[libvirt] [PATCH v5 3/3] libvirtd: fix crash on termination

[Nikolay Shirokovskiy]

On 14.12.2017 15:31, John Ferlan wrote:
> 
> 
> On 12/14/2017 06:58 AM, Nikolay Shirokovskiy wrote:
>> Hi, all.
>>
>> I looked over thread for this particular patch again and found resolution is we:
>>
>> 1. make a more sane cleanup order in libvirtd's main function (already done by [1]).
>> 2. rewrite linked series [2] by introducing event loop closing callback (ok)
>>
>> But there is no resolution on this patch itself if I am not mistaken and
>> it is not pushed too.
>>
>> LINKS
>>
>> [1] [PATCH 0/5] libvirtd: Adjustments to startup and cleanup processing
>> https://www.redhat.com/archives/libvir-list/2017-November/msg00293.html
> 
> The cover letter of this essentially states the cleanup is an
> alternative based upon the review of "this" series' 3/3 patch (IOW: this
> patch).

Sorry, somehow I lost this impornant notice on my read. I thought [1]
was more about valueable but unrelated to this patch cleanup.

> 
> So I agree w/ Erik - the (last) memory strand that I have left on this
> indicates that the virHashRemoveAll isn't necessary in virNetDaemonClose
> because we've properly order the cleanup with the new patch 4 from [1].

Unfortunately it is not and looks like patch 4 is not pushed too. Anyway
it can't help finishing RPC threads in rigth order to hypervisor drivers
cleanup.

> 
>>
>> [2] [PATCH 0/4] libvirtd: fix hang on termination in qemu driver
>> https://www.redhat.com/archives/libvir-list/2017-October/msg01134.html
>>
> 
> I responded to this series' cover letter with:
> 
> https://www.redhat.com/archives/libvir-list/2017-November/msg00455.html
> 
> in order to attempt to move the conversations found in "this" series to
> that series rather than clouding "this" series with information
> belonging to that series.
> 
> So the question *now* is - did you find a condition/case with [1]
> patches applied, but [2] patches not applied (IOW: current top) where
> something isn't being Unref'd properly?

In a sense yes - virStateCleanup is still called before RPC threads are joined
which causes crashes. It is not fixed by [1].

Nikolay

> 
> John
> 
>>
>> Nikolay
>>
>> On 30.10.2017 14:14, John Ferlan wrote:
>>> From: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>
>>>
>>> The problem is incorrect order of qemu driver shutdown and shutdown
>>> of netserver threads that serve client requests (thru qemu driver
>>> particularly).
>>>
>>> Net server threads are shutdown upon dispose which is triggered
>>> by last daemon object unref at the end of main function. At the same
>>> time qemu driver is shutdown earlier in virStateCleanup. As a result
>>> netserver threads see invalid driver object in the middle of request
>>> processing.
>>>
>>> Let's move shutting down netserver threads earlier to virNetDaemonClose.
>>>
>>> Note: order of last daemon unref and virStateCleanup
>>> is introduced in 85c3a182 for a valid reason.
>>>
>>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>>> ---
>>>  src/rpc/virnetdaemon.c | 1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/src/rpc/virnetdaemon.c b/src/rpc/virnetdaemon.c
>>> index 8c21414897..33bd8e3b06 100644
>>> --- a/src/rpc/virnetdaemon.c
>>> +++ b/src/rpc/virnetdaemon.c
>>> @@ -881,6 +881,7 @@ virNetDaemonClose(virNetDaemonPtr dmn)
>>>      virObjectLock(dmn);
>>>  
>>>      virHashForEach(dmn->servers, daemonServerClose, NULL);
>>> +    virHashRemoveAll(dmn->servers);
>>>  
>>>      virObjectUnlock(dmn);
>>>  }
>>>