| Message ID | 1438699259-28508-1-git-send-email-ross.lagerwall@citrix.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Ross Lagerwall <ross.lagerwall@citrix.com> Date: Tue, 4 Aug 2015 15:40:59 +0100 > 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@citrix.com> > --- > Changed in V2: Move wakeup into zerocopy_complete function. Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c index 1a83e19..28577a3 100644 --- a/drivers/net/xen-netback/interface.c +++ b/drivers/net/xen-netback/interface.c @@ -61,6 +61,12 @@ void xenvif_skb_zerocopy_prepare(struct xenvif_queue *queue, void xenvif_skb_zerocopy_complete(struct xenvif_queue *queue) { atomic_dec(&queue->inflight_packets); + + /* Wake the dealloc thread _after_ decrementing inflight_packets so + * that if kthread_stop() has already been called, the dealloc thread + * does not wait forever with nothing to wake it. + */ + wake_up(&queue->dealloc_wq); } int xenvif_schedulable(struct xenvif *vif) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 7d50711..09ffda4 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))
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@citrix.com> --- Changed in V2: Move wakeup into zerocopy_complete function. drivers/net/xen-netback/interface.c | 6 ++++++ drivers/net/xen-netback/netback.c | 1 - 2 files changed, 6 insertions(+), 1 deletion(-)