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 moves del_timer_sync() before spin_lock_irqsave()
in order to prevent the deadlock.
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
Changes in V2:
- Move del_timer_sync() before spin_lock_irqsave().
drivers/tty/serial/sa1100.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c
index 5fe6cccfc1a..041e6bca0dc 100644
--- a/drivers/tty/serial/sa1100.c
+++ b/drivers/tty/serial/sa1100.c
@@ -445,7 +445,7 @@ sa1100_set_termios(struct uart_port *port, struct ktermios *termios,
*/
baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
quot = uart_get_divisor(port, baud);
-
+ del_timer_sync(&sport->timer);
spin_lock_irqsave(&sport->port.lock, flags);
sport->port.read_status_mask &= UTSR0_TO_SM(UTSR0_TFS);
@@ -476,8 +476,6 @@ sa1100_set_termios(struct uart_port *port, struct ktermios *termios,
UTSR1_TO_SM(UTSR1_ROR);
}
- del_timer_sync(&sport->timer);
-
/*
* Update the per-port timeout.
*/
--
2.17.1
