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xen-netback: don't stop dealloc kthread too early

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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.

Reported-by: Thomas Leonard <talex5@gmail.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Zoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Liu 2014-08-12 11:48:07 +01:00 committed by David S. Miller
parent ea2c5e1342
commit a64bd93452
3 changed files with 42 additions and 7 deletions
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5
drivers/net/xen-netback/common.h
View File

@ -165,6 +165,7 @@ struct xenvif_queue { /* Per-queue data for xenvif */
u16 dealloc_ring[MAX_PENDING_REQS];
struct task_struct *dealloc_task;
wait_queue_head_t dealloc_wq;
atomic_t inflight_packets;
/* Use kthread for guest RX */
struct task_struct *task;
@ -329,4 +330,8 @@ extern unsigned int xenvif_max_queues;
extern struct dentry *xen_netback_dbg_root;
#endif
void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
struct sk_buff *skb);
void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue);
#endif /* __XEN_NETBACK__COMMON_H__ */

18
drivers/net/xen-netback/interface.c
View File

@ -43,6 +43,23 @@
#define XENVIF_QUEUE_LENGTH 32
#define XENVIF_NAPI_WEIGHT 64
/* 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_skb_zerocopy_complete.
*/
void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue,
struct sk_buff *skb)
{
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
atomic_inc(&queue->inflight_packets);
}
void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue)
{
atomic_dec(&queue->inflight_packets);
}
static inline void xenvif_stop_queue(struct xenvif_queue *queue)
{
struct net_device *dev = queue->vif->dev;
@ -557,6 +574,7 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
init_waitqueue_head(&queue->wq);
init_waitqueue_head(&queue->dealloc_wq);
atomic_set(&queue->inflight_packets, 0);
if (tx_evtchn == rx_evtchn) {
/* feature-split-event-channels == 0 */

26
drivers/net/xen-netback/netback.c
View File

@ -1525,10 +1525,12 @@ static int xenvif_handle_frag_list(struct xenvif_queue *queue, struct sk_buff *s
/* remove traces of mapped pages and frag_list */
skb_frag_list_init(skb);
uarg = skb_shinfo(skb)->destructor_arg;
/* increase inflight counter to offset decrement in callback */
atomic_inc(&queue->inflight_packets);
uarg->callback(uarg, true);
skb_shinfo(skb)->destructor_arg = NULL;
skb_shinfo(nskb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
xenvif_skb_zerocopy_prepare(queue, nskb);
kfree_skb(nskb);
return 0;
@ -1589,7 +1591,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
if (net_ratelimit())
netdev_err(queue->vif->dev,
"Not enough memory to consolidate frag_list!\n");
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
xenvif_skb_zerocopy_prepare(queue, skb);
kfree_skb(skb);
continue;
}
@ -1609,7 +1611,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
"Can't setup checksum in net_tx_action\n");
/* We have to set this flag to trigger the callback */
if (skb_shinfo(skb)->destructor_arg)
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
xenvif_skb_zerocopy_prepare(queue, skb);
kfree_skb(skb);
continue;
}
@ -1641,7 +1643,7 @@ static int xenvif_tx_submit(struct xenvif_queue *queue)
* skb. E.g. the __pskb_pull_tail earlier can do such thing.
*/
if (skb_shinfo(skb)->destructor_arg) {
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
xenvif_skb_zerocopy_prepare(queue, skb);
queue->stats.tx_zerocopy_sent++;
}
@ -1681,6 +1683,7 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
queue->stats.tx_zerocopy_success++;
else
queue->stats.tx_zerocopy_fail++;
xenvif_skb_zerocopy_complete(queue);
}
static inline void xenvif_tx_dealloc_action(struct xenvif_queue *queue)
@ -2058,15 +2061,24 @@ int xenvif_kthread_guest_rx(void *data)
return 0;
}
static bool xenvif_dealloc_kthread_should_stop(struct xenvif_queue *queue)
{
/* Dealloc thread must remain running until all inflight
* packets complete.
*/
return kthread_should_stop() &&
!atomic_read(&queue->inflight_packets);
}
int xenvif_dealloc_kthread(void *data)
{
struct xenvif_queue *queue = data;
while (!kthread_should_stop()) {
for (;;) {
wait_event_interruptible(queue->dealloc_wq,
tx_dealloc_work_todo(queue) ||
kthread_should_stop());
if (kthread_should_stop())
xenvif_dealloc_kthread_should_stop(queue));
if (xenvif_dealloc_kthread_should_stop(queue))
break;
xenvif_tx_dealloc_action(queue);