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 | |
| parent | d7a855bd6ab25d10d5e3b6aeb53d9c57fa17b808 (diff) | |
| download | talos-op-linux-f9e053dcfc02b0ad29daec8524fb1afe09774976.tar.gz talos-op-linux-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')
| -rw-r--r-- | include/linux/tty.h | 5 | ||||
| -rw-r--r-- | include/linux/tty_driver.h | 4 |
2 files changed, 8 insertions, 1 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 4cfd4a82fc31..fd4148d3a261 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -252,6 +252,7 @@ struct tty_struct { struct rw_semaphore termios_rwsem; struct mutex winsize_mutex; spinlock_t ctrl_lock; + spinlock_t flow_lock; /* Termios values are protected by the termios rwsem */ struct ktermios termios, termios_locked; struct termiox *termiox; /* May be NULL for unsupported */ @@ -261,7 +262,7 @@ struct tty_struct { unsigned long flags; int count; struct winsize winsize; /* winsize_mutex */ - int stopped; + int stopped; /* flow_lock */ int flow_stopped; int hw_stopped; int packet; @@ -400,7 +401,9 @@ extern int tty_paranoia_check(struct tty_struct *tty, struct inode *inode, extern char *tty_name(struct tty_struct *tty, char *buf); extern void tty_wait_until_sent(struct tty_struct *tty, long timeout); extern int tty_check_change(struct tty_struct *tty); +extern void __stop_tty(struct tty_struct *tty); extern void stop_tty(struct tty_struct *tty); +extern void __start_tty(struct tty_struct *tty); extern void start_tty(struct tty_struct *tty); extern int tty_register_driver(struct tty_driver *driver); extern int tty_unregister_driver(struct tty_driver *driver); 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. |
