using re timers properly when multithreaded

[fAuernigg]

"tmr_start" adds a tmr element to the global tmr list.

re/src/tmr/tmr.c

Line 302 in ae64519

list_insert_before(tmrl, le, &tmr->le, tmr);

Is it safe to call tmr_start from a thread different to the libre main thread?

What happens, if the thread adding an element to the timer list is interrupted by the libre main thread. Could it crash or have other impacts?
Is there a way to lock the tmr list during modification?

[sreimers]

For complex multithread scenarios you can use mqueue.

[cspiel1]

Thanks for this hint! We realized now that:

• tmr_start (and most likely also tmr_cancel) don't have to be thread-safe for baresip. They are only called from re_main thread.
• mqueue supports very handy passing control to the re_main thread. We will use this in our application to pass the tmr_start invocation to the re_main thread.