bhyve: monitor: forward SIGTERM to the VM process

[novel]

Summary

Currently, sending SIGTERM to the bhyve process triggers ACPI poweroff
for a VM. However, when running bhyve in monitor mode (-M), there are
two processes: the monitor process and the actual VM process. Sending
SIGTERM to the VM process works as before -- it powers off the VM.
But sending SIGTERM to the monitor process just kills the monitor process,
leaving the stale VM process running.

Thus, forward the SIGTERM signal from the monitor process to the
VM process for consistency.

[markj]

Thanks, I've run into this problem too.

Rather than forwarding signals, why not have a pipe shared between the two processes? The child process can use it to detect when the parent goes away, and exit automatically. That should be simpler and will work for all cases where the parent exits (assertion failure, SIGKILL, etc.).

[bnovkov]

In D58788#1348916, @markj wrote:

Thanks, I've run into this problem too.

Rather than forwarding signals, why not have a pipe shared between the two processes? The child process can use it to detect when the parent goes away, and exit automatically. That should be simpler and will work for all cases where the parent exits (assertion failure, SIGKILL, etc.).

+1 for this approach, it's more robust than forwarding signals. I was planning to implement this pipe-based fix soon, but if you have the time and will to do so please go for it!

[novel]

In D58788#1348937, @bnovkov wrote:

In D58788#1348916, @markj wrote:

Thanks, I've run into this problem too.

Rather than forwarding signals, why not have a pipe shared between the two processes? The child process can use it to detect when the parent goes away, and exit automatically. That should be simpler and will work for all cases where the parent exits (assertion failure, SIGKILL, etc.).

+1 for this approach, it's more robust than forwarding signals. I was planning to implement this pipe-based fix soon, but if you have the time and will to do so please go for it!

Pipe is a good idea, I didn't think about that. Will try to implement it, thanks.

[novel]

Re-implement monitoring using a pipe.

[markj]

Looks good, thanks. The review title and description are stale now, I presume you will fix them before pushing.