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tun: don't look at current when non-blocking

PATCH In review Michael S. Tsirkin 3 participants 6 messages Oct 6, 2013 – Oct 9, 2013

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Networking Network drivers TUN/TAP driver
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Michael S. Tsirkin

author
#0 lore raw

PATCH 1/1 tun: don't look at current when non-blocking

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 protected]>
---
 drivers/net/tun.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
drivers/net/tun.c +5 -3
index 807815f..7cb105c 100644
@@ -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;
 }
Signature · 1 line
MST
Acked-by on v1 1/1
#1 lore raw
Quoted 7 lines · Michael S. Tsirkin

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 protected]>

---

Acked-by Jason Wang <[email protected]>
Quoted 30 lines
 drivers/net/tun.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)
drivers/net/tun.c +5 -3
index 807815f..7cb105c 100644
@@ -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;
 }
#3 lore raw
Quoted 11 lines · David Miller

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

Quoted 6 lines

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 protected]>

Applied and queued up for -stable, thanks.
--

Michael, I believe this is just an optimization or a required patch of your following patches. So no need go for stable?

author
#4 lore raw
Quoted 9 lines · Jason Wang
Quoted 8 lines · David Miller

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

Quoted 5 lines

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.

Quoted 6 lines
Quoted 3 lines
Quoted 1 line
Signed-off-by Michael S. Tsirkin <[email protected]>

Applied and queued up for -stable, thanks.
--

Michael, I believe this is just an optimization or a required patch of your following patches. So no need go for stable?

I don't think it's required for stable.

maintainer
#5 lore raw

From: "Michael S. Tsirkin" <[email protected]>
Date: Wed, 9 Oct 2013 11:13:54 +0300

Quoted 10 lines · Jason Wang
Quoted 9 lines · David Miller
Quoted 8 lines

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

Quoted 5 lines

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.

Quoted 8 lines
Quoted 6 lines
Quoted 3 lines
Quoted 1 line
Signed-off-by Michael S. Tsirkin <[email protected]>

Applied and queued up for -stable, thanks.
--

Michael, I believe this is just an optimization or a required patch of your following patches. So no need go for stable?

I don't think it's required for stable.

Ok, removed from the -stable queue. Thanks.