tty: Add a kref count

[linux-2.6-omap-h63xx.git] / drivers / char / tty_io.c

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 732316899ca48cc1bcaebaa842aad216e0d2ed54..310e0703e4a1281d172717ae5933e25946d9e253 100644 (file)
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -559,6 +559,7 @@ static void do_tty_hangup(struct work_struct *work)
        struct tty_ldisc *ld;
        int    closecount = 0, n;
        unsigned long flags;
+       int refs = 0;
 
        if (!tty)
                return;
@@ -625,8 +626,12 @@ static void do_tty_hangup(struct work_struct *work)
        if (tty->session) {
                do_each_pid_task(tty->session, PIDTYPE_SID, p) {
                        spin_lock_irq(&p->sighand->siglock);
-                       if (p->signal->tty == tty)
+                       if (p->signal->tty == tty) {
                                p->signal->tty = NULL;
+                               /* We defer the dereferences outside fo
+                                  the tasklist lock */
+                               refs++;
+                       }
                        if (!p->signal->leader) {
                                spin_unlock_irq(&p->sighand->siglock);
                                continue;
@@ -652,6 +657,10 @@ static void do_tty_hangup(struct work_struct *work)
        tty->ctrl_status = 0;
        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 
+       /* Account for the p->signal references we killed */
+       while (refs--)
+               tty_kref_put(tty);
+
        /*
         * If one of the devices matches a console pointer, we
         * cannot just call hangup() because that will cause
@@ -1424,6 +1433,7 @@ release_mem_out:
 
 /**
  *     release_one_tty         -       release tty structure memory
+ *     @kref: kref of tty we are obliterating
  *
  *     Releases memory associated with a tty structure, and clears out the
  *     driver table slots. This function is called when a device is no longer
@@ -1433,17 +1443,19 @@ release_mem_out:
  *             tty_mutex - sometimes only
  *             takes the file list lock internally when working on the list
  *     of ttys that the driver keeps.
- *             FIXME: should we require tty_mutex is held here ??
  */
-static void release_one_tty(struct tty_struct *tty, int idx)
+static void release_one_tty(struct kref *kref)
 {
+       struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
        int devpts = tty->driver->flags & TTY_DRIVER_DEVPTS_MEM;
        struct ktermios *tp;
+       int idx = tty->index;
 
        if (!devpts)
                tty->driver->ttys[idx] = NULL;
 
        if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
+               /* FIXME: Locking on ->termios array */
                tp = tty->termios;
                if (!devpts)
                        tty->driver->termios[idx] = NULL;
@@ -1457,6 +1469,7 @@ static void release_one_tty(struct tty_struct *tty, int idx)
 
 
        tty->magic = 0;
+       /* FIXME: locking on tty->driver->refcount */
        tty->driver->refcount--;
 
        file_list_lock();
@@ -1466,6 +1479,21 @@ static void release_one_tty(struct tty_struct *tty, int idx)
        free_tty_struct(tty);
 }
 
+/**
+ *     tty_kref_put            -       release a tty kref
+ *     @tty: tty device
+ *
+ *     Release a reference to a tty device and if need be let the kref
+ *     layer destruct the object for us
+ */
+
+void tty_kref_put(struct tty_struct *tty)
+{
+       if (tty)
+               kref_put(&tty->kref, release_one_tty);
+}
+EXPORT_SYMBOL(tty_kref_put);
+
 /**
  *     release_tty             -       release tty structure memory
  *
@@ -1477,14 +1505,20 @@ static void release_one_tty(struct tty_struct *tty, int idx)
  *             takes the file list lock internally when working on the list
  *     of ttys that the driver keeps.
  *             FIXME: should we require tty_mutex is held here ??
+ *
+ *     FIXME: We want to defer the module put of the driver to the
+ *     destructor.
  */
 static void release_tty(struct tty_struct *tty, int idx)
 {
        struct tty_driver *driver = tty->driver;
 
+       /* This should always be true but check for the moment */
+       WARN_ON(tty->index != idx);
+
        if (tty->link)
-               release_one_tty(tty->link, idx);
-       release_one_tty(tty, idx);
+               tty_kref_put(tty->link);
+       tty_kref_put(tty);
        module_put(driver->owner);
 }
 
@@ -2798,6 +2832,7 @@ EXPORT_SYMBOL(do_SAK);
 static void initialize_tty_struct(struct tty_struct *tty)
 {
        memset(tty, 0, sizeof(struct tty_struct));
+       kref_init(&tty->kref);
        tty->magic = TTY_MAGIC;
        tty_ldisc_init(tty);
        tty->session = NULL;
@@ -3053,9 +3088,12 @@ EXPORT_SYMBOL(tty_devnum);
 
 void proc_clear_tty(struct task_struct *p)
 {
+       struct tty_struct *tty;
        spin_lock_irq(&p->sighand->siglock);
+       tty = p->signal->tty;
        p->signal->tty = NULL;
        spin_unlock_irq(&p->sighand->siglock);
+       tty_kref_put(tty);
 }
 
 /* Called under the sighand lock */
@@ -3071,9 +3109,13 @@ static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
                tty->pgrp = get_pid(task_pgrp(tsk));
                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
                tty->session = get_pid(task_session(tsk));
+               if (tsk->signal->tty) {
+                       printk(KERN_DEBUG "tty not NULL!!\n");
+                       tty_kref_put(tsk->signal->tty);
+               }
        }
        put_pid(tsk->signal->tty_old_pgrp);
-       tsk->signal->tty = tty;
+       tsk->signal->tty = tty_kref_get(tty);
        tsk->signal->tty_old_pgrp = NULL;
 }