diff -rup --exclude '*SCCS*' --exclude BitKeeper linux.orig/drivers/char/serial.c linux/drivers/char/serial.c
--- linux.orig/drivers/char/serial.c	Wed Mar  9 17:47:18 2005
+++ linux/drivers/char/serial.c	Wed Mar  9 16:40:09 2005
@@ -265,6 +265,9 @@ static int serial_refcount;
 
 static struct timer_list serial_timer;
 
+extern pid_t watched_pid;
+extern void dbg_addmsg(char *fmt, ...);
+
 /* serial subtype definitions */
 #ifndef SERIAL_TYPE_NORMAL
 #define SERIAL_TYPE_NORMAL	1
@@ -2945,10 +2948,13 @@ static void rs_wait_until_sent(struct tt
 	printk("In rs_wait_until_sent(%d) check=%lu...", timeout, char_time);
 	printk("jiff=%lu...", jiffies);
 #endif
+	dbg_addmsg("In rs_wait_until_sent(%d) check=%lu...", timeout, char_time);
+	dbg_addmsg("jiff=%lu...", jiffies);
 	while (!((lsr = serial_inp(info, UART_LSR)) & UART_LSR_TEMT)) {
 #ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
 		printk("lsr = %d (jiff=%lu)...", lsr, jiffies);
 #endif
+		dbg_addmsg("lsr = %d (jiff=%lu)...", lsr, jiffies);
 		set_current_state(TASK_INTERRUPTIBLE);
 		schedule_timeout(char_time);
 		if (signal_pending(current))
@@ -2959,6 +2965,7 @@ static void rs_wait_until_sent(struct tt
 #ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
 	printk("lsr = %d (jiff=%lu)...done\n", lsr, jiffies);
 #endif
+	dbg_addmsg("lsr = %d (jiff=%lu)...done\n", lsr, jiffies);
 }
 
 /*
diff -rup --exclude '*SCCS*' --exclude BitKeeper linux.orig/drivers/char/tty_ioctl.c linux/drivers/char/tty_ioctl.c
--- linux.orig/drivers/char/tty_ioctl.c	Wed Mar  9 17:47:18 2005
+++ linux/drivers/char/tty_ioctl.c	Wed Mar  9 17:15:31 2005
@@ -25,6 +25,16 @@
 #include <asm/uaccess.h>
 #include <asm/system.h>
 
+char dbg_msgbuf[1024*128] = { '\0' };
+char *dbg_msgcur = dbg_msgbuf;
+void dbg_addmsg(char *fmt, ...) {
+    va_list args;
+    va_start(args, fmt);
+    dbg_msgcur += vsprintf(dbg_msgcur, fmt, args);
+    va_end(args);
+}
+
+
 #undef TTY_DEBUG_WAIT_UNTIL_SENT
 
 #undef	DEBUG
@@ -40,11 +50,12 @@ void tty_wait_until_sent(struct tty_stru
 {
 	DECLARE_WAITQUEUE(wait, current);
 
-#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
 	char buf[64];
+#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
 	
 	printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
 #endif
+	dbg_addmsg("%s wait until sent...\n", tty_name(tty, buf));
 	if (!tty->driver.chars_in_buffer)
 		return;
 	add_wait_queue(&tty->write_wait, &wait);
@@ -55,13 +66,19 @@ void tty_wait_until_sent(struct tty_stru
 		printk(KERN_DEBUG "waiting %s...(%d)\n", tty_name(tty, buf),
 		       tty->driver.chars_in_buffer(tty));
 #endif
+		dbg_addmsg("waiting %s...(%d)\n", tty_name(tty, buf),
+			   tty->driver.chars_in_buffer(tty));
 		set_current_state(TASK_INTERRUPTIBLE);
-		if (signal_pending(current))
+		if (signal_pending(current)) {
+			dbg_addmsg("interrupted\n");
 			goto stop_waiting;
+		}
 		if (!tty->driver.chars_in_buffer(tty))
 			break;
 		timeout = schedule_timeout(timeout);
 	} while (timeout);
+	dbg_addmsg("done waiting %s...(%d)\n", tty_name(tty, buf),
+		   tty->driver.chars_in_buffer(tty));
 	if (tty->driver.wait_until_sent)
 		tty->driver.wait_until_sent(tty, timeout);
 stop_waiting: