[PATCH 1/3] kvm tools: Make virtio-net kvm__irq_line thread safe

[Asias He <asias.hejun@gmail.com>]

This patch fixes virtio-net randmom stall

host $ scp guest:/root/big.guest .
big.guest 42%  440MB  67.7KB/s - stalled -

Signed-off-by: Asias He <asias.hejun@gmail.com>
---
 tools/kvm/virtio-net.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/virtio-net.c b/tools/kvm/virtio-net.c
index 58b3de4..efe06cb 100644
--- a/tools/kvm/virtio-net.c
+++ b/tools/kvm/virtio-net.c
@@ -77,9 +77,12 @@ static void virtio_net_rx_callback(struct kvm *self, void *param)
 		head = virt_queue__get_iov(vq, iov, &out, &in, self);
 		len = readv(net_device.tap_fd, iov, in);
 		virt_queue__set_used_elem(vq, head, len);
-	}
 
-	kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
+		/* We should interrupt guest right now, otherwise latency is huge. */
+		mutex_lock(&net_device.mutex);
+		kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
+		mutex_unlock(&net_device.mutex);
+	}
 }
 
 static void virtio_net_tx_callback(struct kvm *self, void *param)
@@ -98,7 +101,9 @@ static void virtio_net_tx_callback(struct kvm *self, void *param)
 		virt_queue__set_used_elem(vq, head, len);
 	}
 
+	mutex_lock(&net_device.mutex);
 	kvm__irq_line(self, VIRTIO_NET_IRQ, 1);
+	mutex_unlock(&net_device.mutex);
 }
 
 static bool virtio_net_pci_io_device_specific_in(void *data, unsigned long offset, int size, uint32_t count)
-- 
1.7.4.4