the attached patch fixes long scheduling latencies in pty_read()caused
by the BKL.

has been tested as part of the -VP patchset and in earlier -mm trees.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

--- linux/drivers/char/pty.c.orig	
+++ linux/drivers/char/pty.c	
@@ -139,6 +139,7 @@ static int pty_write(struct tty_struct *
 			c     += n;
 			count -= n;
 			to->ldisc.receive_buf(to, temp_buffer, NULL, n);
+			cond_resched();
 		}
 		up(&tty->flip.pty_sem);
 	} else {