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| 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 /Documentation/serial | |
| parent | serial: core: Flush ldisc after dropping port mutex in uart_close() (diff) | |
| download | linux-dev-7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96.tar.xz linux-dev-7c8ab967e3cd1513cd79fd5edc404fb43c7f3a96.zip | |
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>
Diffstat (limited to 'Documentation/serial')
| -rw-r--r-- | Documentation/serial/driver | 6 |
1 files changed, 4 insertions, 2 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 |