Based upon a lockdep report.
Since ->poll() can be invoked from netpoll with interrupts
disabled, we must not unconditionally enable interrupts
in napi_complete().
Instead we must use local_irq_{save,restore}().
Noticed by Peter Zijlstra:
<irqs disabled>
netpoll_poll()
poll_napi()
spin_trylock(&napi->poll_lock)
poll_one_napi()
napi->poll() := sky2_poll()
napi_complete()
local_irq_disable()
local_irq_enable() <--- *BUG*
<irq>
irq_exit()
do_softirq()
net_rx_action()
spin_lock(&napi->poll_lock) <--- Deadlock!
Because we still hold the lock....
Signed-off-by: David S. Miller <davem@davemloft.net>
50fd4407b8