Re: [PATCH v5 10/12] python/machine.py: split shutdown into hard and soft flavors

[Philippe Mathieu-Daudé]

On 7/10/20 7:06 AM, John Snow wrote:
> 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>
> ---
>  python/qemu/machine.py | 95 +++++++++++++++++++++++++++++++++++-------
>  1 file changed, 80 insertions(+), 15 deletions(-)
> 

:))

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>