tty: BKL pushdown

[linux-2.6-block.git] / drivers / char / n_tty.c

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 0c09409fa45d4dc5f13a212c0211bab5fb307ae7..001d9d875387003a4326680ae497f1658d10ea3b 100644 (file)
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -183,22 +183,24 @@ static void reset_buffer_flags(struct tty_struct *tty)
  *     at hangup) or when the N_TTY line discipline internally has to
  *     clean the pending queue (for example some signals).
  *
- *     FIXME: tty->ctrl_status is not spinlocked and relies on
- *     lock_kernel() still.
+ *     Locking: ctrl_lock
  */
 
 static void n_tty_flush_buffer(struct tty_struct *tty)
 {
+       unsigned long flags;
        /* clear everything and unthrottle the driver */
        reset_buffer_flags(tty);
 
        if (!tty->link)
                return;
 
+       spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (tty->link->packet) {
                tty->ctrl_status |= TIOCPKT_FLUSHREAD;
                wake_up_interruptible(&tty->link->read_wait);
        }
+       spin_unlock_irqrestore(&tty->ctrl_lock, flags);
 }
 
 /**
@@ -264,7 +266,7 @@ static inline int is_continuation(unsigned char c, struct tty_struct *tty)
  *     relevant in the world today. If you ever need them, add them here.
  *
  *     Called from both the receive and transmit sides and can be called
- *     re-entrantly. Relies on lock_kernel() still.
+ *     re-entrantly. Relies on lock_kernel() for tty->column state.
  */
 
 static int opost(unsigned char c, struct tty_struct *tty)
@@ -275,6 +277,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
        if (!space)
                return -1;
 
+       lock_kernel();
        if (O_OPOST(tty)) {
                switch (c) {
                case '\n':
@@ -323,6 +326,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
                }
        }
        tty->driver->put_char(tty, c);
+       unlock_kernel();
        return 0;
 }
 
@@ -337,7 +341,8 @@ static int opost(unsigned char c, struct tty_struct *tty)
  *     the simple cases normally found and helps to generate blocks of
  *     symbols for the console driver and thus improve performance.
  *
- *     Called from write_chan under the tty layer write lock.
+ *     Called from write_chan under the tty layer write lock. Relies
+ *     on lock_kernel for the tty->column state.
  */
 
 static ssize_t opost_block(struct tty_struct *tty,
@@ -353,6 +358,7 @@ static ssize_t opost_block(struct tty_struct *tty,
        if (nr > space)
                nr = space;
 
+       lock_kernel();
        for (i = 0, cp = buf; i < nr; i++, cp++) {
                switch (*cp) {
                case '\n':
@@ -387,6 +393,7 @@ break_out:
        if (tty->driver->flush_chars)
                tty->driver->flush_chars(tty);
        i = tty->driver->write(tty, buf, i);
+       unlock_kernel();
        return i;
 }
 
@@ -1194,6 +1201,11 @@ extern ssize_t redirected_tty_write(struct file *, const char __user *,
  *     Perform job control management checks on this file/tty descriptor
  *     and if appropriate send any needed signals and return a negative
  *     error code if action should be taken.
+ *
+ *     FIXME:
+ *     Locking: None - redirected write test is safe, testing
+ *     current->signal should possibly lock current->sighand
+ *     pgrp locking ?
  */
 
 static int job_control(struct tty_struct *tty, struct file *file)
@@ -1246,6 +1258,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
        ssize_t size;
        long timeout;
        unsigned long flags;
+       int packet;
 
 do_it_again:
 
@@ -1289,16 +1302,19 @@ do_it_again:
                if (mutex_lock_interruptible(&tty->atomic_read_lock))
                        return -ERESTARTSYS;
        }
+       packet = tty->packet;
 
        add_wait_queue(&tty->read_wait, &wait);
        while (nr) {
                /* First test for status change. */
-               if (tty->packet && tty->link->ctrl_status) {
+               if (packet && tty->link->ctrl_status) {
                        unsigned char cs;
                        if (b != buf)
                                break;
+                       spin_lock_irqsave(&tty->link->ctrl_lock, flags);
                        cs = tty->link->ctrl_status;
                        tty->link->ctrl_status = 0;
+                       spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
                        if (tty_put_user(tty, cs, b++)) {
                                retval = -EFAULT;
                                b--;
@@ -1333,6 +1349,7 @@ do_it_again:
                                retval = -ERESTARTSYS;
                                break;
                        }
+                       /* FIXME: does n_tty_set_room need locking ? */
                        n_tty_set_room(tty);
                        timeout = schedule_timeout(timeout);
                        continue;
@@ -1340,7 +1357,7 @@ do_it_again:
                __set_current_state(TASK_RUNNING);
 
                /* Deal with packet mode. */
-               if (tty->packet && b == buf) {
+               if (packet && b == buf) {
                        if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
                                retval = -EFAULT;
                                b--;
@@ -1388,6 +1405,8 @@ do_it_again:
                                break;
                } else {
                        int uncopied;
+                       /* The copy function takes the read lock and handles
+                          locking internally for this case */
                        uncopied = copy_from_read_buf(tty, &b, &nr);
                        uncopied += copy_from_read_buf(tty, &b, &nr);
                        if (uncopied) {
@@ -1429,7 +1448,6 @@ do_it_again:
                 goto do_it_again;
 
        n_tty_set_room(tty);
-
        return retval;
 }