Re: Regression in dtor/input.git/next - flush pending events on clock type change

On Thu, Feb 5, 2015 at 8:28 PM, Benjamin Tissoires
[off-list ref] wrote:

On Feb 5, 2015 7:04 PM, "Dmitry Torokhov" [off-list ref] wrote:

quoted

Hi Benjamin,

On Thu, Feb 05, 2015 at 06:06:29PM -0500, Benjamin Tissoires wrote:

quoted

Hi Anshul,

The commit 0c3e99437a66e4c869c60c2398449e6d98f3a988 in
dtor/input.git/next
tree introduce an interesting regression in libinput. The tests fail :)

Actually, evemu-record and libinput switch the clock to monotonic when
opening an input node, and the first thing that gets queued is a
SYN_DROPPED event.

However, in the libinput test suite, events are the bare minimum, and
most of the tests contain only one event set (one EV_SYN).
When seeing the SYN_DROPPED, the clients are supposed to drain the
events
until the next EV_SYN, and so they are losing the events that came long
after the ioctl call.
And in the end, the test suite does not receive any events.

Removing the evdev_queue_syn_dropped() call in the ioctl handling fixes
the test suite, and Peter suggested that maybe we should queue a
SYN_DROPPED event iff there are events in the queue.

Does the following patch fixe it? But I would like to see libinput
tests more robust.

It does. Thanks for the quick fix.

Regarding libinput tests, I am not sure we could make them more robust in
this situation. The tests rely on uinput to create predetermined kernel
devices, with a known set of events. Usually, we test one feature/previous
bug we already seen in the past per device per test. The mentioned commit
changed the kernel behavior and I think there is no automatic way to detect
that the problem lies in the kernel rather than in the libinput event
processing.

For example, the simplest test creates one mouse, waits for libinput to open
it, sends REL_X, EV_SYN, and ensures that libinput gets the REL_X event.
Without this fix, the event is not seen, so the test fails. Which is right,
because that means that any libinput client will see the first events
dropped. This is not something we want for our users, especially for
keyboards, when the first thing you do is typing your password for example.

Cheers,
Benjamin

Grmbl, sorry for the dup. Re-sending the mail not from the tablet
which can not send the mail in plain text... :(

Cheers,
Benajmin