> stack backtrace:
> [<f9099d31>] rtl8139_start_xmit+0xd9/0xff [8139too]
> [<c11ad5ea>] netpoll_send_skb+0x98/0xea
This seems to be a real deadlock...
So netpoll_send_skb takes the _xmit_lock, which is all nitty gritty
but then rtl8139_start_xmit comes around while that lock is taken, and
does
spin_unlock_irq(&tp->lock);
which.. enables interrupts and softirqs; this is quite bad because the
xmit lock is taken in softirq context for the watchdog like this:
[<c1200376>] _spin_lock+0x23/0x32
[<c11af282>] dev_watchdog+0x14/0xb1
[<c101dab2>] run_timer_softirq+0xf2/0x14a
[<c101a691>] __do_softirq+0x55/0xb0
[<c1004a8d>] do_softirq+0x58/0xbd
Which would deadlock now that the spin_unlock_irq() has enabled
irqs/softirqs while the _xmit_lock is still held.
The patch below turns this into a irqsave/irqrestore pair so that
interrupts don't get enabled unconditionally.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
bce305f4fe