GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-06-19 13:11:14 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

tty: Serialize tty flow control changes with flow_lock

Browse source 
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>
This commit is contained in:
Peter Hurley 2014-09-10 15:06:31 -04:00 • committed by Greg Kroah-Hartman
parent d7a855bd6a
commit f9e053dcfc
3 changed files with 36 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/linux/tty_driver.h
View file

@ -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.