VM eventhandler: Update epoll/kqueue even if the only event is an error

VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

Also avoid sending multiple notifications on an error.

related #24417

R=fschneider@google.com

Committed: https://github.com/dart-lang/sdk/commit/0c3d73967ddaf354ded90f518a1f46e7b1b00774

[zra, 2017-01-25 17:36:54]

Description was changed from

==========
VM eventhandler: Update epoll/kqueue if only event is an error

related #24417
==========

to

==========
VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

related #24417
==========

[zra, 2017-01-25 17:42:02]

Description was changed from

==========
VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

related #24417
==========

to

==========
VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

Also avoid sending multiple notifications on an error.

related #24417
==========

[zra, 2017-01-25 17:43:34]

zra@google.com changed reviewers:
+ rmacnak@google.com

[zra, 2017-01-25 21:16:44]

zra@google.com changed reviewers:
+ fschneider@google.com

[Florian Schneider, 2017-01-25 21:24:55]

Is there a way to reliably test this?

[zra, 2017-01-25 21:29:46]

On 2017/01/25 21:24:55, Florian Schneider wrote:
> Is there a way to reliably test this?

We'd need two isolates or processes, one of which wedges on a sleep() or similar
so that it doesn't respond to isolate messages from the eventhandler, and the
other that causes kqueue/epoll to emit a few messages without an error, and then
one with an error (w/ & w/o other statuses as well).

It would be difficult to ensure that the first isolate sleep()s long enough for
the second isolate to generate all the needed messages, and the resulting test
would likely be very flaky.

[Florian Schneider, 2017-01-25 21:36:35]

Lgtm

[zra, 2017-01-25 21:50:04]

Description was changed from

==========
VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

Also avoid sending multiple notifications on an error.

related #24417
==========

to

==========
VM eventhandler: Update epoll/kqueue even if the only event is an error

Otherwise, we may try to add an fd to epoll/kqueue when it is already
there.

Also avoid sending multiple notifications on an error.

related #24417

R=fschneider@google.com

Committed:
https://github.com/dart-lang/sdk/commit/0c3d73967ddaf354ded90f518a1f46e7b1b00774
==========

[zra, 2017-01-25 21:50:05]

Committed patchset #2 (id:20001) manually as
0c3d73967ddaf354ded90f518a1f46e7b1b00774 (presubmit successful).