Re: patch "TTY: remove tty_locked" added to tty tree

[Jiri Slaby <jslaby@suse.cz>]

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On 08/23/2011 07:36 PM, gregkh@suse.de wrote:
> diff --git a/include/linux/tty.h b/include/linux/tty.h
> index 44bc0c5..6d5eceb 100644
> --- a/include/linux/tty.h
> +++ b/include/linux/tty.h
> @@ -600,8 +600,6 @@ extern long vt_compat_ioctl(struct tty_struct *tty,
>  /* functions for preparation of BKL removal */
>  extern void __lockfunc tty_lock(void) __acquires(tty_lock);
>  extern void __lockfunc tty_unlock(void) __releases(tty_lock);
> -extern struct task_struct *__big_tty_mutex_owner;
> -#define tty_locked()		(current == __big_tty_mutex_owner)

It looks like I need tty_locked to fix system stalls in
tty_wait_until_sent in the end. Like with the patch attached. But if
someone finds another way to fix this in short-term, it would be great.

thanks,
-- 
js
suse labs

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>From a7c35daffe26129072aceb5d285924017820b56d Mon Sep 17 00:00:00 2001
From: Jiri Slaby <jslaby@suse.cz>
Date: Fri, 19 Aug 2011 22:16:51 +0200
Subject: [PATCH] TTY: fix stalls on BTM when waiting until sent

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Andreas Bombe <aeb@debian.org>
---
 drivers/tty/tty_ioctl.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/tty_ioctl.c b/drivers/tty/tty_ioctl.c
index 53f2442..3837175 100644
--- a/drivers/tty/tty_ioctl.c
+++ b/drivers/tty/tty_ioctl.c
@@ -146,6 +146,7 @@ EXPORT_SYMBOL(tty_unthrottle);
 
 void tty_wait_until_sent(struct tty_struct *tty, long timeout)
 {
+	int retval;
 #ifdef TTY_DEBUG_WAIT_UNTIL_SENT
 	char buf[64];
 
@@ -153,8 +154,14 @@ void tty_wait_until_sent(struct tty_struct *tty, long timeout)
 #endif
 	if (!timeout)
 		timeout = MAX_SCHEDULE_TIMEOUT;
-	if (wait_event_interruptible_timeout(tty->write_wait,
-			!tty_chars_in_buffer(tty), timeout) >= 0) {
+
+	if (tty_locked()) /* e.g. uart (holds) vs. tty_ioctl (does not) */
+		retval = wait_event_interruptible_timeout_tty(tty->write_wait,
+			!tty_chars_in_buffer(tty), timeout);
+	else
+		retval = wait_event_interruptible_timeout(tty->write_wait,
+			!tty_chars_in_buffer(tty), timeout);
+	if (retval >= 0) {
 		if (tty->ops->wait_until_sent)
 			tty->ops->wait_until_sent(tty, timeout);
 	}
-- 
1.7.6