path: root/drivers/tty/pty.c
diff options
authorPeter Hurley <peter@hurleysoftware.com>2015-01-17 15:42:05 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-02-02 10:11:27 -0800
commit1d1d14da12e79a6c05fbe1a975401f0f56c93316 (patch)
tree6cbf288a73b5251633590e31da9b175be7311559 /drivers/tty/pty.c
parent3abf87cd3e70009ed70a7f28c2914888a7e27332 (diff)
pty: Fix buffer flush deadlock
The pty driver does not clear its write buffer when commanded. This is to avoid an apparent deadlock between parallel flushes from both pty ends; specifically when handling either BRK or INTR input. However, parallel flushes from this source is not possible since the pty master can never be set to BRKINT or ISIG. Parallel flushes from other sources are possible but these do not threaten deadlocks. Annotate the tty buffer mutex for lockdep to represent the nested tty_buffer locking which occurs when the pty slave is processing input (its buffer mutex held) and receives INTR or BRK and acquires the linked tty buffer mutex via tty_buffer_flush(). Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/pty.c')
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
index f882ac81b93a..0e273158edac 100644
--- a/drivers/tty/pty.c
+++ b/drivers/tty/pty.c
@@ -212,10 +212,16 @@ static int pty_signal(struct tty_struct *tty, int sig)
static void pty_flush_buffer(struct tty_struct *tty)
struct tty_struct *to = tty->link;
+ struct tty_ldisc *ld;
if (!to)
- /* tty_buffer_flush(to); FIXME */
+ ld = tty_ldisc_ref(to);
+ tty_buffer_flush(to, ld);
+ if (ld)
+ tty_ldisc_deref(ld);
if (to->packet) {
tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
@@ -425,6 +431,8 @@ static int pty_common_install(struct tty_driver *driver, struct tty_struct *tty,
tty->port = ports[1];
o_tty->port->itty = o_tty;
+ tty_buffer_set_lock_subclass(o_tty->port);

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