From mboxrd@z Thu Jan  1 00:00:00 1970
From: Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH] Avoid that SCSI device removal through sysfs triggers a
 deadlock
Date: Thu, 27 Oct 2016 12:36:30 +0300
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To: Bart Van Assche <bart.vanassche@sandisk.com>, James Bottomley <jejb@linux.vnet.ibm.com>, "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>, Johannes Thumshirn <jthumshirn@suse.de>, "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>

Hey Bart,

> The solution I prefer is to modify the SCSI scanning code such that
> the scan_mutex is only held while performing the actual LUN scanning
> and while ensuring that no SCSI device has been created yet for a
> certain LUN number but not while the Linux device and its sysfs
> attributes are created. Since that approach would require extensive
> changes in the SCSI scanning code, another approach has been chosen,
> namely to make self-removal asynchronous. This patch avoids that
> self-removal triggers the following deadlock:

Is this a real deadlock? or just a lockdep complaint?

Wouldn't making scsi_remove_device() taking single depth
mutex_lock_nested suffice here?