From: Duoming Zhou duoming@zju.edu.cn
commit 7a58b8d6021426b796eebfae80983374d9a80a75 upstream.
There is a deadlock in ci_otg_del_timer(), the process is shown below:
(thread 1) | (thread 2) ci_otg_del_timer() | ci_otg_hrtimer_func() ... | spin_lock_irqsave() //(1) | ... ... | hrtimer_cancel() | spin_lock_irqsave() //(2) (block forever)
We hold ci->lock in position (1) and use hrtimer_cancel() to wait ci_otg_hrtimer_func() to stop, but ci_otg_hrtimer_func() also need ci->lock in position (2). As a result, the hrtimer_cancel() in ci_otg_del_timer() will be blocked forever.
This patch extracts hrtimer_cancel() from the protection of spin_lock_irqsave() in order that the ci_otg_hrtimer_func() could obtain the ci->lock.
What`s more, there will be no race happen. Because the "next_timer" is always under the protection of spin_lock_irqsave() and we only check whether "next_timer" equals to NUM_OTG_FSM_TIMERS in the following code.
Fixes: 3a316ec4c91c ("usb: chipidea: use hrtimer for otg fsm timers") Cc: stable stable@kernel.org Signed-off-by: Duoming Zhou duoming@zju.edu.cn Link: https://lore.kernel.org/r/20220918033312.94348-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/chipidea/otg_fsm.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/usb/chipidea/otg_fsm.c +++ b/drivers/usb/chipidea/otg_fsm.c @@ -256,8 +256,10 @@ static void ci_otg_del_timer(struct ci_h ci->enabled_otg_timer_bits &= ~(1 << t); if (ci->next_otg_timer == t) { if (ci->enabled_otg_timer_bits == 0) { + spin_unlock_irqrestore(&ci->lock, flags); /* No enabled timers after delete it */ hrtimer_cancel(&ci->otg_fsm_hrtimer); + spin_lock_irqsave(&ci->lock, flags); ci->next_otg_timer = NUM_OTG_FSM_TIMERS; } else { /* Find the next timer */