Messages in this thread | | | Date | Sat, 16 Nov 2013 07:21:19 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH tip/core/rcu 11/14] bonding/bond_main: Apply ACCESS_ONCE() to avoid sparse false positive |
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On Sat, Nov 16, 2013 at 12:32:16PM +0800, Ding Tianhong wrote: > 于 2013/11/16 8:40, Paul E. McKenney 写道: > > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> > > > > The sparse checking for rcu_assign_pointer() was recently upgraded > > to reject non-__kernel address spaces. This also rejects __rcu, > > which is almost always the right thing to do. However, the uses in > > bond_change_active_slave() and __bond_release_one() are legitimate: > > They are assigning a pointer to an element from an RCU-protected list > > (or a NULL pointer), and all elements of this list are already visible > > to caller. > > > > This commit therefore silences these false positives either by laundering > > the pointers using ACCESS_ONCE() as suggested by Eric Dumazet and Josh > > Triplett, or by using RCU_INIT_POINTER() for NULL pointer assignments. > > I think it is fit for net-next.
Thank you!
If this is queued there, I would be happy to drop it from my tree. There are no dependencies on anything in my tree.
Thanx, Paul
> > Reported-by: kbuild test robot <fengguang.wu@intel.com> > > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > > Cc: Stephen Hemminger <stephen@networkplumber.org> > > Cc: "David S. Miller" <davem@davemloft.net> > > Cc: bridge@lists.linux-foundation.org > > Cc: netdev@vger.kernel.org > > --- > > drivers/net/bonding/bond_main.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c > > index 72df399c4ab3..bbd7fd3e46fe 100644 > > --- a/drivers/net/bonding/bond_main.c > > +++ b/drivers/net/bonding/bond_main.c > > @@ -890,7 +890,8 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active) > > if (new_active) > > bond_set_slave_active_flags(new_active); > > } else { > > - rcu_assign_pointer(bond->curr_active_slave, new_active); > > + /* Both --rcu and visible, so ACCESS_ONCE() is OK. */ > > + ACCESS_ONCE(bond->curr_active_slave) = new_active; > > } > > > > if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) { > > @@ -1801,7 +1802,7 @@ static int __bond_release_one(struct net_device *bond_dev, > > } > > > > if (all) { > > - rcu_assign_pointer(bond->curr_active_slave, NULL); > > + RCU_INIT_POINTER(bond->curr_active_slave, NULL); > > } else if (oldcurrent == slave) { > > /* > > * Note that we hold RTNL over this sequence, so there >
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