Patchwork [v4,net-next,2/3] bonding: fix __get_first_agg RCU usage

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Submitter Veaceslav Falico
Date Jan. 10, 2014, 10:59 a.m.
Message ID <>
Download mbox | patch
Permalink /patch/309254/
State Accepted
Delegated to: David Miller
Headers show


Veaceslav Falico - Jan. 10, 2014, 10:59 a.m.
Currently, the RCU read lock usage is just wrong - it gets the slave struct
under RCU and continues to use it when RCU lock is released.

However, it's still safe to do this cause we didn't need the
rcu_read_lock() initially - all of the __get_first_agg() callers are either
holding RCU read lock or the RTNL lock, so that we can't sync while in it.

Fixes: be79bd048 ("bonding: add RCU for bond_3ad_state_machine_handler()")
CC: Jay Vosburgh <>
CC: Andy Gospodarek <>
Signed-off-by: Veaceslav Falico <>

    v3 -> v4: add rcu_read_lock() to silence lockdep.
    v2 -> v3:
    Use the rcu primitives.
    v1 -> v2:
    Don't use RCU primitives as we can hold RTNL.

 drivers/net/bonding/bond_3ad.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)


diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index da0d7c5..b49f421 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -143,11 +143,13 @@  static inline struct bonding *__get_bond_by_port(struct port *port)
  * Return the aggregator of the first slave in @bond, or %NULL if it can't be
  * found.
+ * The caller must hold RCU or RTNL lock.
 static inline struct aggregator *__get_first_agg(struct port *port)
 	struct bonding *bond = __get_bond_by_port(port);
 	struct slave *first_slave;
+	struct aggregator *agg;
 	/* If there's no bond for this port, or bond has no slaves */
 	if (bond == NULL)
@@ -155,9 +157,10 @@  static inline struct aggregator *__get_first_agg(struct port *port)
 	first_slave = bond_first_slave_rcu(bond);
+	agg = first_slave ? &(SLAVE_AD_INFO(first_slave).aggregator) : NULL;
-	return first_slave ? &(SLAVE_AD_INFO(first_slave).aggregator) : NULL;
+	return agg;