commit 7a58b8d602 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: 3a316ec4c9 ("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>
ead83b0db8