From: Uwe Kleine-König <u.kleine-koe...@pengutronix.de> Date: Sun, 22 Jul 2018 21:00:35 +0200
> On Sat, Jul 21, 2018 at 10:44:09PM -0700, David Miller wrote: >> From: Uwe Kleine-König <u.kleine-koe...@pengutronix.de> >> Date: Fri, 20 Jul 2018 11:53:15 +0200 >> >> > free_irq() waits until all handlers for this IRQ have completed. As the >> > relevant handler (mv88e6xxx_g1_irq_thread_fn()) takes the chip's reg_lock >> > it might never return if the thread calling free_irq() holds this lock. >> > >> > For the same reason kthread_cancel_delayed_work_sync() in the polling case >> > must not hold this lock. >> > >> > Also first free the irq (or stop the worker respectively) such that >> > mv88e6xxx_g1_irq_thread_work() isn't called any more before the irq >> > mappings are dropped in mv88e6xxx_g1_irq_free_common() to prevent the >> > worker thread to call handle_nested_irq(0) which results in a NULL-pointer >> > exception. >> > >> > Signed-off-by: Uwe Kleine-König <u.kleine-koe...@pengutronix.de> >> >> Looks good. >> >> Note than the IRQ domain unmapping will do a synchronize_irq() which >> should cause the same deadlock as free_irq() will with the reg_lock >> held. > > Do you think that there is still a problem? When free_irq() for the > external visible irq returns the muxed irqs should be all gone, too, so > this should not trigger, should it? It shouldn't be a problem after your changes. I'm just saying that I'm surprised that, in the original code, you see the deadlock in free_irq(), since the synchronize_irq() done by the IRQ domain code should have happened first.
