[NET]: Use local_irq_{save,restore}() in napi_complete().
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>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index a2f0032..fae6a7e 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -383,9 +383,11 @@
static inline void napi_complete(struct napi_struct *n)
{
- local_irq_disable();
+ unsigned long flags;
+
+ local_irq_save(flags);
__napi_complete(n);
- local_irq_enable();
+ local_irq_restore(flags);
}
/**