Serial port communication become broken once vm was paused and then unpaused

[icegood]

Steps to reproduce: 1) Establish serial communication between host and guest 2) Pause vm 3) Unpause it back. Expected result: communication will not break Actual result: communication is broken and reopening of com ports on both host and guest lead to nothing. additionally in vm log you can find next messages:

00:01:51.916503 HostSerial#0: Wait failed with error VERR_INVALID_PARAMETER; terminating the worker thread.
00:01:51.916514 PDMThread: Thread 'SerRecv' (0000000009c84840) quit unexpectedly with rc=VERR_INVALID_PARAMETER.
00:01:51.916550 HostSerial#1: Wait failed with error VERR_INVALID_PARAMETER; terminating the worker thread.
00:01:51.916559 PDMThread: Thread 'SerRecv' (0000000009c7f6b0) quit unexpectedly with rc=VERR_INVALID_PARAMETER.

[Mihai Hanor]

I can't reproduce it, VirtualBox 5.2.19 r125117, on Windows 10, running Debian testing as guest.

[icegood]

Issue is perfectly reproducible in 5.2.20 r125813, same host and guest. However i found that COM query from guest to host is OK, but answer from host to guest is not delivered. Log during operation is empty, after shutdown of guest the same lines appear:

00:03:21.457031 Changing the VM state from 'RUNNING' to 'SUSPENDING'
00:03:21.463231 AIOMgr: Endpoint for file '...' (flags 000c0781) created successfully
00:03:21.527568 PDMR3Suspend: 70 495 314 ns run time
00:03:21.527595 Changing the VM state from 'SUSPENDING' to 'SUSPENDED'
00:03:21.527604 Console: Machine state changed to 'Paused'
00:03:24.552684 Changing the VM state from 'SUSPENDED' to 'RESUMING'
00:03:24.552985 AIOMgr: Endpoint for file '...' (flags 000c0723) created successfully
00:03:24.554752 HostSerial#1: Wait failed with error VERR_INVALID_PARAMETER; terminating the worker thread.
00:03:24.554774 HostSerial#0: Wait failed with error VERR_INVALID_PARAMETER; terminating the worker thread.
00:03:24.554784 Changing the VM state from 'RESUMING' to 'RUNNING'

[Mihai Hanor]

Please attach a complete VM log.

[aeichner]

No complete VBox.log attached and there where huge changes in the serial port code afterwards. The issue could be fixed, if not please reopen and attached complete VBox.log this time.