I haven't looked at the code yet, but one restriction on ovsrcu_synchronize() is that the current thread can't have active pointers to any RCU-protected data (they can get freed). Is that safe here?
On Thu, Mar 19, 2015 at 01:43:54PM -0700, Jarno Rajahalme wrote: > Acked-by: Jarno Rajahalme <jrajaha...@nicira.com> > > Ben may also want to have a look, as commits 98de6bebb (dpif-netdev: Fix > another use-after-free in port_unref().) and 87400a3d4cc4a (dpif-netdev: Fix > use-after-free in port_unref().) by him have fixed earlier problems related > to this. I did not check the changes in these earlier patches, but it is > possible that ovsrcu_synchronize() is a more general solution to this > problem, as this makes the port lookups essentially RCU-protected. Maybe we > should document this fact in some comments? > > Jarno > > > On Mar 19, 2015, at 9:44 AM, Daniele Di Proietto <diproiet...@vmware.com> > > wrote: > > > > port_unref() shouldn't immediately free the port and close the netdev, > > because otherwise threads that still have a pointer to the port would > > crash. > > > > This commit fixes the problem by introducing an ovsrcu_synchronize() > > call in port_unref(). > > > > I chose not to use ovsrcu_postpone(), because postponing the removal of > > the 'netdev' would cause other issues, such as not being possible to > > reuse the same name for another netdev. > > > > Found the crash while developing new code. > > > > Signed-off-by: Daniele Di Proietto <diproiet...@vmware.com> > > --- > > lib/dpif-netdev.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c > > index f01fecb..2546e5e 100644 > > --- a/lib/dpif-netdev.c > > +++ b/lib/dpif-netdev.c > > @@ -994,6 +994,8 @@ port_unref(struct dp_netdev_port *port) > > int n_rxq = netdev_n_rxq(port->netdev); > > int i; > > > > + ovsrcu_synchronize(); > > + > > netdev_close(port->netdev); > > netdev_restore_flags(port->sf); > > > > -- > > 2.1.4 > > > > _______________________________________________ > > dev mailing list > > dev@openvswitch.org > > http://openvswitch.org/mailman/listinfo/dev > > _______________________________________________ > dev mailing list > dev@openvswitch.org > http://openvswitch.org/mailman/listinfo/dev _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
