[Libevent-users] event_base_loop: wait for events to be added by other threads?

[Evan Jones <evanj@xxxxxxx>]

I am writing a multi-threaded libevent application. Or rather, I am 
retrofitting an existing libevent 1.4 application to contain multiple 
libevent threads. Since the existing code is NOT thread safe, my design 
is basically to partition the application into N pieces, each with its 
own event loop. Then I glue the pieces together by scheduling callbacks 
in appropriate threads using event_active.

There is one small problem: if a thread has no active events, it exits. 
In my case, I want it to block, waiting for another thread to call 
event_active to add an event. I have a patch to libevent that fixes this 
by adding an additional flag to event_base_loop. Is this the "right" 
solution to this problem?

If so, I have another concern: the three current flags to libevent are 
actually mutually exclusive. Eg. If you pass EVLOOP_NONBLOCK, that sort 
of implies EVLOOP_ONCE. Similarly, my new flag is incompatible with 
EVLOOP_NONBLOCK and EVLOOP_ONCE. Does it make sense to assign each one a 
bit? Or should the first two bits of flag be the "loop mode"?

00 = normal; run until no active events
01 = EVLOOP_ONCE; wait until one event is triggered then exit
10 = EVLOOP_NONBLOCK; poll the loop once, run highest priority, then exit
11 = EVLOOP_BLOCK_FOR_EXPLICIT_EXIT; run until there is an explicit exit.

Thanks,

Evan Jones

--
Evan Jones
http://evanjones.ca/
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