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authorDuoming Zhou <duoming@zju.edu.cn>2022-04-17 19:16:26 +0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-06-14 16:52:39 +0200
commit0976808d0d171ec837d4bd3e9f4ad4a00ab703b8 (patch)
tree858406b0f6384b946ae1250c5bbd9ba0fce3f7cb
parent804de302ada3544699c5f48c5314b249af76faa3 (diff)
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drivers: tty: serial: Fix deadlock in sa1100_set_termios()
[ Upstream commit 62b2caef400c1738b6d22f636c628d9f85cd4c4c ] 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@zju.edu.cn> Link: https://lore.kernel.org/r/20220417111626.7802-1-duoming@zju.edu.cn Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r--drivers/tty/serial/sa1100.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/tty/serial/sa1100.c b/drivers/tty/serial/sa1100.c
index fd3d1329d48c..68eb1c9faa29 100644
--- a/drivers/tty/serial/sa1100.c
+++ b/drivers/tty/serial/sa1100.c
@@ -452,6 +452,8 @@ 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);
@@ -482,8 +484,6 @@ 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.
*/