Re: [PATCH V2 11/11] arch: xtensa: platforms: Fix deadlock in rs_close()
From: Max Filippov
Date: Thu Apr 07 2022 - 18:09:18 EST
On Thu, Apr 7, 2022 at 8:44 AM Duoming Zhou <duoming@xxxxxxxxxx> wrote:
> There is a deadlock in rs_close(), which is shown
> (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@xxxxxxxxxx>
> Changes in V2:
> - Remove the timer_lock.
> arch/xtensa/platforms/iss/console.c | 8 --------
> 1 file changed, 8 deletions(-)
Thanks. Applied to my xtensa tree.