Simon Goldschmidt]

Follow-up Comment #10, bug #1902 (project lwip):

> BTW, if the OS tick timer isn't accurate, then the
> timestamps, or mailbox timeouts for that matter,
> won't probably be either :)

Hm, if you use a hardware timer to do the timestamp, then the OS probably
still uses the tick for the timeout on mailboxes. BUT: while one call to
sys_arch_mbox_fetch() might be a little too late, the overall time
(timestamp) stays accurate.

In our application, system timer tick is one of the lowest since other
hardware has higher timing accuracy needs. If you only take the system tick
as your time, it will always tick a little slower than the real time (unless
you have a free-running cyclic timer, which we haven't, we have to re-trigger
it in software).

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