Merge branch 'uprobes-v7' of git://git.linaro.org/people/dave.long/linux into devel-stable

This patch series adds basic uprobes support to ARM. It is based on
patches developed earlier by Rabin Vincent. That approach of adding
hooks into the kprobes instruction parsing code was not well received.
This approach separates the ARM instruction parsing code in kprobes out
into a separate set of functions which can be used by both kprobes and
uprobes. Both kprobes and uprobes then provide their own semantic action
tables to process the results of the parsing.

1 files changed, 26 insertions, 21 deletions

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 9a68409580d5..a0fa5de210cf 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -70,7 +70,12 @@ enum {
 };
 
 struct vhost_net_ubuf_ref {
-        struct kref kref;
+        /* refcount follows semantics similar to kref:
+         *  0: object is released
+         *  1: no outstanding ubufs
+         * >1: outstanding ubufs
+         */
+        atomic_t refcount;
         wait_queue_head_t wait;
         struct vhost_virtqueue *vq;
 };
@@ -116,14 +121,6 @@ static void vhost_net_enable_zcopy(int vq)
         vhost_net_zcopy_mask |= 0x1 << vq;
 }
 
-static void vhost_net_zerocopy_done_signal(struct kref *kref)
-{
-        struct vhost_net_ubuf_ref *ubufs;
-
-        ubufs = container_of(kref, struct vhost_net_ubuf_ref, kref);
-        wake_up(&ubufs->wait);
-}
-
 static struct vhost_net_ubuf_ref *
 vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
 {
@@ -134,21 +131,24 @@ vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
         ubufs = kmalloc(sizeof(*ubufs), GFP_KERNEL);
         if (!ubufs)
                 return ERR_PTR(-ENOMEM);
-        kref_init(&ubufs->kref);
+        atomic_set(&ubufs->refcount, 1);
         init_waitqueue_head(&ubufs->wait);
         ubufs->vq = vq;
         return ubufs;
 }
 
-static void vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
+static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
 {
-        kref_put(&ubufs->kref, vhost_net_zerocopy_done_signal);
+        int r = atomic_sub_return(1, &ubufs->refcount);
+        if (unlikely(!r))
+                wake_up(&ubufs->wait);
+        return r;
 }
 
 static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)
 {
-        kref_put(&ubufs->kref, vhost_net_zerocopy_done_signal);
-        wait_event(ubufs->wait, !atomic_read(&ubufs->kref.refcount));
+        vhost_net_ubuf_put(ubufs);
+        wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));
 }
 
 static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
@@ -306,23 +306,26 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
 {
         struct vhost_net_ubuf_ref *ubufs = ubuf->ctx;
         struct vhost_virtqueue *vq = ubufs->vq;
-        int cnt = atomic_read(&ubufs->kref.refcount);
+        int cnt;
+
+        rcu_read_lock_bh();
 
         /* set len to mark this desc buffers done DMA */
         vq->heads[ubuf->desc].len = success ?
                 VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
-        vhost_net_ubuf_put(ubufs);
+        cnt = vhost_net_ubuf_put(ubufs);
 
         /*
          * Trigger polling thread if guest stopped submitting new buffers:
-         * in this case, the refcount after decrement will eventually reach 1
-         * so here it is 2.
+         * in this case, the refcount after decrement will eventually reach 1.
          * We also trigger polling periodically after each 16 packets
          * (the value 16 here is more or less arbitrary, it's tuned to trigger
          * less than 10% of times).
          */
-        if (cnt <= 2 || !(cnt % 16))
+        if (cnt <= 1 || !(cnt % 16))
                 vhost_poll_queue(&vq->poll);
+
+        rcu_read_unlock_bh();
 }
 
 /* Expects to be always run from workqueue - which acts as
@@ -420,7 +423,7 @@ static void handle_tx(struct vhost_net *net)
                         msg.msg_control = ubuf;
                         msg.msg_controllen = sizeof(ubuf);
                         ubufs = nvq->ubufs;
-                        kref_get(&ubufs->kref);
+                        atomic_inc(&ubufs->refcount);
                         nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
                 } else {
                         msg.msg_control = NULL;
@@ -780,7 +783,7 @@ static void vhost_net_flush(struct vhost_net *n)
                 vhost_net_ubuf_put_and_wait(n->vqs[VHOST_NET_VQ_TX].ubufs);
                 mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
                 n->tx_flush = false;
-                kref_init(&n->vqs[VHOST_NET_VQ_TX].ubufs->kref);
+                atomic_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);
                 mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
         }
 }
@@ -800,6 +803,8 @@ static int vhost_net_release(struct inode *inode, struct file *f)
                 fput(tx_sock->file);
         if (rx_sock)
                 fput(rx_sock->file);
+        /* Make sure no callbacks are outstanding */
+        synchronize_rcu_bh();
         /* We do an extra flush before freeing memory,
          * since jobs can re-queue themselves. */
         vhost_net_flush(n);