PERFORCE change 150382 for review

[Ed Schouten]

http://perforce.freebsd.org/chv.cgi?CH=150382

Change 150382 by ed at ed_dull on 2008/09/24 11:49:24

	- Don't call ttydev_leave() when tty_unlock() is good enough.
	- Correct error codes of read() and write() calls.

Affected files ...

.. //depot/projects/mpsafetty/sys/kern/tty.c#44 edit

Differences ...

==== //depot/projects/mpsafetty/sys/kern/tty.c#44 (text+ko) ====

@@ -133,11 +133,12 @@
 }
 
 /*
- * Because the revoke() call already calls d_close() without making sure
- * all threads are purged from the TTY, we can only destroy the buffers
- * and such when the last thread leaves the TTY. ttydev_enter() and
- * ttydev_leave() are called from within the cdev functions, to make
- * sure we can garbage collect the TTY.
+ * Though ttydev_enter() and ttydev_leave() seem to be related, they
+ * don't have to be used together. ttydev_enter() is used by the cdev
+ * operations to prevent an actual from being processed when the TTY has
+ * been abandoned. ttydev_leave() is used by ttydev_open() and
+ * ttydev_close() to determine whether per-TTY data should be
+ * deallocated.
  */
 
 static __inline int
@@ -287,6 +288,7 @@
 
 done:	tp->t_flags &= ~TF_OPENCLOSE;
 	ttydev_leave(tp);
+
 	return (error);
 }
 
@@ -378,22 +380,23 @@
 
 	error = ttydev_enter(tp);
 	if (error)
-		return (0);
+		goto done;
 
 	error = tty_wait_background(tp, curthread, SIGTTIN);
-	if (error)
+	if (error) {
+		tty_unlock(tp);
 		goto done;
+	}
 
 	error = ttydisc_read(tp, uio, ioflag);
-done:	ttydev_leave(tp);
+	tty_unlock(tp);
 
 	/*
-	 * The read() and write() calls should not throw an error when
-	 * the device is ripped offline.
+	 * The read() call should not throw an error when the device is
+	 * being destroyed. Silently convert it to an EOF.
 	 */
-	if (error == ENXIO)
-		return (0);
-
+done:	if (error == ENXIO)
+		error = 0;
 	return (error);
 }
 
@@ -405,24 +408,19 @@
 
 	error = ttydev_enter(tp);
 	if (error)
-		return (0);
+		return (error);
 
 	if (tp->t_termios.c_lflag & TOSTOP) {
 		error = tty_wait_background(tp, curthread, SIGTTOU);
-		if (error)
-			goto done;
+		if (error) {
+			tty_unlock(tp);
+			return (error);
+		}
 	}
 
 	error = ttydisc_write(tp, uio, ioflag);
-done:	ttydev_leave(tp);
+	tty_unlock(tp);
 
-	/*
-	 * The read() and write() calls should not throw an error when
-	 * the device is ripped offline.
-	 */
-	if (error == ENXIO)
-		return (0);
-
 	return (error);
 }
 
@@ -479,7 +477,7 @@
 	}
 
 	error = tty_ioctl(tp, cmd, data, td);
-done:	ttydev_leave(tp);
+done:	tty_unlock(tp);
 
 	return (error);
 }
@@ -518,7 +516,7 @@
 			selrecord(td, &tp->t_outpoll);
 	}
 
-	ttydev_leave(tp);
+	tty_unlock(tp);
 
 	return (revents);
 }
@@ -535,7 +533,7 @@
 	if (error)
 		return (-1);
 	error = ttydevsw_mmap(tp, offset, paddr, nprot);
-	ttydev_leave(tp);
+	tty_unlock(tp);
 
 	return (error);
 }
@@ -623,7 +621,7 @@
 		break;
 	}
 
-	ttydev_leave(tp);
+	tty_unlock(tp);
 	return (error);
 }