netdev - RE: [PATCH net-next] r8152: use mutex for hw settings

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Message-ID: <0835B3720019904CB8F7AA43166CEEB2EC397B@RTITMBSTEMP01.realtek.com.tw>
Date:	Thu, 9 Oct 2014 07:59:35 +0000
From:	Hayes Wang <hayeswang@...ltek.com>
To:	David Miller <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	nic_swsd <nic_swsd@...ltek.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>
Subject: RE: [PATCH net-next] r8152: use mutex for hw settings

 David Miller [mailto:davem@...emloft.net] 
> Sent: Thursday, October 09, 2014 3:45 AM
[..]
> I think a much simpler fix is to take rtnl_lock() in the workqueue
> function and suspend/resume ops.
> 
> Every other place you are adding the mutex already holds the RTNL
> mutex.

If I use the rtnl_lock(), I get a dead lock when enabling autosuspend.

Case 1:
   autosuspend before calling open.
   rtnl_lock()
   call open
   try to autoresume and rtl8152_resume is called.
   dead lock occurs.

Case 2:
   autosuspend occurs.
   rtnl_lock()
   call close
   try to autoresume and rtl8152_resume is called.
   dead lock occurs.
 
Best Regards,
Hayes
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