uv_loop_close() after uv_run() fails

[David Davidović]

Sorry if this a stupid question and shows my failure of grasping the basic concepts but I feel completely lost. So I have a watchdog timer whose job is to check every 30 seconds if there is a global kill switch flag set for the daemon, and if there is, it calls uv_stop() on the loop. (I understand I could just exit() from there but I like to keep valgrind happy at the end of program execution while debugging.) uv_run() returns after that, but when I try calling uv_loop_close() it returns UV_BUSY, and subsequent calls to uv_loop_delete() try the same and bomb with a SIGABRT because of an assertion failure. I'm not sure as to how this could happen, shouldn't uv_run() returning imply that the loop is done processing all of its data? Maybe if libuv runs its own threadpool somewhere, is there any way I can join on these threads as they could be the cause of the problem? How should I safely and successfully terminate the loop in such a condition?

TIA!

[Fedor Indutny]

Heya!

Excerpt from a documentation about `uv_stop()`:

/*
* This function will stop the event loop by forcing uv_run to end
* as soon as possible, but not sooner than the next loop iteration.
* If this function was called before blocking for i/o, the loop won't
* block for i/o on this iteration.
*/

So the `uv_stop()` is forcing `uv_run()` to return, even if there are still
some active handles on the loop. You should close all of them before attempting
to call `uv_loop_close()`, and you could do while walking through all active
handles in loop:

/*
* Walk the list of open handles.
*/
UV_EXTERN void uv_walk(uv_loop_t* loop, uv_walk_cb walk_cb, void* arg);

Cheers,
Fedor.

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[Saúl Ibarra Corretgé]

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See Fedor's response. Here is some code you could adapt to your needs:
https://github.com/joyent/libuv/blob/master/test/task.h#L221-L231


Cheers,

- --
Saúl Ibarra Corretgé
bettercallsaghul.com

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[David Davidović]

Thanks for the speedy replies! I was under the impression that uv_run magically closes its handles when it returns. Didn't really think that one through :)

Cheers,
David