diff options
| author |   Peter Hurley <peter@hurleysoftware.com> | 2014-09-10 15:06:31 -0400 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-09-23 21:19:35 -0700 |
| commit | f9e053dcfc02b0ad29daec8524fb1afe09774976 (patch) | |
| tree | 2d930c2d89b011b40c03eeb13ee6f431cb602d3f /include/linux/tty_driver.h | |
| parent | tty: Convert tty_struct bitfield to ints (diff) | |
| download | linux-dev-f9e053dcfc02b0ad29daec8524fb1afe09774976.tar.xz linux-dev-f9e053dcfc02b0ad29daec8524fb1afe09774976.zip | |
tty: Serialize tty flow control changes with flow_lock
Without serialization, the flow control state can become inverted
wrt. the actual hardware state. For example,
CPU 0 | CPU 1
stop_tty() |
lock ctrl_lock |
tty->stopped = 1 |
unlock ctrl_lock |
| start_tty()
| lock ctrl_lock
| tty->stopped = 0
| unlock ctrl_lock
| driver->start()
driver->stop() |
In this case, the flow control state now indicates the tty has
been started, but the actual hardware state has actually been stopped.
Introduce tty->flow_lock spinlock to serialize tty flow control changes.
Split out unlocked __start_tty()/__stop_tty() flavors for use by
ioctl(TCXONC) in follow-on patch.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/tty_driver.h')
| -rw-r--r-- | include/linux/tty_driver.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h index e48c608a8fa8..92e337c18839 100644 --- a/include/linux/tty_driver.h +++ b/include/linux/tty_driver.h @@ -152,6 +152,8 @@ * This routine notifies the tty driver that it should stop * outputting characters to the tty device. * + * Called with ->flow_lock held. Serialized with start() method. + * * Optional: * * Note: Call stop_tty not this method. @@ -161,6 +163,8 @@ * This routine notifies the tty driver that it resume sending * characters to the tty device. * + * Called with ->flow_lock held. Serialized with stop() method. + * * Optional: * * Note: Call start_tty not this method. |