Subject: [PATCH] tun: don't look at current when non-blocking

From: "Michael S. Tsirkin" <[email-masked]>
Date: Sun, 6 Oct 2013 21:25:12 +0300

We play with a wait queue even if socket is
non blocking. This is an obvious waste.
Besides, it will prevent calling the non blocking
variant when current is not valid.

Signed-off-by: Michael S. Tsirkin <[email-masked]>
---
 drivers/net/tun.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 807815f..7cb105c 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1293,7 +1293,8 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
 	if (unlikely(!noblock))
 		add_wait_queue(&tfile->wq.wait, &wait);
 	while (len) {
-		current->state = TASK_INTERRUPTIBLE;
+		if (unlikely(!noblock))
+			current->state = TASK_INTERRUPTIBLE;
 
 		/* Read frames from the queue */
 		if (!(skb = skb_dequeue(&tfile->socket.sk->sk_receive_queue))) {
@@ -1320,9 +1321,10 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
 		break;
 	}
 
-	current->state = TASK_RUNNING;
-	if (unlikely(!noblock))
+	if (unlikely(!noblock)) {
+		current->state = TASK_RUNNING;
 		remove_wait_queue(&tfile->wq.wait, &wait);
+	}
 
 	return ret;
 }
-- 
MST