From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] scsi: fix race condition when removing target
Date: Wed, 29 Nov 2017 17:34:21 +0100
Message-ID: <20171129163421.GA32495@lst.de>
References: <20171129030556.47833-1-yanaijie@huawei.com> <1511973108.3222.10.camel@linux.vnet.ibm.com>
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To: James Bottomley <jejb@linux.vnet.ibm.com>
Cc: Jason Yan <yanaijie@huawei.com>, martin.petersen@oracle.com, linux-scsi@vger.kernel.org, Hannes Reinecke <hare@suse.de>, Christoph Hellwig <hch@lst.de>, Johannes Thumshirn <jthumshirn@suse.de>, Zhaohongjiang <zhaohongjiang@huawei.com>, Miao Xie <miaoxie@huawei.com>

On Wed, Nov 29, 2017 at 08:31:48AM -0800, James Bottomley wrote:
> This analysis fails here: get_device() on something with refcount 0
> returns NULL.  That triggers the if clause to ignore this device.

No, it doesn't.  Take a look at the get_device and kobject_get
implementations,