[ Upstream commit eb5adc70754d26a260f8b42d39db42da0d0af500 ]
There is a deadlock in rs_close(), which is shown
below:
(Thread 1) | (Thread 2)
| rs_open()
rs_close() | mod_timer()
spin_lock_bh() //(1) | (wait a time)
... | rs_poll()
del_timer_sync() | spin_lock() //(2)
(wait timer to stop) | ...
We hold timer_lock in position (1) of thread 1 and
use del_timer_sync() to wait timer to stop, but timer handler
also need timer_lock in position (2) of thread 2.
As a result, rs_close() will block forever.
This patch deletes the redundant timer_lock in order to
prevent the deadlock. Because there is no race condition
between rs_close, rs_open and rs_poll.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Message-Id: <20220407154430.22387-1-duoming@zju.edu.cn>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
50f79a2abb