[patch] sched, tty: fix scheduling latencies in tty_io.c

[Ingo Molnar]

the attached patch fixes long scheduling latencies in tty_read() and 
tty_write() caused by the BKL.

has been tested as part of the -VP patchset and the tty_read() side 
has also been tested in earlier -mm trees.

	Ingo

the attached patch fixes long scheduling latencies in tty_read() and
tty_write() caused by the BKL.

has been tested as part of the -VP patchset and the tty_read() side
has also been tested in earlier -mm trees.

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>

--- linux/drivers/char/tty_io.c.orig	
+++ linux/drivers/char/tty_io.c	
@@ -660,12 +660,10 @@ static ssize_t tty_read(struct file * fi
 	if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
 		return -EIO;
 
-	lock_kernel();
 	if (tty->ldisc.read)
 		i = (tty->ldisc.read)(tty,file,buf,count);
 	else
 		i = -EIO;
-	unlock_kernel();
 	if (i > 0)
 		inode->i_atime = CURRENT_TIME;
 	return i;
@@ -688,17 +686,13 @@ static inline ssize_t do_tty_write(
 		return -ERESTARTSYS;
 	}
 	if ( test_bit(TTY_NO_WRITE_SPLIT, &tty->flags) ) {
-		lock_kernel();
 		written = write(tty, file, buf, count);
-		unlock_kernel();
 	} else {
 		for (;;) {
 			unsigned long size = max((unsigned long)PAGE_SIZE*2, 16384UL);
 			if (size > count)
 				size = count;
-			lock_kernel();
 			ret = write(tty, file, buf, size);
-			unlock_kernel();
 			if (ret <= 0)
 				break;
 			written += ret;