diff options
| author | Peter Hurley <peter@hurleysoftware.com> | 2015-01-17 15:42:04 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-02-02 10:11:27 -0800 |
| commit | 3abf87cd3e70009ed70a7f28c2914888a7e27332 (patch) | |
| tree | c1c57a8caab29cd953b7373c5a19d0a4f0494a14 /include/linux/tty.h | |
| parent | fb5ef9e7da39968fec6d6f37f20a23d23740c75e (diff) | |
| download | lwn-3abf87cd3e70009ed70a7f28c2914888a7e27332.tar.gz lwn-3abf87cd3e70009ed70a7f28c2914888a7e27332.zip | |
tty: Make lock subclasses available for other tty locks
Besides nested legacy_mutex locking which is required on pty pair
teardown, other nested pty operations require lock subclassing.
Move lock subclass definition to tty interface header, include/linux/tty.h,
and document its use.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include/linux/tty.h')
| -rw-r--r-- | include/linux/tty.h | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h index 7d66ae508e5c..849659908f23 100644 --- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -14,6 +14,23 @@ #include <linux/llist.h> +/* + * Lock subclasses for tty locks + * + * TTY_LOCK_NORMAL is for normal ttys and master ptys. + * TTY_LOCK_SLAVE is for slave ptys only. + * + * Lock subclasses are necessary for handling nested locking with pty pairs. + * tty locks which use nested locking: + * + * legacy_mutex - Nested tty locks are necessary for releasing pty pairs. + * The stable lock order is master pty first, then slave pty. + */ + +enum { + TTY_LOCK_NORMAL = 0, + TTY_LOCK_SLAVE, +}; /* * (Note: the *_driver.minor_start values 1, 64, 128, 192 are |