These changes are the raw update to linux-4.4.6-rt14. Kernel sources

[kvmfornfv.git] / kernel / drivers / tty / pty.c

diff --git a/kernel/drivers/tty/pty.c b/kernel/drivers/tty/pty.c
index 4d5e840..78e9836 100644 (file)
--- a/kernel/drivers/tty/pty.c
+++ b/kernel/drivers/tty/pty.c
@@ -7,7 +7,6 @@
  */
 
 #include <linux/module.h>
-
 #include <linux/errno.h>
 #include <linux/interrupt.h>
 #include <linux/tty.h>
@@ -26,6 +25,12 @@
 #include <linux/mutex.h>
 #include <linux/poll.h>
 
+#undef TTY_DEBUG_HANGUP
+#ifdef TTY_DEBUG_HANGUP
+# define tty_debug_hangup(tty, f, args...)     tty_debug(tty, f, ##args)
+#else
+# define tty_debug_hangup(tty, f, args...)     do {} while (0)
+#endif
 
 #ifdef CONFIG_UNIX98_PTYS
 static struct tty_driver *ptm_driver;
@@ -495,6 +500,10 @@ static int pty_bsd_ioctl(struct tty_struct *tty,
 }
 
 static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
+/*
+ * not really modular, but the easiest way to keep compat with existing
+ * bootargs behaviour is to continue using module_param here.
+ */
 module_param(legacy_count, int, 0);
 
 /*
@@ -672,7 +681,14 @@ static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
 /* this is called once with whichever end is closed last */
 static void pty_unix98_shutdown(struct tty_struct *tty)
 {
-       devpts_kill_index(tty->driver_data, tty->index);
+       struct inode *ptmx_inode;
+
+       if (tty->driver->subtype == PTY_TYPE_MASTER)
+               ptmx_inode = tty->driver_data;
+       else
+               ptmx_inode = tty->link->driver_data;
+       devpts_kill_index(ptmx_inode, tty->index);
+       devpts_del_ref(ptmx_inode);
 }
 
 static const struct tty_operations ptm_unix98_ops = {
@@ -764,6 +780,18 @@ static int ptmx_open(struct inode *inode, struct file *filp)
        set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
        tty->driver_data = inode;
 
+       /*
+        * In the case where all references to ptmx inode are dropped and we
+        * still have /dev/tty opened pointing to the master/slave pair (ptmx
+        * is closed/released before /dev/tty), we must make sure that the inode
+        * is still valid when we call the final pty_unix98_shutdown, thus we
+        * hold an additional reference to the ptmx inode. For the same /dev/tty
+        * last close case, we also need to make sure the super_block isn't
+        * destroyed (devpts instance unmounted), before /dev/tty is closed and
+        * on its release devpts_kill_index is called.
+        */
+       devpts_add_ref(inode);
+
        tty_add_file(tty, filp);
 
        slave_inode = devpts_pty_new(inode,
@@ -779,6 +807,8 @@ static int ptmx_open(struct inode *inode, struct file *filp)
        if (retval)
                goto err_release;
 
+       tty_debug_hangup(tty, "(tty count=%d)\n", tty->count);
+
        tty_unlock(tty);
        return 0;
 err_release:
@@ -869,4 +899,4 @@ static int __init pty_init(void)
        unix98_pty_init();
        return 0;
 }
-module_init(pty_init);
+device_initcall(pty_init);