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authorSerge Semin <fancer.lancer@gmail.com>2019-05-08 13:44:41 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-06-18 09:52:26 +0200
commit13b18d35909707571af9539f7731389fbf0feb31 (patch)
tree23584fe83457705e3155f5890179ead204cea31e /drivers/tty
parent42912081481c6303d880f315223f725ee813c8f1 (diff)
tty: serial_core: Set port active bit in uart_port_activate
A bug was introduced by commit b3b576461864 ("tty: serial_core: convert uart_open to use tty_port_open"). It caused a constant warning printed into the system log regarding the tty and port counter mismatch: [ 21.644197] ttyS ttySx: tty_port_close_start: tty->count = 1 port count = 2 in case if session hangup was detected so the warning is printed starting from the second open-close iteration. Particularly the problem was discovered in situation when there is a serial tty device without hardware back-end being setup. It is considered by the tty-serial subsystems as a hardware problem with session hang up. In this case uart_startup() will return a positive value with TTY_IO_ERROR flag set in corresponding tty_struct instance. The same value will get passed to be returned from the activate() callback and then being returned from tty_port_open(). But since in this case tty_port_block_til_ready() isn't called the TTY_PORT_ACTIVE flag isn't set (while the method had been called before tty_port_open conversion was introduced and the rest of the subsystem code expected the bit being set in this case), which prevents the uart_hangup() method to perform any cleanups including the tty port counter setting to zero. So the next attempt to open/close the tty device will discover the counters mismatch. In order to fix the problem we need to manually set the TTY_PORT_ACTIVE flag in case if uart_startup() returned a positive value. In this case the hang up procedure will perform a full set of cleanup actions including the port ref-counter resetting. Fixes: b3b576461864 "tty: serial_core: convert uart_open to use tty_port_open" Signed-off-by: Serge Semin <fancer.lancer@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/serial_core.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 83f4dd0bfd74..4223cb496764 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1777,6 +1777,7 @@ static int uart_port_activate(struct tty_port *port, struct tty_struct *tty)
{
struct uart_state *state = container_of(port, struct uart_state, port);
struct uart_port *uport;
+ int ret;
uport = uart_port_check(state);
if (!uport || uport->flags & UPF_DEAD)
@@ -1787,7 +1788,11 @@ static int uart_port_activate(struct tty_port *port, struct tty_struct *tty)
/*
* Start up the serial port.
*/
- return uart_startup(tty, state, 0);
+ ret = uart_startup(tty, state, 0);
+ if (ret > 0)
+ tty_port_set_active(port, 1);
+
+ return ret;
}
static const char *uart_type(struct uart_port *port)