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Re: [libvirt] [PATCH 1/7] Add @seconds vaiable to qemuAgentSend()



On 08/20/2012 02:10 AM, MATSUDA, Daiki wrote:
> (2012/08/16 21:58), Martin Kletzander wrote:
>> On 08/15/2012 03:36 AM, MATSUDA Daiki wrote:
>>>
>>>   Add @seconds variable to qemuAgentSend().
>>>   When @tiemout is true, @seconds controls how long to wait for a
>>> response
>>>   (if @seconds is VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT, default to
>>>   QEMU_AGENT_WAIT_TIME).
>>>   If @timeout is false, @seconds is ignored.
>>>
>>>
>>> Signed-off-by: MATSUDA Daiki <matsudadik intellilink co jp>
>>> ---
>>>   include/libvirt/libvirt-qemu.h |    6 ++++++
>>>   src/qemu/qemu_agent.c          |   30 ++++++++++++++++++++----------
>>>   2 files changed, 26 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/include/libvirt/libvirt-qemu.h
>>> b/include/libvirt/libvirt-qemu.h
>>> index a37f897..013ed5a 100644
>>> --- a/include/libvirt/libvirt-qemu.h
>>> +++ b/include/libvirt/libvirt-qemu.h
>>> @@ -44,6 +44,12 @@ virDomainPtr virDomainQemuAttach(virConnectPtr
>>> domain,
>>>                                    unsigned int pid_value,
>>>                                    unsigned int flags);
>>>
>>> +typedef enum {
>>> +    VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK = -2,
>>
>> Correct me if I'm wrong, but isn't this the same as setting timeout to
>> false?
> 
> Yes, it is same that @timeout = false to qemuAgentSend() from
> qemuAgentCommand().
> 
>  
>>> +    VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT = -1,
>>> +    VIR_DOMAIN_QEMU_AGENT_COMMAND_NOWAIT = 0,
>>> +} virDomainQemuAgentCommandTimeoutValues;
>>> +
>>>   # ifdef __cplusplus
>>>   }
>>>   # endif
>>> diff --git a/src/qemu/qemu_agent.c b/src/qemu/qemu_agent.c
>>> index 15af758..26c2726 100644
>>> --- a/src/qemu/qemu_agent.c
>>> +++ b/src/qemu/qemu_agent.c
>>> @@ -837,6 +837,8 @@ void qemuAgentClose(qemuAgentPtr mon)
>>>    * @mon: Monitor
>>>    * @msg: Message
>>>    * @timeout: use timeout?
>>> + * @seconds: timeout seconds. if
>>> VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT and
>>> + *           @timeout is true, use default value.
>>
>> If my previous assumption is correct, than the timeout parameter can be
>> completely thrown away.
> 
> @seconds is effective uder the situation @timeout = true.
> Then @seconds must be > 0. But @seconds = 0, it is dangerous.
> 
> I do not understand whether it is needed, but other people discussed.
> https://www.redhat.com/archives/libvir-list/2012-July/msg00603.html
> 

I don't suggest to change the behavior, I just see that if the parameter
'timeout' is omitted, we can still get all the options to run the
command with (nonblock/timeout/block), so it's just a simplification.

>>>    *
>>>    * Send @msg to agent @mon.
>>>    * Wait max QEMU_AGENT_WAIT_TIME for agent
>>> @@ -848,7 +850,8 @@ void qemuAgentClose(qemuAgentPtr mon)
>>>    */
>>>   static int qemuAgentSend(qemuAgentPtr mon,
>>>                            qemuAgentMessagePtr msg,
>>> -                         bool timeout)
>>> +                         bool timeout,
>>> +                         int seconds)
>>>   {
>>>       int ret = -1;
>>>       unsigned long long now, then = 0;
>>> @@ -864,7 +867,8 @@ static int qemuAgentSend(qemuAgentPtr mon,
>>>       if (timeout) {
>>>           if (virTimeMillisNow(&now) < 0)
>>>               return -1;
>>> -        then = now + QEMU_AGENT_WAIT_TIME;
>>> +        then = now + (seconds ==
>>> VIR_DOMAIN_QEMU_AGENT_COMMAND_DEFAULT ?
>>> +                      QEMU_AGENT_WAIT_TIME : seconds * 1000ull);
>>>       }
>>
>> Also if seconds == VIR_DOMAIN_QEMU_AGENT_COMMAND_BLOCK, then this causes
>> 'then' to be smaller than now. I'm not sure what that would do with
>> pthread_cond_timedwait, but that's definitely not wanted behavior.
> 
> Its situation is blocked on calling qemuAgentSend() from
> qemuAgentCommand().
> But qemuAgentSend() may also have the block code.
> 

OK, you're right. It is blocked when the qemuAgentSend is called. It
still looks unclean to me, though, because of the redundant option. It'd
be great to have another opinion from someone else :)

Martin


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