From: David Vrabel <david.vrabel@citrix•com>
To: Wei Liu <wei.liu2@citrix•com>, <netdev@vger•kernel.org>,
<xen-devel@lists•xen.org>
Cc: Ian Campbell <ian.campbell@citrix•com>,
Zoltan Kiss <zoltan.kiss@citrix•com>
Subject: Re: [Xen-devel] [PATCH net v2 2/3] xen-netback: don't stop dealloc kthread too early
Date: Mon, 11 Aug 2014 13:10:12 +0100 [thread overview]
Message-ID: <53E8B2A4.9070008@citrix.com> (raw)
In-Reply-To: <1407515833-2550-3-git-send-email-wei.liu2@citrix.com>
On 08/08/14 17:37, Wei Liu wrote:
> Reference count the number of packets in host stack, so that we don't
> stop the deallocation thread too early. If not, we can end up with
> xenvif_free permanently waiting for deallocation thread to unmap grefs.
[...]
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -43,6 +43,17 @@
> #define XENVIF_QUEUE_LENGTH 32
> #define XENVIF_NAPI_WEIGHT 64
>
> +void xenvif_inc_inflight_packets(struct xenvif_queue *queue)
> +{
> + atomic_inc(&queue->inflight_packets);
> +}
> +
> +void xenvif_dec_inflight_packets(struct xenvif_queue *queue)
> +{
> + if (atomic_dec_and_test(&queue->inflight_packets))
> + wake_up(&queue->inflight_wq);
> +}
You don't need these wrappers if you remove the inflight_wq (see below).
> static inline void xenvif_stop_queue(struct xenvif_queue *queue)
> {
> struct net_device *dev = queue->vif->dev;
> @@ -561,6 +572,8 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
>
> init_waitqueue_head(&queue->wq);
> init_waitqueue_head(&queue->dealloc_wq);
> + init_waitqueue_head(&queue->inflight_wq);
> + atomic_set(&queue->inflight_packets, 0);
>
> if (tx_evtchn == rx_evtchn) {
> /* feature-split-event-channels == 0 */
> @@ -687,6 +700,9 @@ void xenvif_disconnect(struct xenvif *vif)
> queue->task = NULL;
> }
>
> + wait_event(queue->inflight_wq,
> + atomic_read(&queue->inflight_packets) == 0);
Just make the dealloc task not stop unless it has deallocated all
outstanding requests. There's no need for another wait queue here.
> +
> if (queue->dealloc_task) {
> kthread_stop(queue->dealloc_task);
> queue->dealloc_task = NULL;
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 4734472..d2f0c7d7 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -107,6 +107,18 @@ static inline unsigned long idx_to_kaddr(struct xenvif_queue *queue,
> #define callback_param(vif, pending_idx) \
> (vif->pending_tx_info[pending_idx].callback_struct)
>
> +/* This function is used to set SKBTX_DEV_ZEROCOPY as well as
> + * increasing the inflight counter. We need to increase the inflight
> + * counter because core driver calls into xenvif_zerocopy_callback
> + * which calls xenvif_dec_inflight_packets.
> + */
> +static void set_skb_zerocopy(struct xenvif_queue *queue,
> + struct sk_buff *skb)
> +{
> + skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
> + xenvif_inc_inflight_packets(queue);
> +}
This name makes this look like a core function instead of a netback
specific one.
I would suggest a pair of functions:
xenvif_skb_zerocopy_prepare()
xenvif_skb_zerocopy_complete()
Or similar.
David
next prev parent reply other threads:[~2014-08-11 12:10 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-08 16:37 [PATCH net v2 0/3] xen-netback: synchronisation between core driver and netback Wei Liu
2014-08-08 16:37 ` [PATCH net v2 1/3] xen-netback: move NAPI add/remove calls Wei Liu
2014-08-08 16:49 ` Sergei Shtylyov
2014-08-08 16:52 ` Wei Liu
2014-08-11 12:35 ` [Xen-devel] " David Vrabel
2014-08-11 12:49 ` Zoltan Kiss
2014-08-11 13:01 ` David Vrabel
2014-08-11 13:14 ` Zoltan Kiss
2014-08-11 13:43 ` Wei Liu
2014-08-11 13:59 ` David Vrabel
2014-08-11 14:08 ` Wei Liu
2014-08-08 16:37 ` [PATCH net v2 2/3] xen-netback: don't stop dealloc kthread too early Wei Liu
2014-08-11 12:10 ` David Vrabel [this message]
2014-08-11 13:48 ` [Xen-devel] " Wei Liu
2014-08-11 13:58 ` David Vrabel
2014-08-11 14:13 ` Zoltan Kiss
2014-08-11 14:44 ` Wei Liu
2014-08-11 15:23 ` David Vrabel
2014-08-11 20:39 ` Wei Liu
2014-08-11 14:31 ` Wei Liu
2014-08-11 14:34 ` David Vrabel
2014-08-11 14:39 ` Wei Liu
2014-08-08 16:37 ` [PATCH net v2 3/3] xen-netback: remove loop waiting function Wei Liu
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