usb: chipidea: fix deadlock in ci_otg_del_timer

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 <[email protected]>
Signed-off-by: Duoming Zhou <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions