diff options
author | Zoltan Kiss <zoltan.kiss@citrix.com> | 2014-02-04 19:54:37 +0000 |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2014-02-05 16:24:08 -0800 |
commit | 9ab9831b4c59d379a17f92a6157c7e921811dea2 (patch) | |
tree | db1279d7fcd1847180cc22dc15a809de048509f8 /drivers | |
parent | bce3ea81d5b2a33ed0e275d58a45f10ce95cbd50 (diff) | |
download | linux-9ab9831b4c59d379a17f92a6157c7e921811dea2.tar.bz2 |
xen-netback: Fix Rx stall due to race condition
The recent patch to fix receive side flow control
(11b57f90257c1d6a91cee720151b69e0c2020cf6: xen-netback: stop vif thread
spinning if frontend is unresponsive) solved the spinning thread problem,
however caused an another one. The receive side can stall, if:
- [THREAD] xenvif_rx_action sets rx_queue_stopped to true
- [INTERRUPT] interrupt happens, and sets rx_event to true
- [THREAD] then xenvif_kthread sets rx_event to false
- [THREAD] rx_work_todo doesn't return true anymore
Also, if interrupt sent but there is still no room in the ring, it take quite a
long time until xenvif_rx_action realize it. This patch ditch that two variable,
and rework rx_work_todo. If the thread finds it can't fit more skb's into the
ring, it saves the last slot estimation into rx_last_skb_slots, otherwise it's
kept as 0. Then rx_work_todo will check if:
- there is something to send to the ring (like before)
- there is space for the topmost packet in the queue
I think that's more natural and optimal thing to test than two bool which are
set somewhere else.
Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/net/xen-netback/common.h | 6 | ||||
-rw-r--r-- | drivers/net/xen-netback/interface.c | 1 | ||||
-rw-r--r-- | drivers/net/xen-netback/netback.c | 16 |
3 files changed, 7 insertions, 16 deletions
diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-netback/common.h index 4c76bcb9a879..ae413a2cbee7 100644 --- a/drivers/net/xen-netback/common.h +++ b/drivers/net/xen-netback/common.h @@ -143,11 +143,7 @@ struct xenvif { char rx_irq_name[IFNAMSIZ+4]; /* DEVNAME-rx */ struct xen_netif_rx_back_ring rx; struct sk_buff_head rx_queue; - bool rx_queue_stopped; - /* Set when the RX interrupt is triggered by the frontend. - * The worker thread may need to wake the queue. - */ - bool rx_event; + RING_IDX rx_last_skb_slots; /* This array is allocated seperately as it is large */ struct gnttab_copy *grant_copy_op; diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index b9de31ea7fc4..7669d49a67e2 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -100,7 +100,6 @@ static irqreturn_t xenvif_rx_interrupt(int irq, void *dev_id) { struct xenvif *vif = dev_id; - vif->rx_event = true; xenvif_kick_thread(vif); return IRQ_HANDLED; diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 6b62c3eb8e18..e5284bca2d90 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -476,7 +476,6 @@ static void xenvif_rx_action(struct xenvif *vif) unsigned long offset; struct skb_cb_overlay *sco; bool need_to_notify = false; - bool ring_full = false; struct netrx_pending_operations npo = { .copy = vif->grant_copy_op, @@ -486,7 +485,7 @@ static void xenvif_rx_action(struct xenvif *vif) skb_queue_head_init(&rxq); while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) { - int max_slots_needed; + RING_IDX max_slots_needed; int i; /* We need a cheap worse case estimate for the number of @@ -509,9 +508,10 @@ static void xenvif_rx_action(struct xenvif *vif) if (!xenvif_rx_ring_slots_available(vif, max_slots_needed)) { skb_queue_head(&vif->rx_queue, skb); need_to_notify = true; - ring_full = true; + vif->rx_last_skb_slots = max_slots_needed; break; - } + } else + vif->rx_last_skb_slots = 0; sco = (struct skb_cb_overlay *)skb->cb; sco->meta_slots_used = xenvif_gop_skb(skb, &npo); @@ -522,8 +522,6 @@ static void xenvif_rx_action(struct xenvif *vif) BUG_ON(npo.meta_prod > ARRAY_SIZE(vif->meta)); - vif->rx_queue_stopped = !npo.copy_prod && ring_full; - if (!npo.copy_prod) goto done; @@ -1473,8 +1471,8 @@ static struct xen_netif_rx_response *make_rx_response(struct xenvif *vif, static inline int rx_work_todo(struct xenvif *vif) { - return (!skb_queue_empty(&vif->rx_queue) && !vif->rx_queue_stopped) || - vif->rx_event; + return !skb_queue_empty(&vif->rx_queue) && + xenvif_rx_ring_slots_available(vif, vif->rx_last_skb_slots); } static inline int tx_work_todo(struct xenvif *vif) @@ -1560,8 +1558,6 @@ int xenvif_kthread(void *data) if (!skb_queue_empty(&vif->rx_queue)) xenvif_rx_action(vif); - vif->rx_event = false; - if (skb_queue_empty(&vif->rx_queue) && netif_queue_stopped(vif->dev)) xenvif_start_queue(vif); |