linux-kernel - Re: [Xen-devel] [PATCH 3/3 v2] xen/xenbus: Improve failure processing code for __xenbus_switch

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Message-ID: <542047EA.6090202@citrix.com>
Date:	Mon, 22 Sep 2014 17:01:46 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Chen Gang <gang.chen.5i5j@...il.com>
CC:	<konrad.wilk@...cle.com>, <boris.ostrovsky@...cle.com>,
	<stefano.stabellini@...citrix.com>, <mukesh.rathor@...cle.com>,
	<xen-devel@...ts.xenproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/3 v2] xen/xenbus: Improve failure processing
 code for __xenbus_switch_state()

On 22/09/14 16:51, Chen Gang wrote:
> On 09/22/2014 11:04 PM, David Vrabel wrote:
>> On 18/09/14 15:01, Chen Gang wrote:
>>> When failure occurs, need return failure code instead of 0, or some of
>>> indirect upper callers may misunderstand.
>>>
>>> e.g. in "block/xen-blkback/xenbus.c":
>>>
>>>     connect() -> xenbus_switch_state() -> __xenbus_switch_state().
>>
>> Can you make xenbus_switch_state() void?  The callers don't need to do
>> any error handling.
>>
> 
> After "grep rn xenbus_switch_state *" under "drivers/", it is not one
> place to check the return value of xenbus_switch_state(), and also it
> is export to outside for individual modules.
> 
> So we need change many subsystems for it, and also need face the rick
> for incompatible with the old individual modules which source code are
> not in upstream.

Having to update 9 callers doesn't seem like much work.

> And are you sure the caller need not notice about it, when it really
> fails? (for me, I guess they need notice about it)

Yes.  xenbus_switch_state() already signals the fatal error to the
toolstack with xenbus_dev_fatal().

David
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