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vhost: fix IOTLB locking

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Commit 78139c94dc ("net: vhost: lock the vqs one by one") moved the vq
lock to improve scalability, but introduced a possible deadlock in
vhost-iotlb. vhost_iotlb_notify_vq() now takes vq->mutex while holding
the device's IOTLB spinlock. And on the vhost_iotlb_miss() path, the
spinlock is taken while holding vq->mutex.

Since calling vhost_poll_queue() doesn't require any lock, avoid the
deadlock by not taking vq->mutex.

Fixes: 78139c94dc ("net: vhost: lock the vqs one by one")
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jean-Philippe Brucker 2018-11-30 16:05:53 +00:00 committed by David S. Miller
parent 4763c9f926
commit e3f787189e
1 changed files with 0 additions and 3 deletions
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3
drivers/vhost/vhost.c
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@ -944,10 +944,7 @@ static void vhost_iotlb_notify_vq(struct vhost_dev *d,
if (msg->iova <= vq_msg->iova &&
msg->iova + msg->size - 1 >= vq_msg->iova &&
vq_msg->type == VHOST_IOTLB_MISS) {
mutex_lock(&node->vq->mutex);
vhost_poll_queue(&node->vq->poll);
mutex_unlock(&node->vq->mutex);
list_del(&node->node);
kfree(node);
}