Bug 80594

Summary:	event loop test fails from time to time
Product:	Wayland	Reporter:	Marek Chalupa <mchqwerty>
Component:	wayland	Assignee:	Wayland bug list <wayland-bugs>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	medium
Version:	unspecified
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:
Attachments:	Add asserts, fix indentation Sleep 15ms before entering epoll_wait Add asserts, fix indentation

Description Marek Chalupa 2014-06-27 12:29:26 UTC

Hi,

it's very rare event, I noticed it by accident, so I tried this:

  $ while ./event-loop-test; do ; done

Sometimes it takes time, but the result is:

test "event_loop_destroy":      exit status 0, pass.
lt-event-loop-test: tests/event-loop-test.c:258: event_loop_timer_updates: Assertion `context.count == 2' failed.
test "event_loop_timer_updates":        signal 6, fail.
test "event_loop_timer":        exit status 0, pass.
test "event_loop_signal":       exit status 0, pass.
test "event_loop_free_source_with_data":        exit status 0, pass.
test "event_loop_post_dispatch_check":  exit status 0, pass.
6 tests, 5 pass, 1 fail

I tried it on fedora and arch linux, master branch of wayland.

Regards,
Marek Chalupa

Comment 1 Marek Chalupa 2014-08-19 10:30:15 UTC

Hi,

looked a little bit into it. This occasional failure is caused by epoll_wait catching only one timer source. Since we have not guaranteed that both timers will expire exactly at the same time, it may happen that epoll_wait will return
before the later timer expires, having only one fd ready.

The best fix IMO (tried) would be to add getter for source's fd and poll on the fd until it's ready for reading. This way we could wait for both timers to expire before calling wl_event_loop_dispatch. This would require change in libwayland, though.

The solution I therefore chose is just simply sleep a while before entering the epoll_wait, so that we are "sure" that both timers expired.

Along with the patch solving this, I'm attaching patch that adds some asserts into this test and fixes wrong indentation.

Cheers,
Marek

Comment 2 Marek Chalupa 2014-08-19 10:31:14 UTC

Created attachment 104879 [details] [review]
Add asserts, fix indentation

Comment 3 Marek Chalupa 2014-08-19 10:32:26 UTC

Created attachment 104880 [details] [review]
Sleep 15ms before entering epoll_wait

Comment 4 Marek Chalupa 2014-08-19 10:35:39 UTC

Created attachment 104881 [details] [review]
Add asserts, fix indentation

Oops, seems like loading the patch failed. This is the same patch loaded again.

Comment 5 Pekka Paalanen 2014-08-19 11:38:54 UTC

Both patches pushed.

commit b24fa4c8216e3f0f7b644c7b8c6949925f19ada9
Author: Marek Chalupa <mchqwerty@gmail.com>
Date:   Tue Aug 19 12:03:48 2014 +0200

    tests: fix event_loop_timer_updates


commit 12ec657014d7fda1c9ebb0358a72bd1a4b5d868c
Author: Marek Chalupa <mchqwerty@gmail.com>
Date:   Tue Aug 19 10:34:52 2014 +0200

    tests: event_loop_timer_updates - add asserts and fix indentation


I assume this fixes the issue.

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