NetBSD Problem Report #52112

From www@NetBSD.org  Mon Mar 27 16:03:58 2017
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Message-Id: <20170327160357.2ABEF7A2B6@mollari.NetBSD.org>
Date: Mon, 27 Mar 2017 16:03:57 +0000 (UTC)
From: dcb314@hotmail.com
Reply-To: dcb314@hotmail.com
To: gnats-bugs@NetBSD.org
Subject: arch/xen/xenbus/xenbus_dev.c:400: pointless assignment in critical section 
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>Number:         52112
>Category:       port-xen
>Synopsis:       arch/xen/xenbus/xenbus_dev.c:400: pointless assignment in critical section
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    port-xen-maintainer
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Mar 27 16:05:00 +0000 2017
>Closed-Date:    Mon Mar 27 18:40:49 +0000 2017
>Last-Modified:  Mon Mar 27 18:40:49 +0000 2017
>Originator:     David Binderman
>Release:        cvs-20170327
>Organization:
>Environment:
>Description:
src/sys/arch/xen/xenbus/xenbus_dev.c:395] -> [src/sys/arch/xen/xenbus/xenbus_dev.c:400]: (style) Variable 'u' is reassigned a value before the old one has been used.

Source code is

    struct xenbus_dev_data *u = kfs->kfs_v;
    struct xenbus_dev_lwp *xlwp;
    struct xenbus_dev_transaction *trans;

    mutex_enter(&xenbus_dev_open_mtx);
    u = kfs->kfs_v;

Second assignment looks pointless. Suggest remove. 
>How-To-Repeat:

>Fix:

>Release-Note:

>Audit-Trail:
From: Manuel Bouyer <bouyer@antioche.eu.org>
To: gnats-bugs@NetBSD.org
Cc: port-xen-maintainer@netbsd.org, gnats-admin@netbsd.org,
        netbsd-bugs@netbsd.org
Subject: Re: port-xen/52112: arch/xen/xenbus/xenbus_dev.c:400: pointless
 assignment in critical section
Date: Mon, 27 Mar 2017 18:13:26 +0200

 On Mon, Mar 27, 2017 at 04:05:00PM +0000, dcb314@hotmail.com wrote:
 > src/sys/arch/xen/xenbus/xenbus_dev.c:395] -> [src/sys/arch/xen/xenbus/xenbus_dev.c:400]: (style) Variable 'u' is reassigned a value before the old one has been used.
 > 
 > Source code is
 > 
 >     struct xenbus_dev_data *u = kfs->kfs_v;
 >     struct xenbus_dev_lwp *xlwp;
 >     struct xenbus_dev_transaction *trans;
 > 
 >     mutex_enter(&xenbus_dev_open_mtx);
 >     u = kfs->kfs_v;
 > 
 > Second assignment looks pointless. Suggest remove. 

 Actually it's the first one that should be removed. The xenbus_dev_open_mtx
 mutex protects kfs. Maybe kfs assignement should be moved under the
 mutex too.
 Will look and fix later today

 -- 
 Manuel Bouyer <bouyer@antioche.eu.org>
      NetBSD: 26 ans d'experience feront toujours la difference
 --

From: "Manuel Bouyer" <bouyer@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/52112 CVS commit: src/sys/arch/xen/xenbus
Date: Mon, 27 Mar 2017 18:39:55 +0000

 Module Name:	src
 Committed By:	bouyer
 Date:		Mon Mar 27 18:39:55 UTC 2017

 Modified Files:
 	src/sys/arch/xen/xenbus: xenbus_dev.c

 Log Message:
 Avoid variable reassignement; reported by dcb314@hotmail.com in
 PR port-xen/52112


 To generate a diff of this commit:
 cvs rdiff -u -r1.13 -r1.14 src/sys/arch/xen/xenbus/xenbus_dev.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

State-Changed-From-To: open->closed
State-Changed-By: bouyer@NetBSD.org
State-Changed-When: Mon, 27 Mar 2017 18:40:49 +0000
State-Changed-Why:
Fix commited


>Unformatted:

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