[PATCH -next 21/27] pty: Don't drop pty master tty lock to hangup slave

Peter Hurley
2014-10-16T21:02:24Z

Introduce tty_vhangup_slave(), which takes tty_lock_slave() instead
of tty_lock(), and thus is callable while holding the pty master
tty lock.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
---
drivers/tty/pty.c | 4 +---
drivers/tty/tty_io.c | 20 ++++++++++++++++++++
include/linux/tty.h | 1 +
3 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index bdb8fd1..09fb513 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -66,9 +66,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
mutex_unlock(&devpts_mutex);
}
#endif
- tty_unlock(tty);
- tty_vhangup(tty->link);
- tty_lock(tty);
+ tty_vhangup_slave(tty->link);
}
}

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 48c1def..25e85b0 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -809,6 +809,26 @@ void tty_vhangup(struct tty_struct *tty)

EXPORT_SYMBOL(tty_vhangup);

+/**
+ * tty_vhangup_slave - process vhangup for pty slave
+ * @tty: pty slave to hangup
+ *
+ * Identical to tty_vhangup(), except can specifically be used
+ * to synchronously hangup a pty slave while holding pty master
+ * tty lock.
+ */
+
+static void __tty_vhangup_slave(struct tty_struct *tty, int exit_session)
+{
+ tty_lock_slave(tty);
+ __tty_hangup_common(tty, 0);
+ tty_unlock_slave(tty);
+}
+
+void tty_vhangup_slave(struct tty_struct *tty)
+{
+ __tty_hangup(tty, 0, __tty_vhangup_slave);
+}

/**
* tty_vhangup_self - process vhangup for own ctty
diff --git a/include/linux/tty.h b/include/linux/tty.h
index d470a86..8a90253 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -435,6 +435,7 @@ extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
+extern void tty_vhangup_slave(struct tty_struct *tty);
extern int tty_hung_up_p(struct file *filp);
extern void do_SAK(struct tty_struct *tty);
extern void __do_SAK(struct tty_struct *tty);
--
2.1.1