Re: [Qemu-block] [PATCH] xen-block: treat XenbusStateUnknown the same as XenbusStateClosed

[John Snow]

On 9/23/19 5:38 AM, Paul Durrant wrote:
>> -----Original Message-----
>> From: John Snow <address@hidden>
>> Sent: 20 September 2019 22:11
>> To: Paul Durrant <address@hidden>; address@hidden; address@hidden;
>> address@hidden
>> Cc: Kevin Wolf <address@hidden>; Stefano Stabellini <address@hidden>; Max 
>> Reitz
>> <address@hidden>; Anthony Perard <address@hidden>; Mark Syms <address@hidden>
>> Subject: Re: [Qemu-block] [PATCH] xen-block: treat XenbusStateUnknown the 
>> same as XenbusStateClosed
>>
>>
>>
>> On 9/18/19 7:57 AM, Paul Durrant wrote:
>>> When a frontend gracefully disconnects from an offline backend, it will
>>> set its own state to XenbusStateClosed. The code in xen-block.c correctly
>>> deals with this and sets the backend into XenbusStateClosed. Unfortunately
>>> it is possible for toolstack to actually delete the frontend area
>>> before the state key has been read, leading to an apparent frontend state
>>> of XenbusStateUnknown. This prevents the backend state from transitioning
>>> to XenbusStateClosed and hence leaves it limbo.
>>>
>>
>> Does the 0 come from a read into de-allocated memory?
> 
> No, it comes from the fact that the xenstore state key is not present. 
> Conventionally a missing state key means the state is reported as 
> XenbusStateUnknown.
> 
>   Paul
> 

Good enough for me, just had to confirm.

Reviewed-by: John Snow <address@hidden>