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From: David Vrabel <david.vrabel@citrix.com>
To: David Vrabel <david.vrabel@citrix.com>, Jan Beulich <JBeulich@suse.com>
Cc: Juergen Gross <JGross@suse.com>,
	xen-devel@lists.xenproject.org, boris.ostrovsky@oracle.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] xenbus: don't bail early from xenbus_dev_request_and_reply()
Date: Thu, 7 Jul 2016 14:22:27 +0100	[thread overview]
Message-ID: <577E5793.5030209__25350.5882960328$1467897814$gmane$org@citrix.com> (raw)
In-Reply-To: <577E5565.40302@citrix.com>

On 07/07/16 14:13, David Vrabel wrote:
> On 07/07/16 13:23, Jan Beulich wrote:
>>>>> On 07.07.16 at 14:17, <david.vrabel@citrix.com> wrote:
>>> On 07/07/16 13:09, Jan Beulich wrote:
>>>>>>> On 07.07.16 at 13:36, <david.vrabel@citrix.com> wrote:
>>>>> On 07/07/16 08:32, Jan Beulich wrote:
>>>>>> We must not skip the transaction_end() call for a failed
>>>>>> XS_TRANSACTION_START. The removed code fragment got introduced by
>>>>>> commit 027bd7e899 ("xen/xenbus: Avoid synchronous wait on XenBus
>>>>>> stalling shutdown/restart") without its description really indicating
>>>>>> why it was added (and hence I can't identify whether a more complex
>>>>>> change might be needed here).
>>>>>
>>>>> If sending the XS_TRANSACTION_END message failed, then the transaction
>>>>> is still open and transaction_end() should not be called.
>>>>>
>>>>> However, if sending an XS_TRANSACTION_START failed, then
>>>>> transaction_end() should be called.
>>>>>
>>>>> So, yes a more complex fix is needed here.
>>>>
>>>> Well, both of the things you name are what happens with the patch
>>>> in place. So if those two conditions are all that needs to be satisfied,
>>>> then no more complex change is needed afaict (and was the behavior
>>>> before the cross referenced commit) - the question really is whether
>>>> that other commit meant to deal with something _beyond_ those two
>>>> things.
>>>
>>> You call transaction_end() if msg->type == XS_TRANSACTION_END, even if
>>> xb_write() returned an error.
>>
>> When xb_write() returns an error, msg->type gets set to XS_ERROR.
> 
> So?
> 
> 	if ((msg->type == XS_TRANSACTION_END) ||
> 	    (...))
> 		transaction_end();
> 
> We don't check msg->type for XS_TRANSACTION_END messages.

Sorry, being stupid.  Yeah, the change is fine but it needs a better
commit message.

David

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  parent reply	other threads:[~2016-07-07 13:22 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-07  7:25 [PATCH 0/2] xenbus: xenbus_dev_request_and_reply() adjustments Jan Beulich
2016-07-07  7:32 ` [PATCH 1/2] xenbus: don't bail early from xenbus_dev_request_and_reply() Jan Beulich
2016-07-07  7:32 ` [PATCH 2/2] xenbus: simplify xenbus_dev_request_and_reply() Jan Beulich
     [not found] ` <577E219402000078000FBDB6@prv-mh.provo.novell.com>
2016-07-07 11:36   ` [PATCH 1/2] xenbus: don't bail early from xenbus_dev_request_and_reply() David Vrabel
     [not found]   ` <577E3ED0.906@citrix.com>
2016-07-07 12:09     ` Jan Beulich
     [not found]     ` <577E629C02000078000FC32F@prv-mh.provo.novell.com>
2016-07-07 12:17       ` David Vrabel
     [not found]       ` <577E4865.1080307@citrix.com>
2016-07-07 12:23         ` Jan Beulich
     [not found]         ` <577E65CB02000078000FC35B@prv-mh.provo.novell.com>
2016-07-07 13:13           ` David Vrabel
     [not found]           ` <577E5565.40302@citrix.com>
2016-07-07 13:22             ` David Vrabel [this message]
     [not found]             ` <577E5793.5030209@citrix.com>
2016-07-07 13:35               ` Jan Beulich
2016-07-08 10:18                 ` David Vrabel
2016-07-08 10:56 ` [PATCH 0/2] xenbus: xenbus_dev_request_and_reply() adjustments David Vrabel

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