X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=drivers%2Fchar%2Ftty_io.c;h=9c867cf6de6456293314eb1675e697c87a9f64d2;hb=b1b8aca480a26efb21168e311e8025a22b042591;hp=de37ebc3a4cf03fa9e94d68fbf7e0f70b9293337;hpb=22aadf8a07067644e101267ed5003043f2ad05bf;p=linux-2.6

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index de37ebc3a4..9c867cf6de 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -369,25 +369,54 @@ static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
 }
 
 /**
- *	tty_buffer_flush		-	flush full tty buffers
+ *	__tty_buffer_flush		-	flush full tty buffers
  *	@tty: tty to flush
  *
- *	flush all the buffers containing receive data
+ *	flush all the buffers containing receive data. Caller must
+ *	hold the buffer lock and must have ensured no parallel flush to
+ *	ldisc is running.
  *
- *	Locking: none
+ *	Locking: Caller must hold tty->buf.lock
  */
 
-static void tty_buffer_flush(struct tty_struct *tty)
+static void __tty_buffer_flush(struct tty_struct *tty)
 {
 	struct tty_buffer *thead;
-	unsigned long flags;
 
-	spin_lock_irqsave(&tty->buf.lock, flags);
 	while((thead = tty->buf.head) != NULL) {
 		tty->buf.head = thead->next;
 		tty_buffer_free(tty, thead);
 	}
 	tty->buf.tail = NULL;
+}
+
+/**
+ *	tty_buffer_flush		-	flush full tty buffers
+ *	@tty: tty to flush
+ *
+ *	flush all the buffers containing receive data. If the buffer is
+ *	being processed by flush_to_ldisc then we defer the processing
+ *	to that function
+ *
+ *	Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&tty->buf.lock, flags);
+
+	/* If the data is being pushed to the tty layer then we can't
+	   process it here. Instead set a flag and the flush_to_ldisc
+	   path will process the flush request before it exits */
+	if (test_bit(TTY_FLUSHING, &tty->flags)) {
+		set_bit(TTY_FLUSHPENDING, &tty->flags);
+		spin_unlock_irqrestore(&tty->buf.lock, flags);
+		wait_event(tty->read_wait,
+				test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
+		return;
+	} else
+		__tty_buffer_flush(tty);
 	spin_unlock_irqrestore(&tty->buf.lock, flags);
 }
 
@@ -2034,8 +2063,7 @@ static int init_dev(struct tty_driver *driver, int idx,
 	}
 
 	if (!*tp_loc) {
-		tp = (struct ktermios *) kmalloc(sizeof(struct ktermios),
-						GFP_KERNEL);
+		tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
 		if (!tp)
 			goto free_mem_out;
 		*tp = driver->init_termios;
@@ -2065,8 +2093,7 @@ static int init_dev(struct tty_driver *driver, int idx,
 		}
 
 		if (!*o_tp_loc) {
-			o_tp = (struct ktermios *)
-				kmalloc(sizeof(struct ktermios), GFP_KERNEL);
+			o_tp = kmalloc(sizeof(struct ktermios), GFP_KERNEL);
 			if (!o_tp)
 				goto free_mem_out;
 			*o_tp = driver->other->init_termios;
@@ -3594,6 +3621,7 @@ static void flush_to_ldisc(struct work_struct *work)
 		return;
 
 	spin_lock_irqsave(&tty->buf.lock, flags);
+	set_bit(TTY_FLUSHING, &tty->flags);	/* So we know a flush is running */
 	head = tty->buf.head;
 	if (head != NULL) {
 		tty->buf.head = NULL;
@@ -3607,6 +3635,11 @@ static void flush_to_ldisc(struct work_struct *work)
 				tty_buffer_free(tty, tbuf);
 				continue;
 			}
+			/* Ldisc or user is trying to flush the buffers
+			   we are feeding to the ldisc, stop feeding the
+			   line discipline as we want to empty the queue */
+			if (test_bit(TTY_FLUSHPENDING, &tty->flags))
+				break;
 			if (!tty->receive_room) {
 				schedule_delayed_work(&tty->buf.work, 1);
 				break;
@@ -3620,8 +3653,17 @@ static void flush_to_ldisc(struct work_struct *work)
 			disc->receive_buf(tty, char_buf, flag_buf, count);
 			spin_lock_irqsave(&tty->buf.lock, flags);
 		}
+		/* Restore the queue head */
 		tty->buf.head = head;
 	}
+	/* We may have a deferred request to flush the input buffer,
+	   if so pull the chain under the lock and empty the queue */
+	if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
+		__tty_buffer_flush(tty);
+		clear_bit(TTY_FLUSHPENDING, &tty->flags);
+		wake_up(&tty->read_wait);
+	}
+	clear_bit(TTY_FLUSHING, &tty->flags);
 	spin_unlock_irqrestore(&tty->buf.lock, flags);
 
 	tty_ldisc_deref(disc);