"deadlock" between smc91x driver and link_watch

[Ian Campbell <icampbell@arcom.com>]

Hi,

I'm seeing a deadlock in linkwatch_event() when bringing down an
Ethernet interface using the smc91x driver (drivers/net/smc91x.c).

What I am seeing is that smc_close() is calling netif_carrier_off which
has the call chain:
	netif_carrier_off
	-> linkwatch_fire_event
	   -> schedule_work or schedule_delayed_work
The function that is scheduled is linkwatch_event().

smc_close() then goes on to call flush_scheduled_work() in order to
ensure that it's own pending workqueue stuff (smc_phy_configure()) is
completed before powering down the PHY.

What I am seeing is that linkwatch_event() is deadlocking trying take
rtnl_sem via rtnl_shlock(). The lock appears to already be held by a
call to rtnl_lock() from devinet_ioctl().

Any ideas? Perhaps smc_phy_configure calls could just check that the
interface is up before continuing, then there would be no need to flush
the queue to get rid of it.

Ian.

-- 
Ian Campbell, Senior Design Engineer
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