Re: [PATCH] scsi: fix race condition when removing target

From: "hch@lst.de" <hch@lst.de>
To: Bart Van Assche <Bart.VanAssche@wdc.com>
Cc: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
	"zhaohongjiang@huawei.com" <zhaohongjiang@huawei.com>,
	"jthumshirn@suse.de" <jthumshirn@suse.de>,
	"hch@lst.de" <hch@lst.de>,
	"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
	"hare@suse.de" <hare@suse.de>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"yanaijie@huawei.com" <yanaijie@huawei.com>,
	"jejb@linux.vnet.ibm.com" <jejb@linux.vnet.ibm.com>,
	"miaoxie@huawei.com" <miaoxie@huawei.com>
Subject: Re: [PATCH] scsi: fix race condition when removing target
Date: Wed, 29 Nov 2017 17:20:50 +0100	[thread overview]
Message-ID: <20171129162050.GA32071@lst.de> (raw)
In-Reply-To: <1511972310.2671.7.camel@wdc.com>

On Wed, Nov 29, 2017 at 04:18:30PM +0000, Bart Van Assche wrote:
> As the above patch description shows it can happen that the SCSI core calls
> get_device() after the device reference count has reached zero and before
> the memory for struct device is freed. Although the above patch looks fine
> to me, would you consider it acceptable to modify get_device() such that it
> uses kobject_get_unless_zero() instead of kobject_get()? I'm asking this
> because that change would help to reduce the complexity of the already too
> complicated SCSI core.

I don't think we can just modify get_device, but we can add a new
get_device_unless_zero.  In fact I have an open coded variant of that
in nvme, and was planning to submit one for the current merge window..