linux-kernel - Re: [Xen-devel] [PATCH] xen/xenbus: Use 'void' instead of 'int' for the return of xenbus_switch

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Message-ID: <20140929084102.GE28628@zion.uk.xensource.com>
Date:	Mon, 29 Sep 2014 09:41:51 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	Chen Gang <gang.chen.5i5j@...il.com>, <konrad.wilk@...cle.com>,
	<ian.campbell@...rix.com>, <wei.liu2@...rix.com>,
	<boris.ostrovsky@...cle.com>, <bhelgaas@...gle.com>,
	<jgross@...e.com>, <yongjun_wei@...ndmicro.com.cn>,
	<mukesh.rathor@...cle.com>, <xen-devel@...ts.xenproject.org>,
	<linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<linux-scsi@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH] xen/xenbus: Use 'void' instead of 'int' for
 the return of xenbus_switch_state()

On Fri, Sep 26, 2014 at 07:07:19PM +0100, David Vrabel wrote:
> On 26/09/14 17:36, Chen Gang wrote:
> > When xenbus_switch_state() fails, it will call xenbus_switch_fatal()
> > internally, so need not return any status value, then use 'void' instead
> > of 'int' for xenbus_switch_state() and __xenbus_switch_state().
> > 
> > Also need be sure that all callers which check the return value must let
> > 'err' be 0.
> 
> I've rewritten the commit message as:
> 
>     xen/xenbus: don't return errors from xenbus_switch_state()
> 
>     Most users of xenbus_switch_state() weren't handling the failure of
>     xenbus_switch_state() correctly.  They either called
>     xenbus_dev_fatal() (which xenbus_switch_state() has effectively
>     already tried to do), or ignored errors.
> 
>     xenbus_switch_state() may fail because:
> 
>     a) The device is being unplugged by the toolstack. The device will
>     shortly be removed and the error does not need to be handled.
> 
>     b) Xenstore is broken.  There isn't much the driver can do in this
>     case since xenstore is required to signal failure to the toolstack.
> 
>     So, don't report any errors from xenbus_switch_state() which removes
>     some unnecessary error handling in some of the drivers.
> 
> I'd appreciate a review from some of the other front/backend driver
> maintainers on whether this is sensible reasoning.
> 

Looks reasonable to me.

Wei.
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