linux-kernel - Re: [PATCH] tun: don't look at current when non-blocking

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Message-ID: <525372EF.9090307@redhat.com>
Date:	Tue, 08 Oct 2013 10:50:23 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
CC:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [PATCH] tun: don't look at current when non-blocking

On 10/07/2013 02:25 AM, Michael S. Tsirkin wrote:
> 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 <mst@...hat.com>
> ---

Acked-by: Jason Wang <jasowang@...hat.com>
>  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;
>  }

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