[ovs-dev] [backport branch-2.3] route-table: Make route-table module thread-safe.

[Ben Pfaff]

On Sun, Jul 20, 2014 at 12:43:41AM -0700, Alex Wang wrote:
> From: Ryan Wilson <wryan at nicira.com>
> 
> Since the use of xcache, the netdev struct can be freed by the
> revalidator threads.  This fact also makes the following race possible:
> 
> 1. Consider there is a gre tunnel, and datapath flows that go through
>    the tunnel.  Now, assume user deletes the tunnel port.
> 2. The main thread closes all of its references to the corresponding
>    netdev struct.
> 3. If the ukey for the tunnel datapath flows hold the last reference
>    to the old port's netdev, the revalidator will then close it
>    and remove the netlink notifier struct (if the netdev is the last
>    vport netdev).
> 4. However, if the main thread executes the netdev_vport_run(), and
>    sees the existence of netlink notifier struct (before revalidator
>    frees it), it will try polling updates from the notifier socket.
>    And when it polls the socket fd, the fd has already been freed,
>    and poll will keep failing with "Bad file descriptor".
> 
> This race has already been fixed on master by commit 3c27dbe6 (route
> -table: Make route-table module thread-safe.).  This commit backports
> it to branch-2.3.
> 
> VMware-BZ: #1287360
> 
> Signed-off-by: Alex Wang <alexw at nicira.com>

This should reproduce Ryan's Signed-off-by from the original commit.

Acked-by: Ben Pfaff <blp at nicira.com>