linux-kernel - RE: System reboot hangs due to race against devices_kset->list triggered by SCSI FC workqueue

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Date:	Fri, 5 Mar 2010 09:31:02 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Hugh Daschbach <hdasch@...adcom.com>
cc:	Greg KH <gregkh@...e.de>, Kay Sievers <kay.sievers@...y.org>,
	Jan Blunck <jblunck@...e.de>,
	David Vrabel <david.vrabel@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	james Bottomley <James.Bottomley@...e.de>,
	James Smart <james.smart@...lex.com>
Subject: RE: System reboot hangs due to race against devices_kset->list
 triggered by SCSI FC workqueue

On Thu, 4 Mar 2010, Hugh Daschbach wrote:

> I have added get_device()/put_device() to ensure there's the device
> hasn't fully disappeared before calling list_del_init().  Is this
> needed?

Yes, it is.  In fact, it's necessary to insure the device doesn't
disappear before you call the shutdown routines!

>  If so, there's "might_sleep()" commented out in put_device().
> Do I need to release the lock before calling put_device()?

A better approach might be to do the list_del_init() while still 
holding the initial spinlock, before you call the shutdown methods.  
Then do the put_device() before reacquiring the spinlock at the end of 
the loop.

Alan Stern

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