| Message ID | e82ff9358d4ef90a7e9f624534d6d54fc193467f.1649310812.git.duoming@zju.edu.cn |
|---|---|
| State | New |
| Headers | show |
| Series | Fix deadlocks caused by del_timer_sync() | expand |
diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c index 5fe6cccfc1a..3a5f12ced0b 100644 --- a/drivers/tty/serial/sa1100.c +++ b/drivers/tty/serial/sa1100.c @@ -476,7 +476,9 @@ sa1100_set_termios(struct uart_port *port, struct ktermios *termios, UTSR1_TO_SM(UTSR1_ROR); } + spin_unlock_irqrestore(&sport->port.lock, flags); del_timer_sync(&sport->timer); + spin_lock_irqsave(&sport->port.lock, flags); /* * Update the per-port timeout.
There is a deadlock in sa1100_set_termios(), which is shown below: (Thread 1) | (Thread 2) | sa1100_enable_ms() sa1100_set_termios() | mod_timer() spin_lock_irqsave() //(1) | (wait a time) ... | sa1100_timeout() del_timer_sync() | spin_lock_irqsave() //(2) (wait timer to stop) | ... We hold sport->port.lock in position (1) of thread 1 and use del_timer_sync() to wait timer to stop, but timer handler also need sport->port.lock in position (2) of thread 2. As a result, sa1100_set_termios() will block forever. This patch extracts del_timer_sync() from the protection of spin_lock_irqsave(), which could let timer handler to obtain the needed lock. Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- drivers/tty/serial/sa1100.c | 2 ++ 1 file changed, 2 insertions(+)