Re: [PATCH] sc16is7xx: drop bogus use of IRQF_ONESHOT

From: Sean NyekjÃr
Date: Tue Mar 08 2016 - 07:43:45 EST

On 2016-02-18 18:26, Josh Cartwright wrote:
The use of IRQF_ONESHOT when registering an interrupt handler with
request_irq() is non-sensical.

Not only that, it also prevents the handler from being threaded when it
otherwise should be w/ IRQ_FORCED_THREADING is enabled. This causes the
following deadlock observed by Sean Nyekjaer on -rt:

Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
rt_spin_lock_slowlock from (queue_kthread_work+0x18/0x74)
queue_kthread_work) from (sc16is7xx_irq+0x10/0x18 [sc16is7xx])
sc16is7xx_irq [sc16is7xx]) from (handle_irq_event_percpu+0x70/0x158)
handle_irq_event_percpu) from (handle_irq_event+0x68/0xa8)
handle_irq_event) from (handle_level_irq+0x10c/0x184)
handle_level_irq) from (generic_handle_irq+0x2c/0x3c)
generic_handle_irq) from (mxc_gpio_irq_handler+0x3c/0x108)
mxc_gpio_irq_handler) from (mx3_gpio_irq_handler+0x80/0xcc)
mx3_gpio_irq_handler) from (generic_handle_irq+0x2c/0x3c)
generic_handle_irq) from (__handle_domain_irq+0x7c/0xe8)
__handle_domain_irq) from (gic_handle_irq+0x24/0x5c)
gic_handle_irq) from (__irq_svc+0x40/0x88)
(__irq_svc) from (rt_spin_unlock+0x1c/0x68)
(rt_spin_unlock) from (kthread_worker_fn+0x104/0x17c)
(kthread_worker_fn) from (kthread+0xd0/0xe8)
(kthread) from (ret_from_fork+0x14/0x2c)

Reported-by: Sean Nyekjaer <sean.nyekjaer@xxxxxxxxx>
Fixes: 9e6f4ca3e567 ("sc16is7xx: use kthread_worker for tx_work and irq")
Cc: stable@xxxxxxxxxxxxxxx # v4.1+
Signed-off-by: Josh Cartwright <joshc@xxxxxx>
drivers/tty/serial/sc16is7xx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index e78fa99..1bb5c0e 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -1257,7 +1257,7 @@ static int sc16is7xx_probe(struct device *dev,
/* Setup interrupt */
ret = devm_request_irq(dev, irq, sc16is7xx_irq,
- IRQF_ONESHOT | flags, dev_name(dev), s);
+ flags, dev_name(dev), s);
if (!ret)
return 0;
Is PATCH this dropped?
It clearly fixes the irq when running with RT patches :-)