As &hc->lock is acquired by both timer _hfcpci_softirq() and hardirq
hfcpci_int(), the timer should disable irq before lock acquisition
otherwise deadlock could happen if the timmer is preemtped by the hadr irq.
Possible deadlock scenario:
hfcpci_softirq() (timer)
-> _hfcpci_softirq()
-> spin_lock(&hc->lock);
<irq interruption>
-> hfcpci_int()
-> spin_lock(&hc->lock); (deadlock here)
This flaw was found by an experimental static analysis tool I am developing
for irq-related deadlock.
The tentative patch fixes the potential deadlock by spin_lock_irq()
in timer.
Fixes: b36b654a7e ("mISDN: Create /sys/class/mISDN")
Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Link: https://lore.kernel.org/r/20230727085619.7419-1-dg573847474@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
56c6be35fc