tty: Convert termios_mutex to termios_rwsem

termios is commonly accessed unsafely (especially by N_TTY)
because the existing mutex forces exclusive access.
Convert existing usage.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 8323ee4f95b9..d3042076d163 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -10,6 +10,7 @@
 #include <linux/mutex.h>
 #include <linux/tty_flags.h>
 #include <uapi/linux/tty.h>
+#include <linux/rwsem.h>
 
 
 
@@ -243,9 +244,9 @@ struct tty_struct {
 
         struct mutex atomic_write_lock;
         struct mutex legacy_mutex;
-        struct mutex termios_mutex;
+        struct rw_semaphore termios_rwsem;
         spinlock_t ctrl_lock;
-        /* Termios values are protected by the termios mutex */
+        /* Termios values are protected by the termios rwsem */
         struct ktermios termios, termios_locked;
         struct termiox *termiox;        /* May be NULL for unsupported */
         char name[64];
@@ -253,7 +254,7 @@ struct tty_struct {
         struct pid *session;
         unsigned long flags;
         int count;
-        struct winsize winsize;         /* termios mutex */
+        struct winsize winsize;         /* termios rwsem */
         unsigned char stopped:1, hw_stopped:1, flow_stopped:1, packet:1;
         unsigned char ctrl_status;      /* ctrl_lock */
         unsigned int receive_room;      /* Bytes free for queue */