RE: [PATCH for-next] iw_cxgb4: Fix possible circular dependency locking warning

["Steve Wise" <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

> 
> Locking sequence of iw_cxgb4 and RoCE drivers in ib_register_device() is
> slightly different and this leads to possible circular dependency locking
> warning when both the devices are brought up.
> 
> Here is the locking sequence upto ib_register_device():
> iw_cxgb4: rtnl_mutex(net stack) --> uld_mutex --> device_mutex
> RoCE drivers: device_mutex --> rtnl_mutex
> 
> Here is the possibility of cross locking:
> 
> 	CPU #0 (iw_cxgb4) 		     CPU #1 (RoCE drivers)
> 
> -> on interface up cxgb4_up()
> executed with rtnl_mutex held
> -> hold uld_mutex and try
> registering ib device
> 					-> In ib_register_device() hold
> 					   device_mutex
> -> hold device mutex in
> ib_register_device
> 					-> try acquiring rtnl_mutex in
> 					   ib_enum_roce_netdev()
> 
> Current patch schedules the ib_register_device() functionality of
> iw_cxgb4 to a workqueue to prevent the possible cross-locking.
> Also rename the labels in c4iw_reister_device().
> 
> Signed-off-by: Potnuri Bharat Teja <bharat-ut6Up61K2wZBDgjK7y7TUQ@public.gmane.org>

Reviewed-by: Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>


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