Re: [Qemu-devel] [PATCH 3/8] RunState: Add additional states

[Jan Kiszka <jan.kiszka@web.de>]

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On 2011-09-01 20:39, Luiz Capitulino wrote:
> On Thu, 01 Sep 2011 20:30:57 +0200
> Jan Kiszka <jan.kiszka@siemens.com> wrote:
> 
>> On 2011-09-01 20:12, Luiz Capitulino wrote:
>>> Currently, only vm_start() and vm_stop() change the VM state.
>>> That's, the state is only changed when starting or stopping the VM.
>>>
>>> This commit adds the runstate_set() function, which makes it possible
>>> to also do state transitions when the VM is stopped or running.
>>>
>>> Additional states are also added and the current state is stored.
>>>
>>> Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
>>> ---
>>>  cpus.c      |    1 +
>>>  migration.c |    8 +++++++-
>>>  sysemu.h    |   10 +++++++++-
>>>  vl.c        |   20 ++++++++++++++++++++
>>>  4 files changed, 37 insertions(+), 2 deletions(-)
>>>
>>
>> ...
>>
>>> diff --git a/vl.c b/vl.c
>>> index f0b56a4..59f71fc 100644
>>> --- a/vl.c
>>> +++ b/vl.c
>>> @@ -321,6 +321,22 @@ static int default_driver_check(QemuOpts *opts, void *opaque)
>>>  }
>>>  
>>>  /***********************************************************/
>>> +/* QEMU state */
>>> +
>>> +static RunState current_run_state = RSTATE_NO_STATE;
>>> +
>>> +bool runstate_check(RunState state)
>>> +{
>>> +    return current_run_state == state;
>>> +}
>>> +
>>> +void runstate_set(RunState state)
>>> +{
>>> +    assert(state < RSTATE_MAX);
>>> +    current_run_state = state;
>>
>> I still think this should check for valid state transitions instead of
>> blindly accepting what the caller passes in.
> 
> I thought your comment where more like a future enhancement than
> a request for change.

I think we want this now to document at a central place which
transitions are valid and which not. State machines without such checks
break sooner or later, subtly.

> 
> What to do if the transition is invalid? abort()?

Yes.

Jan


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