tree 7ef31abd6fccdb387691f400720ca19e4ae51c63
parent 232ffe4e03d92e08b8d564b23856155b31492619
author Hao Jiang <jianghao@google.com> 1613959245 -0800
committer Hao Jiang <jianghao@google.com> 1614893543 -0800

Bug fix: pidControlLoop may loop infinitely.

boost::basic_waitable_timer::cancel is a non-blocking function and only
sends cancellation to the pending operations. For other operations:
```
If the timer has already expired when cancel() is called, then the
handlers for asynchronous wait operations will:
* have already been invoked; or
* have been queued for invocation in the near future.
These handlers can no longer be cancelled, and therefore are passed an
error code that indicates the successful completion of the wait
operation.
```

In our case, if pidControlLoop() has been invoked or in the invoke
queue while the timer cancellation, it will ignore the cancal ec and
infinitely call the pidControlLoop() chain.

Thus an extra cancel variable is introduced to break the chain.

Signed-off-by: Hao Jiang <jianghao@google.com>
Change-Id: Ie4e53454ee326bdf612abb511990610a6b528300