VZVirtualMachine asserts that it is used on the queue it was created with,
which for tart is the main queue. Since #1262 replaced the unstructured Task
in "tart run"'s SIGUSR2 handler with ErrorReportingTask, that assertion fails:
Task.init carries @_inheritActorContext, but ErrorReportingTask.init did not,
so an operation written inside MainActor-isolated Run.runOnMainThread() is formed
in a nonisolated init and runs on the cooperative pool, not the main queue.
The result is that asking a VM to stop gracefully kills it instead. Sending
SIGUSR2, which #842 hooked to requestStop() for exactly this purpose, crashes
the process:
Thread 1 queue: com.apple.root.default-qos.cooperative
_dispatch_assert_queue_fail
dispatch_assert_queue
-[VZVirtualMachine requestStopWithError:]
closure in Run.runOnMainThread()
closure in ErrorReportingTask.init(_:operation:)
The guest then loses power without a chance to flush, and on a Linux guest
with ext4's default delayed allocation that discards whatever had not been
written back yet. The same applies to the requestStop() in
applicationShouldTerminate(), i.e. closing the window of a VM run with a GUI.
Give the operation the same @_inheritActorContext that Task.init has, so that
wrapping a call in ErrorReportingTask no longer changes where it runs.
Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
