John Snow 193bf1c061 python/machine.py: split shutdown into hard and soft flavors ... This is done primarily to avoid the 'bare except' pattern, which suppresses all exceptions during shutdown and can obscure errors. Replace this with a pattern that isolates the different kind of shutdown paradigms (_hard_shutdown and _soft_shutdown), and a new fallback shutdown handler (_do_shutdown) that gracefully attempts one before the other. This split now also ensures that no matter what happens, _post_shutdown() is always invoked. shutdown() changes in behavior such that if it attempts to do a graceful shutdown and is unable to, it will now always raise an exception to indicate this. This can be avoided by the test writer in three ways: 1. If the VM is expected to have already exited or is in the process of exiting, wait() can be used instead of shutdown() to clean up resources instead. This helps avoid race conditions in shutdown. 2. If a test writer is expecting graceful shutdown to fail, shutdown should be called in a try...except block. 3. If the test writer has no interest in performing a graceful shutdown at all, kill() can be used instead. Handling shutdown in this way makes it much more explicit which type of shutdown we want and allows the library to report problems with this process. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Cleber Rosa <crosa@redhat.com> Tested-by: Cleber Rosa <crosa@redhat.com> Message-Id: <20200710050649.32434-11-jsnow@redhat.com> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>		2020-07-14 22:22:22 +02:00
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qemu	python/machine.py: split shutdown into hard and soft flavors	2020-07-14 22:22:22 +02:00