Re: [Xen-devel] [PATCH v4 13/18] xen/pvcalls: implement release command

[Stefano Stabellini]

On Tue, 20 Jun 2017, Boris Ostrovsky wrote:
> > +
> > +static int pvcalls_back_release_passive(struct xenbus_device *dev,
> > +   struct pvcalls_fedata *fedata,
> > +   struct sockpass_mapping *mappass)
> > +{
> > +   if (mappass->sock->sk != NULL) {
> > +   write_lock_bh(>sock->sk->sk_callback_lock);
> > +   mappass->sock->sk->sk_user_data = NULL;
> > +   mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
> > +   write_unlock_bh(>sock->sk->sk_callback_lock);
> > +   }
> > +   down(>socket_lock);
> > +   radix_tree_delete(>socketpass_mappings, mappass->id);
> > +   sock_release(mappass->sock);
> > +   flush_workqueue(mappass->wq);
> > +   destroy_workqueue(mappass->wq);
> > +   kfree(mappass);
> > +   up(>socket_lock);
> 
> Can you raise the semaphore earlier, once the mapping is deleted from
> the tree?

Yes, I think it can.

> Also, why are you not locking the tree in pvcalls_back_accept()?

Good point! Although socket_lock is used to protect insertions and
deletions to socketpass_mappings and socket_mappings, many of the sites
that only access socket_mappings and socketpass_mappings without making
modifications are left unprotected at the moment. I'll fix that, and to
do it I'll move radix_tree_delete out of pvcalls_back_release_passive.

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Re: [Xen-devel] [PATCH v4 13/18] xen/pvcalls: implement release command

[Boris Ostrovsky]

> +
> +static int pvcalls_back_release_passive(struct xenbus_device *dev,
> + struct pvcalls_fedata *fedata,
> + struct sockpass_mapping *mappass)
> +{
> + if (mappass->sock->sk != NULL) {
> + write_lock_bh(>sock->sk->sk_callback_lock);
> + mappass->sock->sk->sk_user_data = NULL;
> + mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
> + write_unlock_bh(>sock->sk->sk_callback_lock);
> + }
> + down(>socket_lock);
> + radix_tree_delete(>socketpass_mappings, mappass->id);
> + sock_release(mappass->sock);
> + flush_workqueue(mappass->wq);
> + destroy_workqueue(mappass->wq);
> + kfree(mappass);
> + up(>socket_lock);

Can you raise the semaphore earlier, once the mapping is deleted from
the tree?

Also, why are you not locking the tree in pvcalls_back_accept()?

-boris


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[Xen-devel] [PATCH v4 13/18] xen/pvcalls: implement release command

[Stefano Stabellini]

Release both active and passive sockets. For active sockets, make sure
to avoid possible conflicts with the ioworker reading/writing to those
sockets concurrently. Set map->release to let the ioworker know
atomically that the socket will be released soon, then wait until the
ioworker finishes (flush_work).

Unmap indexes pages and data rings.

Signed-off-by: Stefano Stabellini 
CC: boris.ostrov...@oracle.com
CC: jgr...@suse.com
---
 drivers/xen/pvcalls-back.c | 70 ++
 1 file changed, 70 insertions(+)

diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
index be85977..afc9575 100644
--- a/drivers/xen/pvcalls-back.c
+++ b/drivers/xen/pvcalls-back.c
@@ -266,12 +266,82 @@ static int pvcalls_back_release_active(struct 
xenbus_device *dev,
   struct pvcalls_fedata *fedata,
   struct sock_mapping *map)
 {
+   disable_irq(map->irq);
+   if (map->sock->sk != NULL) {
+   write_lock_bh(>sock->sk->sk_callback_lock);
+   map->sock->sk->sk_user_data = NULL;
+   map->sock->sk->sk_data_ready = map->saved_data_ready;
+   write_unlock_bh(>sock->sk->sk_callback_lock);
+   }
+
+   atomic_set(>release, 1);
+   flush_work(>ioworker.register_work);
+
+   down(>socket_lock);
+   list_del(>list);
+   up(>socket_lock);
+
+   xenbus_unmap_ring_vfree(dev, map->bytes);
+   xenbus_unmap_ring_vfree(dev, (void *)map->ring);
+   unbind_from_irqhandler(map->irq, map);
+
+   sock_release(map->sock);
+   kfree(map);
+
+   return 0;
+}
+
+static int pvcalls_back_release_passive(struct xenbus_device *dev,
+   struct pvcalls_fedata *fedata,
+   struct sockpass_mapping *mappass)
+{
+   if (mappass->sock->sk != NULL) {
+   write_lock_bh(>sock->sk->sk_callback_lock);
+   mappass->sock->sk->sk_user_data = NULL;
+   mappass->sock->sk->sk_data_ready = mappass->saved_data_ready;
+   write_unlock_bh(>sock->sk->sk_callback_lock);
+   }
+   down(>socket_lock);
+   radix_tree_delete(>socketpass_mappings, mappass->id);
+   sock_release(mappass->sock);
+   flush_workqueue(mappass->wq);
+   destroy_workqueue(mappass->wq);
+   kfree(mappass);
+   up(>socket_lock);
+
return 0;
 }
 
 static int pvcalls_back_release(struct xenbus_device *dev,
struct xen_pvcalls_request *req)
 {
+   struct pvcalls_fedata *fedata;
+   struct sock_mapping *map, *n;
+   struct sockpass_mapping *mappass;
+   int ret = 0;
+   struct xen_pvcalls_response *rsp;
+
+   fedata = dev_get_drvdata(>dev);
+
+   list_for_each_entry_safe(map, n, >socket_mappings, list) {
+   if (map->id == req->u.release.id) {
+   ret = pvcalls_back_release_active(dev, fedata, map);
+   goto out;
+   }
+   }
+   mappass = radix_tree_lookup(>socketpass_mappings,
+   req->u.release.id);
+   if (mappass != NULL) {
+   ret = pvcalls_back_release_passive(dev, fedata, mappass);
+   goto out;
+   }
+
+out:
+   rsp = RING_GET_RESPONSE(>ring, fedata->ring.rsp_prod_pvt++);
+   rsp->req_id = req->req_id;
+   rsp->u.release.id = req->u.release.id;
+   rsp->cmd = req->cmd;
+   rsp->ret = ret;
return 0;
 }
 
-- 
1.9.1


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