bonding 802.3ad: Fix the state machine locking v2

Changes since v1:
* Clarify an unclear comment
* Move a (possible) name change to a separate patch

The ad_rx_machine, ad_periodic_machine and ad_port_selection_logic
functions all inspect and alter common fields within the port structure.
Previous to this patch, only the ad_rx_machines were mutexed, and the
periodic and port_selection could run unmutexed against an ad_rx_machine
trigged by an arriving LACPDU.

This patch remedies the situation by protecting all the state machines
from concurrency. This is accomplished by locking around all the state
machines for a given port, which are executed at regular intervals; and
the ad_rx_machine when handling an incoming LACPDU.

Signed-off-by: Nils Carlson <nils.carlson@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 5 deletions

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index 1024ae158227..de30c8d6301e 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -1025,9 +1025,6 @@ static void ad_rx_machine(struct lacpdu *lacpdu, struct port *port)
 {
         rx_states_t last_state;
 
-        // Lock to prevent 2 instances of this function to run simultaneously(rx interrupt and periodic machine callback)
-        __get_rx_machine_lock(port);
-
         // keep current State Machine state to compare later if it was changed
         last_state = port->sm_rx_state;
 
@@ -1133,7 +1130,6 @@ static void ad_rx_machine(struct lacpdu *lacpdu, struct port *port)
                                 pr_err("%s: An illegal loopback occurred on adapter (%s).\n"
                                        "Check the configuration to verify that all adapters are connected to 802.3ad compliant switch ports\n",
                                        port->slave->dev->master->name, port->slave->dev->name);
-                                __release_rx_machine_lock(port);
                                 return;
                         }
                         __update_selected(lacpdu, port);
@@ -1153,7 +1149,6 @@ static void ad_rx_machine(struct lacpdu *lacpdu, struct port *port)
                         break;
                 }
         }
-        __release_rx_machine_lock(port);
 }
 
 /**
@@ -2155,6 +2150,12 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
                         goto re_arm;
                 }
 
+                /* Lock around state machines to protect data accessed
+                 * by all (e.g., port->sm_vars).  ad_rx_machine may run
+                 * concurrently due to incoming LACPDU.
+                 */
+                __get_rx_machine_lock(port);
+
                 ad_rx_machine(NULL, port);
                 ad_periodic_machine(port);
                 ad_port_selection_logic(port);
@@ -2164,6 +2165,8 @@ void bond_3ad_state_machine_handler(struct work_struct *work)
                 // turn off the BEGIN bit, since we already handled it
                 if (port->sm_vars & AD_PORT_BEGIN)
                         port->sm_vars &= ~AD_PORT_BEGIN;
+
+                __release_rx_machine_lock(port);
         }
 
 re_arm:
@@ -2200,7 +2203,10 @@ static void bond_3ad_rx_indication(struct lacpdu *lacpdu, struct slave *slave, u
                 case AD_TYPE_LACPDU:
                         pr_debug("Received LACPDU on port %d\n",
                                  port->actor_port_number);
+                        /* Protect against concurrent state machines */
+                        __get_rx_machine_lock(port);
                         ad_rx_machine(lacpdu, port);
+                        __release_rx_machine_lock(port);
                         break;
 
                 case AD_TYPE_MARKER: