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Date:	Tue, 4 Aug 2015 13:50:58 +0100
From:	Ross Lagerwall <ross.lagerwall@...rix.com>
To:	<netdev@...r.kernel.org>
CC:	<xen-devel@...ts.xenproject.org>, Wei Liu <wei.liu2@...rix.com>,
	"Ian Campbell" <ian.campbell@...rix.com>,
	Ross Lagerwall <ross.lagerwall@...rix.com>
Subject: [PATCH] xen/netback: Wake dealloc thread after completing zerocopy work

Waking the dealloc thread before decrementing inflight_packets is racy
because it means the thread may go to sleep before inflight_packets is
decremented. If kthread_stop() has already been called, the dealloc
thread may wait forever with nothing to wake it. Instead, wake the
thread only after decrementing inflight_packets.

Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com>
---
 drivers/net/xen-netback/netback.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 7d50711..e95ee20 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -1536,7 +1536,6 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
 		smp_wmb();
 		queue->dealloc_prod++;
 	} while (ubuf);
-	wake_up(&queue->dealloc_wq);
 	spin_unlock_irqrestore(&queue->callback_lock, flags);
 
 	if (likely(zerocopy_success))
@@ -1544,6 +1543,7 @@ void xenvif_zerocopy_callback(struct ubuf_info *ubuf, bool zerocopy_success)
 	else
 		queue->stats.tx_zerocopy_fail++;
 	xenvif_skb_zerocopy_complete(queue);
+	wake_up(&queue->dealloc_wq);
 }
 
 static inline void xenvif_tx_dealloc_action(struct xenvif_queue *queue)
-- 
2.1.0

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