linux-kernel - [PATCH, RFC 09/30] staging: serqt_usb2: don't use sleep

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Date:	Thu,  2 Jan 2014 13:07:33 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-kernel@...r.kernel.org
Cc:	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	devel@...verdev.osuosl.org, Bill Pemberton <wfp5p@...ginia.edu>
Subject: [PATCH, RFC 09/30] staging: serqt_usb2: don't use sleep_on

sleep_on and related functions are going away and should not be used
in this driver any more.

This removes the call to interruptible_sleep_on for a wait queue that
is never woken up, and replaces an interruptible_sleep_on_timeout
call with the equivalent wait_event_interruptible_timeout() to
avoid a small race.

Both call sites still look fishy and need more work.

Signed-off-by: Arnd Bergmann <arndb.de>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: devel@...verdev.osuosl.org
Cc: Bill Pemberton <wfp5p@...ginia.edu>
---
 drivers/staging/serqt_usb2/serqt_usb2.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/staging/serqt_usb2/serqt_usb2.c b/drivers/staging/serqt_usb2/serqt_usb2.c
index 73fc3cc..e0c209e 100644
--- a/drivers/staging/serqt_usb2/serqt_usb2.c
+++ b/drivers/staging/serqt_usb2/serqt_usb2.c
@@ -970,17 +970,11 @@ static void qt_block_until_empty(struct tty_struct *tty,
 {
 	int timeout = HZ / 10;
 	int wait = 30;
-	int count;
-
-	while (1) {
-
-		count = qt_chars_in_buffer(tty);
-
-		if (count <= 0)
-			return;
-
-		interruptible_sleep_on_timeout(&qt_port->wait, timeout);
 
+	/* returns if we get a signal, an error, or the buffer is empty */
+	while (wait_event_interruptible_timeout(qt_port->wait,
+					qt_chars_in_buffer(tty) <= 0,
+					timeout) == 0) {
 		wait--;
 		if (wait == 0) {
 			dev_dbg(&qt_port->port->dev, "%s - TIMEOUT", __func__);
@@ -1137,7 +1131,10 @@ static int qt_ioctl(struct tty_struct *tty,
 
 	if (cmd == TIOCMIWAIT) {
 		while (qt_port != NULL) {
+#if 0
+			/* this never wakes up */
 			interruptible_sleep_on(&qt_port->msr_wait);
+#endif
 			if (signal_pending(current))
 				return -ERESTARTSYS;
 			else {
-- 
1.8.3.2

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