diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2014-10-16 16:54:20 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-11-05 18:53:54 -0800 |
| commit | 7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96 (patch) | |
| tree | 2fadec4ea6f6d183b2b6e5b81453a57b8670e390 | |
| parent | 2e758910832dce99761a29688b33fd77dcbf6f6c (diff) | |
serial: Fix locking for uart driver set_termios() method
The low-level uart driver may modify termios settings to override
settings that are not compatible with the uart, such as CRTSCTS.
Thus, callers of the low-level uart driver's set_termios() method must
hold termios_rwsem write lock to prevent concurrent access to termios,
in case such override occurs.
The termios_rwsem lock requirement does not extend to console setup
(ie., uart_set_options), as console setup cannot race with tty
operations. Nor does this lock requirement extend to functions which
cannot be concurrent with tty ioctls (ie., uart_port_startup() and
uart_resume_port()).
Further, always claim the port mutex to protect hardware
re-reprogramming in the set_termios() uart driver method. Note this
is unnecessary for console initialization in uart_set_options()
which cannot be concurrent with other uart operations.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | Documentation/serial/driver | 6 | ||||
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 8 |
2 files changed, 11 insertions, 3 deletions
diff --git a/Documentation/serial/driver b/Documentation/serial/driver index ba64e4b892e9..c415b0ef4493 100644 --- a/Documentation/serial/driver +++ b/Documentation/serial/driver @@ -59,7 +59,9 @@ The core driver uses the info->tmpbuf_sem lock to prevent multi-threaded access to the info->tmpbuf bouncebuffer used for port writes. The port_sem semaphore is used to protect against ports being added/ -removed or reconfigured at inappropriate times. +removed or reconfigured at inappropriate times. Since v2.6.27, this +semaphore has been the 'mutex' member of the tty_port struct, and +commonly referred to as the port mutex (or port->mutex). uart_ops @@ -248,7 +250,7 @@ hardware. Other flags may be used (eg, xon/xoff characters) if your hardware supports hardware "soft" flow control. - Locking: none. + Locking: caller holds port->mutex Interrupts: caller dependent. This call must not sleep diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 9d142972ee2d..e31d56159aee 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -436,7 +436,7 @@ uart_get_divisor(struct uart_port *port, unsigned int baud) EXPORT_SYMBOL(uart_get_divisor); -/* FIXME: Consistent locking policy */ +/* Caller holds port mutex */ static void uart_change_speed(struct tty_struct *tty, struct uart_state *state, struct ktermios *old_termios) { @@ -1173,11 +1173,15 @@ uart_ioctl(struct tty_struct *tty, unsigned int cmd, break; case TIOCSSERIAL: + down_write(&tty->termios_rwsem); ret = uart_set_info_user(tty, state, uarg); + up_write(&tty->termios_rwsem); break; case TIOCSERCONFIG: + down_write(&tty->termios_rwsem); ret = uart_do_autoconfig(tty, state); + up_write(&tty->termios_rwsem); break; case TIOCSERGWILD: /* obsolete */ @@ -1278,7 +1282,9 @@ static void uart_set_termios(struct tty_struct *tty, return; } + mutex_lock(&state->port.mutex); uart_change_speed(tty, state, old_termios); + mutex_unlock(&state->port.mutex); /* reload cflag from termios; port driver may have overriden flags */ cflag = tty->termios.c_cflag; |